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Saturday, August 6, 2016
Tuesday, August 18, 2015
Voltage Transformer Basics
One of the main reasons that we use alternating AC
voltages and currents in our homes and workplace’s is that AC supplies
can be easily generated at a convenient voltage, transformed (hence the
name transformer) into much higher voltages and then distributed around
the country using a national grid of pylons and cables over very long
distances.
The reason for transforming the voltage to a much higher level is
that higher distribution voltages implies lower currents for the same
power and therefore lower I2R losses along the networked grid
of cables. These higher AC transmission voltages and currents can then
be reduced to a much lower, safer and usable voltage level where it can
be used to supply electrical equipment in our homes and workplaces, and
all this is possible thanks to the basic Voltage Transformer.
A Typical Voltage Transformer
The Voltage Transformer can be thought of as an
electrical component rather than an electronic component. A transformer
basically is very simple static (or stationary) electro-magnetic passive
electrical device that works on the principle of Faraday’s law of
induction by converting electrical energy from one value to another.
The transformer does this by linking together two or more electrical
circuits using a common oscillating magnetic circuit which is produced
by the transformer itself. A transformer operates on the principals of
“electromagnetic induction”, in the form of Mutual Induction.
Mutual induction is the process by which a coil of wire magnetically
induces a voltage into another coil located in close proximity to it.
Then we can say that transformers work in the “magnetic domain”, and
transformers get their name from the fact that they “transform” one
voltage or current level into another.
Transformers are capable of either increasing or decreasing the
voltage and current levels of their supply, without modifying its
frequency, or the amount of Electrical Power being transferred from one winding to another via the magnetic circuit.
A single phase voltage transformer basically consists of two
electrical coils of wire, one called the “Primary Winding” and another
called the “Secondary Winding”. For this tutorial we will define the
“primary” side of the transformer as the side that usually takes power,
and the “secondary” as the side that usually delivers power. In a
single-phase voltage transformer the primary is usually the side with
the higher voltage.
These two coils are not in electrical contact with each other but are
instead wrapped together around a common closed magnetic iron circuit
called the “core”. This soft iron core is not solid but made up of
individual laminations connected together to help reduce the core’s
losses.
The two coil windings are electrically isolated from each other but
are magnetically linked through the common core allowing electrical
power to be transferred from one coil to the other. When an electric
current passed through the primary winding, a magnetic field is
developed which induces a voltage into the secondary winding as shown.
Single Phase Voltage Transformer
In other words, for a transformer there is no direct electrical
connection between the two coil windings, thereby giving it the name
also of an Isolation Transformer. Generally, the
primary winding of a transformer is connected to the input voltage
supply and converts or transforms the electrical power into a magnetic
field. While the job of the secondary winding is to convert this
alternating magnetic field into electrical power producing the required
output voltage as shown.
Transformer Construction (single-phase)
- Where:
- VP - is the Primary Voltage
- VS - is the Secondary Voltage
- NP - is the Number of Primary Windings
- NS - is the Number of Secondary Windings
- Φ (phi) - is the Flux Linkage
Notice that the two coil windings are not electrically connected but
are only linked magnetically. A single-phase transformer can operate to
either increase or decrease the voltage applied to the primary winding.
When a transformer is used to “increase” the voltage on its secondary
winding with respect to the primary, it is called a Step-up transformer. When it is used to “decrease” the voltage on the secondary winding with respect to the primary it is called a Step-down transformer.
However, a third condition exists in which a transformer produces the
same voltage on its secondary as is applied to its primary winding. In
other words, its output is identical with respect to voltage, current
and power transferred. This type of transformer is called an “Impedance
Transformer” and is mainly used for impedance matching or the isolation
of adjoining electrical circuits.
The difference in voltage between the primary and the secondary
windings is achieved by changing the number of coil turns in the primary
winding ( NP ) compared to the number of coil turns on the secondary winding ( NS ).
As the transformer is basically a linear device, a ratio now exists
between the number of turns of the primary coil divided by the number of
turns of the secondary coil. This ratio, called the ratio of
transformation, more commonly known as a transformers “turns ratio”, ( TR ).
This turns ratio value dictates the operation of the transformer and
the corresponding voltage available on the secondary winding.
It is necessary to know the ratio of the number of turns of wire on
the primary winding compared to the secondary winding. The turns ratio,
which has no units, compares the two windings in order and is written
with a colon, such as 3:1 (3-to-1). This means
in this example, that if there are 3 volts on the primary winding there
will be 1 volt on the secondary winding, 3 volts-to-1 volt. Then we can
see that if the ratio between the number of turns changes the resulting
voltages must also change by the same ratio, and this is true.
Transformers are all about “ratios”. The ratio of the primary to the
secondary, the ratio of the input to the output, and the turns ratio of
any given transformer will be the same as its voltage ratio. In other
words for a transformer: “turns ratio = voltage ratio”. The actual
number of turns of wire on any winding is generally not important, just
the turns ratio and this relationship is given as:
A Transformers Turns Ratio
Assuming an ideal transformer and the phase angles: ΦP ≡ ΦS
Note that the order of the numbers when expressing a transformers turns ratio value is very important as the turns ratio 3:1 expresses a very different transformer relationship and output voltage than one in which the turns ratio is given as: 1:3.
Transformer Basics Example No1
A voltage transformer has 1500 turns of wire on its primary coil and
500 turns of wire for its secondary coil. What will be the turns ratio
(TR) of the transformer.
This ratio of 3:1 (3-to-1) simply means
that there are three primary windings for every one secondary winding.
As the ratio moves from a larger number on the left to a smaller number
on the right, the primary voltage is therefore stepped down in value as
shown.
Transformer Basics Example No2
If 240 volts rms is applied to the primary winding of the same
transformer above, what will be the resulting secondary no load voltage.
Again confirming that the transformer is a “step-down transformer as
the primary voltage is 240 volts and the corresponding secondary voltage
is lower at 80 volts.
Then the main purpose of a transformer is to transform voltages at
preset ratios and we can see that the primary winding has a set amount
or number of windings (coils of wire) on it to suit the input voltage.
If the secondary output voltage is to be the same value as the input
voltage on the primary winding, then the same number of coil turns must
be wound onto the secondary core as there are on the primary core giving
an even turns ratio of 1:1 (1-to-1). In other words, one coil turn on the secondary to one coil turn on the primary.
If the output secondary voltage is to be greater or higher than the
input voltage, (step-up transformer) then there must be more turns on
the secondary giving a turns ratio of 1:N (1-to-N), where N
represents the turns ratio number. Likewise, if it is required that the
secondary voltage is to be lower or less than the primary, (step-down
transformer) then the number of secondary windings must be less giving a
turns ratio of N:1 (N-to-1).
Transformer Action
We have seen that the number of coil turns on the secondary winding
compared to the primary winding, the turns ratio, affects the amount of
voltage available from the secondary coil. But if the two windings are
electrically isolated from each other, how is this secondary voltage
produced?
We have said previously that a transformer basically consists of two
coils wound around a common soft iron core. When an alternating voltage
( VP ) is applied to the primary coil, current flows through the coil which in turn sets up a magnetic field around itself, called mutual inductance, by this current flow according to Faraday’s Law
of electromagnetic induction. The strength of the magnetic field builds
up as the current flow rises from zero to its maximum value which is
given as dΦ/dt.
As the magnetic lines of force setup by this electromagnet expand
outward from the coil the soft iron core forms a path for and
concentrates the magnetic flux. This magnetic flux links the turns of
both windings as it increases and decreases in opposite directions under
the influence of the AC supply.
However, the strength of the magnetic field induced into the soft
iron core depends upon the amount of current and the number of turns in
the winding. When current is reduced, the magnetic field strength
reduces.
When the magnetic lines of flux flow around the core, they pass
through the turns of the secondary winding, causing a voltage to be
induced into the secondary coil. The amount of voltage induced will be
determined by: N.dΦ/dt (Faraday’s Law), where N is the number of coil turns. Also this induced voltage has the same frequency as the primary winding voltage.
Then we can see that the same voltage is induced in each coil turn of
both windings because the same magnetic flux links the turns of both
the windings together. As a result, the total induced voltage in each
winding is directly proportional to the number of turns in that winding.
However, the peak amplitude of the output voltage available on the
secondary winding will be reduced if the magnetic losses of the core are
high.
If we want the primary coil to produce a stronger magnetic field to
overcome the cores magnetic losses, we can either send a larger current
through the coil, or keep the same current flowing, and instead increase
the number of coil turns ( NP ) of
the winding. The product of amperes times turns is called the
“ampere-turns”, which determines the magnetising force of the coil.
So assuming we have a transformer with a single turn in the primary,
and only one turn in the secondary. If one volt is applied to the one
turn of the primary coil, assuming no losses, enough current must flow
and enough magnetic flux generated to induce one volt in the single turn
of the secondary. That is, each winding supports the same number of
volts per turn.
As the magnetic flux varies sinusoidally, Φ = Φmax sinωt, then the basic relationship between induced emf, ( E ) in a coil winding of N turns is given by:
emf = turns x rate of change
- Where:
- ƒ - is the flux frequency in Hertz, = ω/2π
- Ν - is the number of coil windings.
- Φ - is the flux density in webers
This is known as the Transformer EMF Equation. For the primary winding emf, N will be the number of primary turns, ( NP ) and for the secondary winding emf, N will be the number of secondary turns, ( NS ).
Also please note that as transformers require an alternating magnetic
flux to operate correctly, transformers cannot therefore be used to
transform or supply DC voltages or currents, since the magnetic field
must be changing to induce a voltage in the secondary winding. In other
words, Transformers DO NOT Operate on DC Voltages, ONLY AC.
If a transformers primary winding was connected to a DC supply, the
inductive reactance of the winding would be zero as DC has no frequency,
so the effective impedance of the winding will therefore be very low
and equal only to the resistance of the copper used. Thus the winding
will draw a very high current from the DC supply causing it to overheat
and eventually burn out, because as we know I = V/R.
Transformer Basics Example No3
A single phase transformer has 480 turns on the primary winding and
90 turns on the secondary winding. The maximum value of the magnetic
flux density is 1.1T when 2200 volts, 50Hz is applied to the transformer
primary winding. Calculate:
a). The maximum flux in the core.
b). The cross-sectional area of the core.
c). The secondary induced emf.
Electrical Power in a Transformer
Another one of the transformer basics parameters is its power rating. Transformers are rated in Volt-amperes, ( VA ), or in larger units of Kilo Volt-amperes, ( kVA ).
In an ideal transformer (ignoring any losses), the power available in
the secondary winding will be the same as the power in the primary
winding, they are constant wattage devices and do not change the power
only the voltage to current ratio. Thus, in an ideal transformer the Power Ratio is equal to one (unity) as the voltage, V multiplied by the current, I will remain constant.
That is the electric power at one voltage/current level on the
primary is “transformed” into electric power, at the same frequency, to
the same voltage/current level on the secondary side. Although the
transformer can step-up (or step-down) voltage, it cannot step-up power.
Thus, when a transformer steps-up a voltage, it steps-down the current
and vice-versa, so that the output power is always at the same value as
the input power. Then we can say that primary power equals secondary
power, ( PP = PS ).
Power in a Transformer
Where: ΦP is the primary phase angle and ΦS is the secondary phase angle.
Note that since power loss is proportional to the square of the current being transmitted, that is: I2R,
increasing the voltage, let’s say doubling ( ×2 ) the voltage would
decrease the current by the same amount, ( ÷2 ) while delivering the
same amount of power to the load and therefore reducing losses by factor
of 4. If the voltage was increased by a factor of 10, the current would
decrease by the same factor reducing overall losses by factor of 100.
Transformer Basics – Efficiency
A transformer does not require any moving parts to transfer energy.
This means that there are no friction or windage losses associated with
other electrical machines. However, transformers do suffer from other
types of losses called “copper losses” and “iron losses” but generally
these are quite small.
Copper losses, also known as I2R
loss is the electrical power which is lost in heat as a result of
circulating the currents around the transformers copper windings, hence
the name. Copper losses represents the greatest loss in the operation of
a transformer. The actual watts of power lost can be determined (in
each winding) by squaring the amperes and multiplying by the resistance
in ohms of the winding (I2R).
Iron losses, also known as hysteresis is the lagging of the magnetic
molecules within the core, in response to the alternating magnetic flux.
This lagging (or out-of-phase) condition is due to the fact that it
requires power to reverse magnetic molecules; they do not reverse until
the flux has attained sufficient force to reverse them.
Their reversal results in friction, and friction produces heat in the
core which is a form of power loss. Hysteresis within the transformer
can be reduced by making the core from special steel alloys.
The intensity of power loss in a transformer determines its
efficiency. The efficiency of a transformer is reflected in power
(wattage) loss between the primary (input) and secondary (output)
windings. Then the resulting efficiency of a transformer is equal to the
ratio of the power output of the secondary winding, PS to the power input of the primary winding, PP and is therefore high.
An ideal transformer is 100% efficient because it delivers all the
energy it receives. Real transformers on the other hand are not 100%
efficient and at full load, the efficiency of a transformer is between
94% to 96% which is quiet good. For a transformer operating with a
constant voltage and frequency with a very high capacity, the efficiency
may be as high as 98%. The efficiency, η of a transformer is given as:
Transformer Efficiency
where: Input, Output and Losses are all expressed in units of power.
Generally when dealing with transformers, the primary watts are called “volt-amps”, VA to differentiate them from the secondary watts. Then the efficiency equation above can be modified to:
It is sometimes easier to remember the relationship between the
transformers input, output and efficiency by using pictures. Here the
three quantities of VA, W and η
have been superimposed into a triangle giving power in watts at the top
with volt-amps and efficiency at the bottom. This arrangement
represents the actual position of each quantity in the efficiency
formulas.
Transformer Efficiency Triangle
and transposing the above triangle quantities gives us the following combinations of the same equation:
Then, to find Watts (output) = VA x eff., or to find VA (input) = W/eff., or to find Efficiency, eff. = W/VA, etc.
Transformer Basics Summary
Then to summarise this transformer basics tutorial. A Transformer
changes the voltage level (or current level) on its input winding to
another value on its output winding using a magnetic field. A
transformer consists of two electrically isolated coils and operates on
Faraday’s principal of “mutual induction”, in which an EMF is induced in
the transformers secondary coil by the magnetic flux generated by the
voltages and currents flowing in the primary coil winding.
Both the primary and secondary coil windings are wrapped around a
common soft iron core made of individual laminations to reduce eddy
current and power losses. The primary winding of the transformer is
connected to the AC power source which must be sinusoidal in nature,
while the secondary winding supplies power to the load.
We can represent the transformer in block diagram form as follows:
Basic Representation of the Transformer
The ratio of the transformers primary and secondary windings with
respect to each other produces either a step-up voltage transformer or a
step-down voltage transformer with the ratio between the number of
primary turns to the number of secondary turns being called the “turns
ratio” or “transformer ratio”.
If this ratio is less than unity, n < 1 then NS is greater than NP and the transformer is classed as a step-up transformer. If this ratio is greater than unity, n > 1, that is NP is greater than NS,
the transformer is classed as a step-down transformer. Note that single
phase step-down transformer can also be used as a step-up transformer
simply by reversing its connections and making the low voltage winding
its primary, and vice versa as long as the transformer is operated
within its original VA design rating.
If the turns ratio is equal to unity, n = 1
then both the primary and secondary have the same number of windings,
therefore the voltages and currents are the same for both windings.
This type of transformer is classed as an isolation transformer as
both the primary and secondary windings of the transformer have the same
number of volts per turn. The efficiency of a transformer is the ratio
of the power it delivers to the load to the power it absorbs from the
supply. In an ideal transformer there are no losses so no loss of power
then Pin = Pout.
In the next tutorial to do with Transformer Basics, we will look at the physical Construction of a Transformer and see the different magnetic core types and laminations used to support the primary and secondary windings.
Sunday, August 16, 2015
What is the use of integration and differentiation?
What is the use of integration and differentiation?
Let us get into this with all interest. Yes integration is a reverse process of differentiation.
First let us put the question why do we need such a mathematical process called integration. Actually integration is nothing but the summing up of a lot, some million and million items.
Let me explain how.
Suppose you want to find the volume of a cone of radius r and height h.
Let the cone be seated such that its vertex get coincided with the origin and its height be along the x -axis.
In case of a cylinder the radius will be the same at all heights and so if you consider a small part both the sides of that part will have the same radius and so no problem in finding the volume.
But in the case of the cone, as we move away from the origin along x-axis the radius of the cone will be gradually increasing.
So as you consider a slice any where in the cone both the sides of the slice will not definitely have same radius. Is that ok?
Now calculus comes into play.
You choose a small slice in such a way that both the sides of the slice would have almost the same radius. It is possible only when you have a slice of negligible thickness. Such negligible thickness is denoted mathematically denoted as dx which means delta x tending to zero.
Once again note down the statement: delta x tending to zero. This means delta x is very so near to zero but not zero.
With such....... thickness, both sides of the slice would have the same radius.Let the slice of thickness dx be chosen at a distance x from the origin and let the radius of the slice be y at that position. Then the volume of our slice will be pi y^2 dx. Now imagine! Such slices, innumerable in number, can be got in the cone right moving from the origin and extending upto the total length (height) h of the cone. So we must collect all such slices and add their volumes to get the actual or total volume of the cone.
So we integrate the term pi y^2 dx within the limits of x ie 0 to h.
Now it becomes more essential to replace y interms of x. How can we do this? By using similar triangle concept, the ratio of the corresponding sides will be the same. So y/x = r/h
From this we can easily have y as (r/h) x.
Now replacing y we get the expression to be integrated (usually named as integrand) as pi (r/h)^2 x^2 dx. The formula for integral of x^n dx is given as x^(n+1) /(n+1).
So following this we get the integral value as pi(r/h)^2 (x^3 /3).
Next important step is supplying limit of x.
First upper limit h. This would give a value of pi(r/h)^2 (h^3 /3)
With lower limit 0, the value would become 0
Now the difference between these two values will be the required volume of the cone.
That comes to be 1/3 pi r^2 h. (cancelling h^2)
So interesting! See how much helpful the technique of integration in finding the volume of the cone!
By differentiation, we chop things into finer and by integration we collect all such finer.
Hope you have got a gist of the tremendous usage of the branch of mathematics, named as calculus.
First let us put the question why do we need such a mathematical process called integration. Actually integration is nothing but the summing up of a lot, some million and million items.
Let me explain how.
Suppose you want to find the volume of a cone of radius r and height h.
Let the cone be seated such that its vertex get coincided with the origin and its height be along the x -axis.
In case of a cylinder the radius will be the same at all heights and so if you consider a small part both the sides of that part will have the same radius and so no problem in finding the volume.
But in the case of the cone, as we move away from the origin along x-axis the radius of the cone will be gradually increasing.
So as you consider a slice any where in the cone both the sides of the slice will not definitely have same radius. Is that ok?
Now calculus comes into play.
You choose a small slice in such a way that both the sides of the slice would have almost the same radius. It is possible only when you have a slice of negligible thickness. Such negligible thickness is denoted mathematically denoted as dx which means delta x tending to zero.
Once again note down the statement: delta x tending to zero. This means delta x is very so near to zero but not zero.
With such....... thickness, both sides of the slice would have the same radius.Let the slice of thickness dx be chosen at a distance x from the origin and let the radius of the slice be y at that position. Then the volume of our slice will be pi y^2 dx. Now imagine! Such slices, innumerable in number, can be got in the cone right moving from the origin and extending upto the total length (height) h of the cone. So we must collect all such slices and add their volumes to get the actual or total volume of the cone.
So we integrate the term pi y^2 dx within the limits of x ie 0 to h.
Now it becomes more essential to replace y interms of x. How can we do this? By using similar triangle concept, the ratio of the corresponding sides will be the same. So y/x = r/h
From this we can easily have y as (r/h) x.
Now replacing y we get the expression to be integrated (usually named as integrand) as pi (r/h)^2 x^2 dx. The formula for integral of x^n dx is given as x^(n+1) /(n+1).
So following this we get the integral value as pi(r/h)^2 (x^3 /3).
Next important step is supplying limit of x.
First upper limit h. This would give a value of pi(r/h)^2 (h^3 /3)
With lower limit 0, the value would become 0
Now the difference between these two values will be the required volume of the cone.
That comes to be 1/3 pi r^2 h. (cancelling h^2)
So interesting! See how much helpful the technique of integration in finding the volume of the cone!
By differentiation, we chop things into finer and by integration we collect all such finer.
Hope you have got a gist of the tremendous usage of the branch of mathematics, named as calculus.
Explain why the moon has no atmosphere..?
Moon has no atmosphere because the value of acceleration due to gravity
‘g’ on the surface of moon is small. Therefore, the value of escape
velocity on the surface of moon is small. The value of r.m.s. velocity
of the molecules of different gases is much above the value of escape
velocity on moon. That is why all the molecules of gases escaped and
there is no atmosphere on moon.
Friday, August 14, 2015
What is force?
In physics, a force is any interaction that, when unopposed, will change the motion of an object. In other words, a force
can cause an object with mass to change its velocity (which includes to
begin moving from a state of rest), i.e., to accelerate.
What Is the Difference Between Mass and Weight?
Comparison of Mass and Weight
| Mass is a property of matter. The mass of an object is the same everywhere, | Weight depends on the effect of gravity. Weight varies according to location. |
| Mass can never be zero. | Weight can be zero if no gravity acts upon an object, as in space. |
| Mass does not change according to location. | Weight increases or decreases with higher or lower gravity. |
| Mass is a scalar quantity. It has magnitude. | Weight is a vector quantity. It has magnitude and is directed toward the center of the Earth or other gravity well. |
| Mass may be measured using an ordinary balance. | Weight is measured using a spring balance. |
| Mass usually is measured in grams and kilograms. | Weight often is measured in newtons, a unit of force. |
Sunday, August 2, 2015
Math Puzzle Questions
1. What is come in place of question mark (?) in the following series?
(a) HS
(b) IT
(c) IS
(d) HT
Solution:
2. If A is substituted by 4, B by 3, C by 2, D by 4, E by 3, F by 2 and so on, then what will be total of the numerical values of the letters of the word SICK?
(a) 11
(b) 12
(c) 10
(d) 9
Solution:
Total value = 4 + 2 + 2 + 3 = 11.
Answer: (a)
3. Four of the following five are alike in a certain way and hence form a group. Which one does not belong to the group?
(a) 52
(b) 70
(c) 48
(d) 68
Solution:All the numbers are multiple of 4, except 70.
Answer: (b)
4. If U is denoted by 7, M by 2, I by 5, O by 1, K by 8 and J by 4, then what will be the numeric form of the word MOUJIK when written in the reverse order?
(a) 217458
(b) 845712
(c) 854712
(d) 857412
Solution:
217458 is the number.
Now reverse the number 854712
Answer: (c)
5. How many letters of the word FAINTS, will their order in the word and that when the letters are arranged in the alphabetical order, remain the same?
(a) Two
(b) One
(c) Three
(d) Nil
Solution:
When the letters are arranged in the alphabetical order, two remains the same.
Answer: (a)
6. In a certain code GARNISH is written as RGAINHS. How will GENIOUS be written in that code?
(a) NEGOISU
(b) NGEOISU
(c) NGESUOI
(d) NEGSUOI
Solution:
So now, GENIOUS be written as;
Answer: (b)
7. How many such pairs of letters are there in the word MISPLACE each of which has as many letters between its two letters in the word as there are between them in the English alphabet?
(a) One
(b) Nil
(c) Two
(d) Three
Solution:
Answer: (c)
8. In a certain code INKER is written as GLLGT and GLIDE is written as EJJFG. How will JINKS be written in that code?
(a) GFOMU
(b) HGMMU
(c) HGOGH
(d) HGOMU
Solution:
As,
And,
Similarly, JINKS be written as;
Answer: (d)
9. If ‘AND’ is written as ‘EQF’ and ‘THE’ as ‘XKG’ then how will ‘COM’ be written?
(a) HRO
(b) GQO
(c) GRO
(d) GRN
Solution:
As,
And,
Similarly, ‘COM’ be written as;
Answer: (c)
10. Four of the following five are alike in a certain way based on the positions of their elements in the English alphabet and hence form a group. Which one does not belong to the group?
(a) UQ
(b) KG
(c) SO
(d) QL
Solution:
QL
Answer: (d)
(a) HS
(b) IT
(c) IS
(d) HT
Solution:
2. If A is substituted by 4, B by 3, C by 2, D by 4, E by 3, F by 2 and so on, then what will be total of the numerical values of the letters of the word SICK?
(a) 11
(b) 12
(c) 10
(d) 9
Solution:
Total value = 4 + 2 + 2 + 3 = 11.
Answer: (a)
3. Four of the following five are alike in a certain way and hence form a group. Which one does not belong to the group?
(a) 52
(b) 70
(c) 48
(d) 68
Solution:All the numbers are multiple of 4, except 70.
Answer: (b)
4. If U is denoted by 7, M by 2, I by 5, O by 1, K by 8 and J by 4, then what will be the numeric form of the word MOUJIK when written in the reverse order?
(a) 217458
(b) 845712
(c) 854712
(d) 857412
Solution:
217458 is the number.
Now reverse the number 854712
Answer: (c)
5. How many letters of the word FAINTS, will their order in the word and that when the letters are arranged in the alphabetical order, remain the same?
(a) Two
(b) One
(c) Three
(d) Nil
Solution:
When the letters are arranged in the alphabetical order, two remains the same.
Answer: (a)
6. In a certain code GARNISH is written as RGAINHS. How will GENIOUS be written in that code?
(a) NEGOISU
(b) NGEOISU
(c) NGESUOI
(d) NEGSUOI
Solution:
So now, GENIOUS be written as;
Answer: (b)
7. How many such pairs of letters are there in the word MISPLACE each of which has as many letters between its two letters in the word as there are between them in the English alphabet?
(a) One
(b) Nil
(c) Two
(d) Three
Solution:
8. In a certain code INKER is written as GLLGT and GLIDE is written as EJJFG. How will JINKS be written in that code?
(a) GFOMU
(b) HGMMU
(c) HGOGH
(d) HGOMU
Solution:
As,
And,
Similarly, JINKS be written as;
Answer: (d)
9. If ‘AND’ is written as ‘EQF’ and ‘THE’ as ‘XKG’ then how will ‘COM’ be written?
(a) HRO
(b) GQO
(c) GRO
(d) GRN
Solution:
As,
And,
Similarly, ‘COM’ be written as;
Answer: (c)
10. Four of the following five are alike in a certain way based on the positions of their elements in the English alphabet and hence form a group. Which one does not belong to the group?
(a) UQ
(b) KG
(c) SO
(d) QL
Solution:
QL
Answer: (d)
Sunday, January 19, 2014
Physics Objective Question
Objective Question Of Physics
1.
|
A certain current on passing through a galvanometer produces a deflection of 100 divisions. When a shunt of one ohm is connected, the deflection reduces to 1 division. The galvanometer resistance is
(A) 100 W
(B) 99 W
(C) 10 W
(D) 9.9 W
|
Answer: (B)
|
2.
|
A closed organ pipe and an open organ pipe of same length produce 2 beats/second while vibrating in their fundamental modes. The length of the open organ pipe is halved and that of closed pipe is doubled. Then, the number of beats produced per second while vibrating in the fundamental mode is ______.
(A) 8
(B) 7
(C) 2
(D) 6
|
Answer: (B)
|
3.
|
A convex and a concave lens separated by distance d are then put in contact. The focal length of the combination
(A) decreases
(B) increases
(C) becomes 0
(D) remains the same
|
Answer: (B)
|
4.
|
A current of 5A is flowing at 220 V in the primary coil of a transformer. If the voltage produced in the secondary coil is 2200 V and 50% of power is lost, then the current in the secondary will be
(A) 2.5 A
(B) 5 A
(C) 0.25 A
(D) 0.5 A
|
Answer: (C)
|
6.
|
A horizontal metal wire is carrying an electric current from the north to the south. Using a uniform magnetic field, it is to be prevented from falling under gravity. The direction of this magnetic field should be towards the______.
(A) east
(B) west
(C) north
(D) south
|
Answer: (A)
|
8.
|
A metal wire is subjected to a constant potential difference. When the temperature of the metal wire increases, the drift velocity of the electron in it
(A) increases, thermal velocity of the electron decreases
(B) decreases, thermal velocity of the electron decreases
(C) increases, thermal velocity of the electron increases
(D) decreases, thermal velocity of the electron increases
|
Answer: (D)
|
9.
|
A motorboat covers a given distance in 6 hours moving downstream on a river. It covers the same distance in 10 hours moving upstream. The time it takes to cover the same distance in still water is ______.
(A) 6.5 hours
(B) 8 hours
(C) 9hours
(D) 7.5 hours
|
Answer: (D)
|
10.
|
A radioactive sample S1 having the activity A1 has twice the number of nuclei as another sample S2 of activity A2. If A2 = 2A1, then the ratio of half life of S1 to the half life of S2is
(A) 0.25
(B) 0.75
(C) 4
(D) 2
|
Answer: (C)
|
11.
|
A body of mass M hits normally a rigid wall with velocity V and bounces back with the same velocity. The impulse experienced by the body is
(A) Zero (B) MV (C) 1.5 MV (D) 2 MV |
Answer: (D)
|
12.
|
A body projected vertically from the earth reaches a height equal to earth's radius before returning to the earth. The power exerted by the gravitational force is greatest
(A) At the instant just after the body is projected (B) At the highest position of the body (C) At the instant just before the body hits the earth (D) It remains constant all through |
Answer: (C)
|
13.
|
A charge Q is enclosed by a Gaussian spherical surface of radius R. If the radius is doubled, then the outward electric flux will
(A) Be doubled (B) Increase four times (C) Be reduced to half (D) Remain the same |
Answer: (D)
|
14.
|
A convex lens of focal length 30 cm produces 5 times magnified real image of an object. What is the object distance?
(A) 36 cm (B) 25 cm (C) 30 cm (D) 150 cm |
Answer: (A)
|
15.
|
A count rate meter shows a count of 240 per minute from a given radioactive source. One hour later the meter shows a count rate of 30 per minute. The half-life of the source is _______.
(A) 20 min (B) 30 min (C) 80 min (D) 120 min |
Answer: (A)
|
2.
|
Two beams of red and violet colours are made to pass separately through a prism of A = 60°. In the minimum deviation position, the angle of refraction inside the prism will be
(A) greater for violet colour
(B) 30° for both the colours
(C) greater for red colour
(D) equal but not 30° for both the colours
|
Answer: (B)
| ||||
3.
|
92U235 undergoes successive disintegrations with the end product of 82Pb203. The Number of a and b particles emitted are
(A) a = 6, b = 4
(B) a = 6, b = 0
(C) a = 8, b = 6
(D) a = 3, b = 3
|
Answer: (C)
| ||||
4.
|
A bat flies at a steady speed of 4 ms-1 emitting a sound of f = 90 ´ 103 Hz. It is flying horizontally towards a vertical wall. The frequency of the reflected sound as detected by the bat will be _____.
(Take velocity of sound in air as 330 ms-1).
(A) 92.1 ´ 103 Hz
(B) 89.1 ´ 103 Hz
(C) 88.1 ´ 103 Hz
(D) 87.1 ´ 103 Hz
|
Answer: (A)
| ||||
5.
|
A battery of e.m.f. E has an internal resistance 'r'. A variable resistance R is connected to the terminals of the battery. A current I is drawn from the battery. V is the terminal P.D. lf R alone is gradually reduced to zero, which of the following best describes I and V?
(A) I approaches E / r, V approaches E
(B) I approaches infinity, V approaches E
(C) I approaches zero, V approaches E
(D) I approaches E / r, V approaches zero
|
Answer: (D)
| ||||
6.
|
A boat has green light of wavelength l = 500 nm on the mast. What wavelength would be measured and what colour would be observed for this light as seen by a diver submerged in water by the side of the boat? Given nw = 4/3.
(A) Green of wavelength 500 nm
(B) Blue of wavelength 376 nm
(C) Green of wavelength 376 nm
(D) Red of wavelength 665 nm
|
Answer: (C)
| ||||
8.
|
A body of mass 4 kg is accelerated upon by a constant force, travels a distance of 5 m in the first second and a distance of 2 m in the third second. The force acting on the body is
(A) 2 N
(B) 4 N
(C) 6N
(D) 8N
|
Answer: (C)
| ||||
9.
|
A body weighs 50 grams in air and 40 grams in water. How much would it weigh in a liquid of specific gravity 1.5?
(A) 30 grams
(B) 35 grams
(C) 65 grams
(D) 45 grams
|
Answer: (B)
| ||||
10.
|
A capacitor and an inductance coil are connected in separate AC circuits with a bulb glowing in both the circuits. The bulb glows more brightly when ______.
(A) separation between the plates of the capacitor is increased.
(B) a dielectric is introduced into the gap between the plates of the capacitor.
(C) an iron rod is introduced into the inductance coil.
(D) the number of turns in the inductance coil is increased.
|
Answer: (B)
| ||||
11.
|
A bar magnet is equivalent to _______.
(A) solenoid carrying current (B) circular coil carrying current (C) toroid carrying current (D) straight conductor carrying current |
Answer: (A)
| ||||
12.
|
A beam of light of wavelength 600 nm from a distant source falls on a single slit 1mm wide and the resulting diffraction pattern is observed on a screen 2m away. The distance between the first dark fringes on either side of the central bright fringe is _______.
(A) 1.2 mm (B) 1.2 cm (C) 2.4 cm (D) 2.4 mm |
Answer: (D)
| ||||
13.
|
A beam of parallel rays is brought to a focus by a plano-convex lens. A thin concave lens of the same focal length is joined to the first lens. The effect of this is _______.
(A) the focal point shifts away from the lens by a small distance. (B) the focus remains undisturbed. T (C) the focus shifts to infinity. (D) the focal point shifts towards the lens by a small distance. |
Answer: (C)
| ||||
14.
|
A biconvex lens has a radius of curvature of magnitude 20 cm. Which one of the following options describe best the image formed of an object of height 2 cm placed 30 cm from the lens?
(A) Real, inverted, height = 1 cm (B) Virtual, upright, height = 1 cm (C) Virtual, upright, height = 0.5 cm (D) Real, inverted, height = 4 cm |
Answer: (D)
| ||||
15.
|
A body of mass 5 kg is thrown vertically up with a kinetic energy of 490 J. The height at which the kinetic energy of the body becomes half of the original value is ______.
(A) 12.5 m (B) 10 m (C) 2.5 m (D) 5 m |
Answer: (D)
| ||||
1.
|
A ray of light enters from a rarer to a denser medium. The angle of incidence is i. Then the reflected and refracted rays are mutually perpendicular to each other. The critical angle for the pair of media is
(A) Sin-1(Tan i)
(B) Tan-1(Sin i)
(C) Sin-1(Cot i)
(D) Cos-1(Tan i)
|
Answer: (C)
| ||||
2.
|
A simple pendulum is suspended from the ceiling of a lift. When the lift is at rest its time period is T. With what acceleration should the lift be accelerated upwards in order to reduce its period to T /2? (g is acceleration due to gravity).
(A) 2g
(B) 3g
(C) 4g
(D) g
|
Answer: (B)
| ||||
4.
|
A string vibrates with a frequency of 200 Hz. When its length is doubled and tension is altered, it begins to vibrate with a frequency of 300 Hz. The ratio of the new tension to the original tension is
(A) 9 : 1
(B) 1 : 9
(C) 3 : 1
(D) 1 : 3
|
Answer: (A)
| ||||
5.
|
A train is moving slowly on a straight track with a constant speed of 2 ms-1. A passenger in that train starts walking at a steady speed of 2 ms-1 to the bank of the train in the opposite direction of the motion of the train. So to an observer standing on the platform directly in front of that passenger, the velocity of the passenger appears to be _____ .
(A) 2 ms-1 in the opposite direction of the train
(B) zero
(C) 4 ms-1
(D) 2 ms-1
|
Answer: (B)
| ||||
7.
|
According to Einstein's photoelectric equation, the graph of K.E. of the photoelectron emitted from the metal versus the frequency of the incident radiation gives a straight line graph, whose slope ______.
(A) is same for all metals and independent of the intensity of the incident radiation.
(B) depends on the nature of the metal.
(C) depends on the intensity of the incident radiation.
(D) depends on the nature of the metal and also on the intensity of incident radiation.
|
Answer: (A)
| ||||
8.
|
An astronaut on a strange planet finds that acceleration due to gravity is twice as that on the surface of Earth. Which of the following could explain this?
(A) Both the mass and radius of the planet are twice as that of Earth.
(B) Mass of the planet is half as that of Earth, but radius is same as that of Earth.
(C) Both the mass and radius of the planet are half as that of Earth.
(D) Radius of the planet is half as that of Earth, but the mass is the same as that of Earth.
|
Answer: (C)
| ||||
2.
|
Two similar circular loops carry equal currents in the same direction. Un moving the coils further apart, the electric current will
(A) increase in both
(B) decrease in both
(C) remain unaltered
(D) increases in one and decreases in the second
|
Answer: (A)
|
Two tangent galvanometers A and B are identical except in their number of turns. They are connected in series. On passing a current through them, deflections of 600 and 300 are produced. The ratio of the number of turns in A and B is
(A) 1 : 3
(B) 3 : 1
(C) 1 : 2
(D) 2 : 1
|
Answer: (B)
| |
6.
|
Water is in streamline flow along a horizontal pipe with nonuniform cross-section. At a point in the pipe where the area of cross-section is 10 cm2, the velocity of water is 1 ms-1 and the pressure is 2000 Pa. The pressure at another point where the cross-sectional area is 5 cm2 is ______.
(A) 1000 Pa
(B) 500 Pa
(C) 4000 Pa
(D) 2000 Pa
|
Answer: (B)
|
7.
|
What is the minimum thickness of a thin film required for constructive interference in the reflected light from it?
Given, the refractive index of the film = 1.5, wavelength of the light incident on the film = 600 nm.
(A) 50 nm
(B) 200 nm
(C) 100 nm
(D) 300 nm
|
Answer: (C)
|
8.
|
When a neutron is disintegrated to give a b-particle, ______.
(A) a proton alone is emitted.
(B) a proton and an antineutrino are emitted.
(C) a neutrino alone is emitted.
(D) a proton and neutrino are emitted.
|
Answer: (B)
|
10.
|
Which of the following is a dichroic crystal?
(A) Quartz
(B) Tourmaline
(C) Mica
(D) Selenite
|
Answer: (B)
|
- Art, religion and science do not necessarily contradict one another because
- all three have different and mutually exclusive domains
- the only rational course is to choose science and reject religion and art
- the only rational course is to choose science and art and reject religion
- if you choose science, you should reject religion and art
- if you choose religion you should reject science
- the three can legitimately work to complement and enrich one another
- if you choose art you should reject science
- if you choose art you should reject religion
- A frame-work that is used to synthesize a collection of hypotheses and related information is called a
- hypothesis
- fact
- theory
- law
- principle
- science
- all of the above
- none of the above
- Being knowledgeable about science, the arts, and religion, makes a person
- very confused
- truly educated
- very arrogant
- very intelligent
- all of the above
- none of the above
- A scientific hypothesis is
- a theory
- a hypothesis
- a frame-work
- a law
- a principle
- an educated guess
- a fact
- The difference between science and technology is that technology deals more with
- space aliens
- development of scientific theories to address human needs
- establishment of scientific institutions to address human needs
- discovery of scientific laws to address human needs
- application of scientific principles to address human needs
- destruction of opposing scientific theories
- leprechauns
- An object falls out of an airplane, and falls freely downward. Its
- mass increases
- acceleration increases
- velocity increases
- gravity increases
- mass decreases
- velocity decreases
- acceleration decreases
- You brake suddenly. The passengers in your car lurch forward. This demonstrates
- gravity
- mass
- weight
- length
- good driving
- inertia
- that a leprechaun was crossing the road
- A truck is travelling at 10 m/s. A package drops off the truck. Neglecting air resistance, as the package hits the ground, its horizontal speed is
- 0 m/s
- 10 m/s
- 20 m/s
- depends on the height of the truck
- depends on the weight of the package
- depends on the color of the package
- 100 m/s
- A truck is decelerating. A package is dropped from the midpoint of the ceiling of the truck's storage compartment. The package hits the floor
- immediately beneath the midpoint of the ceiling
- closer to the back of the truck than the midpoint
- closer to the front of the truck than the midpoint
- all of the above
- none of the above
- You tie a rock to a string and whirl it in a horizontal circle. The string breaks. In the absence of gravity, the rock
- travels in a circle
- falls in a straight line down to the earth
- flies in a straight line vertically up into the air
- travels in a straight line horizontally away from you
- falls in a parabola to the earth
- immediately stops moving
- explodes
- A freely falling object started from rest. 2 seconds later, its speed is about
- 5 m/s
- 10 m/s
- 15 m/s
- 20 m/s
- 25 m/s
- 30 m/s
- 35 m/s
- A base ball is hit straight up into the air at a speed of 20 m/s. How long does it take to reach the high-point in its trajectory.
- 1/2 seconds
- 1 second
- 2 seconds
- 4 seconds
- 5 seconds
- 10 seconds
- 20 seconds
- Galileo used inclined planes to ____ the effective acceleration (of a rolling cylinder or ball) compared to earth's gravity
- increase
- stop
- decrease
- keep the same
- none of the above
- all of the above
- A baseball is hit vertically upward at 30 m/s. One second later its speed is about ____ vertically upward.
- 30 m/s
- 35 m/s
- 40 m/s
- 25 m/s
- 20 m/s
- 15 m/s
- 10 m/s
- 0 m/s
- A ball is thrown upwards and caught once it comes back down. The speed of the ball as it returns and is caught is ___ if there is air resistance compared to if there were no air resistance.
- greater
- the same
- double
- zero
- infinite
- lower
- none of the above
- The force of gravity acting on a 100 kg person is ___ compared to the force of gravity on a 1 kg book
- 4 times larger
- the same
- double
- zero
- 10 times larger
- 100 times larger
- lower
- none of the above
- There is only one force acting on an object. For the object to travel at constant velocity, this force must be
- a constant non-zero value
- a varying non-zero value
- a constant zero value
- a positive value
- a negative value
- none of the above
- An object's mass is increasing while its acceleration is constant. The force applied to the object must
- be increasing
- be decreasing
- stay the same
- increase and then decrease
- decrease and then increase
- none of the above
- An object is moving in a circle with constant speed. The object has
- a constant velocity
- zero acceleration
- a constant acceleration
- zero velocity
- no forces acting on it
- no net force acting on
- changing velocity but constant acceleration
- changing velocity and acceleration
- A man weighs 900 N, and is standing with his feet across three bathroom scales so his weight is equally shared among the three scales. The reading on each scale is
- 900 N
- 2700 N
- 300 N
- 90 N
- 30 N
- none of the above
- A pebble flies up and hits the windshield of a truck travelling at 80 km/hr. The force of the impact is
- greater on the pebble
- lesser on the pebble
- greater on the pebble than on the windshield, if the pebble shatters
- greater on the windshield than on the pebble, if the windshield shatters
- the same on pebble and on the windshield
- none of the above
- As a meteor falls towards earth, it is attracted by earth's gravity. What is the reaction to this force?
- air resistance
- the meteor's inertia
- the earth's inertia
- the earth's gravity
- earth is attracted by the meteor's gravity
- the meteor is attracted by all the particles in the universe
- earth is attracted by all the particles in the universe
- A person who has a mass of 100 kg is attracted to the earth by a force of about 1000 N. The force with which this person attracts the earth is
- zero
- much smaller
- 10 N
- 100 N
- 500 N
- 1000 N
- 2000 N
- none of the above
- Two people are in a tug-of-war. Each person pulls the rope with a force of 500 N. What is the tension in the rope?
- 1000 N
- zero
- 250 N
- 500 N
- depends on the diameter of the rope
- none of the above
- Every force has an equal and opposite reaction. A force and its reaction
- cancel each other
- are two interactions
- are parts of a single interaction
- have double the effect compared to a force without its reaction
- none of the above
- A 7-year old child and a 21-year old college student pull as hard as they can on opposite ends of a rope in a tug-of war. The force is applied to the rope by the child is ___ compared to the force applied by the college student.
- smaller
- the same
- larger
- depends on how strong the child is
- none of the above
- A railroad car that is initially at rest is hit by an identical railroad car traveling with a momentum of 100 units. The cars stick together and move down the railroad tracks. The combined momentum of the cars after the collision is
- 200 units
- 100 units
- 50 units
- 0 units
- none of the above
- An athlete performs a high jump. As she lands, she bends her knees as she reaches the ground. This increases the time of impact. The result is to ___ the force that her body experiences.
- increase
- keep the same
- reduce
- the answer depends on how high she jumped
- none of the above
- A canon ball travelling at 10 m/s has a momentum of 50 kg m/s. What is the mass of the ball?
- 10 kg
- 50 kg
- 20 kg
- 5 kg
- 25 kg
- none of the above
- A car travelling at 10 km/hr runs into a haystack and comes to a stop. This is less dangerous than if the car had driven into a concrete wall. This is because driving into the haystack results in
- reduced impulse
- increased impulse
- the same impulse
- reduced change in momentum
- increased change in momentum
- the same change in momentum
- increased time of impact and reduced impact force
- increased time of impact and increased impact force
- reduced time of impact and reduced impact force
- reduced time of impact and increased impact force
- You accelerate. The speed of your car doubles. Which of the following items quadruples as a result?
- momentum
- potential energy
- acceleration
- kinetic energy
- all of these
- none of these
- Two railroad cars move towards each other at 10 m/s. They collide and bounce backward at 20 m/s. This event violates conservation of
- mass
- acceleration
- kinetic energy
- potential energy
- collisions
- none of these
- all of these
- A certain car has momentum. It therefore must also have
- acceleration
- kinetic energy
- force
- potential energy
- impulse
- none of these
- all of these
- A 100 Newton force is used to push a table by 5 meters. The amount of work done on the table is
- 5 J
- 100 J
- 0 J
- 500 J
- 1000 J
- A meteor moving at 30 m/s collides with a twice-as-massive meteor and sticks to it. After the collision, the combined meteors have a kinetic energy that is ___ as much as the total kinetic energy before the collision.
- the same
- twice
- one third
- three quarters
- two thirds
- not enough information
- A farmer replaces the tires on his tractor with smaller diameter tires. For a given RPM, the linear speed of the tractor is now
- the same as before
- more
- less
- all of the above
- none of the above
- not enough information
- Based on rotational inertia, which will take longer to roll down an incline… a can filled with ice, or the same can filled with water?
- ice
- water
- both the same
- depends on the size of the can
- depends on the temperature of the water
- not enough information
- If you kick a football so that the force of your kick passes through its center of gravity. As it flies through the air, the football will
- not move
- rotate clockwise
- rotate counter-clockwise
- rotate from left to right
- not rotate
- not enough information
- As you slow down your car, the rotational speed of your tires is halved. The linear speed of a bug sitting at the edge of your tire will
- double
- quadruple
- stay the same
- be halved
- be reduced to a quarter
- During an ice age, the polar ice caps grow in size and the water-level drops in the oceans all around the earth. This redistribution of mass will cause the earth's day to become
- longer
- shorter
- stay the same
- the earth will stop rotating
- not enough information
- If the mass of the sun and the earth are both tripled, and the distance between them is also tripled, the force between them will be
- doubled
- halved
- tripled
- one third
- the same
- nine times
- one ninth
- You don’t see tides in your swimming pool. This is because
- your contact lenses are missing
- magnetic forces hold the water down
- the pool is too shallow for tides
- the pool is too deep for tides
- the tides happen at night when you are asleep
- all parts of the pool are at about the same distance to the moon
- The distance between the earth and the moon is reduced to one third. The gravitational force between them becomes
- 3 times bigger
- 3 times smaller
- 9 times bigger
- 9 times smaller
- stays the same
- What keeps the earth from falling into the sun?
- strings hold the earth up
- gravity holds the earth up
- the earth's tangential speed
- smoke and mirrors
- the sun's gravity is zero where the earth is
- What is a black hole ?
- a hole in your dry-wall
- space with no stars
- space with no light
- space with no mass
- a space with mass so highly concentrated that even light cant escape the resulting gravity
- A ball is thrown horizontally. After it has left the thrower's hand, what is the acceleration that it experiences ?
- an acceleration of - 1 g horizontally
- an acceleration of + 1 g horizontally
- 1 g downward
- 1 g upward
- no acceleration
- A pitcher drops a ball. At the same instant, another ball is thrown at an angle of 5 degrees below the horizontal. Which ball will hit the ground first ?
- the dropped ball
- the thrown ball
- both reach at the same time
- the dropped ball turns into a banana and flies away
- A meteor is captured by earth's gravitational field and goes into elliptical orbit around the earth. Compared to when the meteor is far from the earth, its speed when it is close to the earth is
- the same
- faster
- slower
- not enough information
- depends on whether today is Tuesday or Thursday
- A student throws a ball horizontally from the top of a 20 meter tall building. The ball hits the ground 20 m from the building. What was the students pitching speed?
- 20 m/s
- 1 m/s
- 5 m/s
- 10 m/s
- not enough information
- What keeps the moon from falling?
- earth's gravity is zero near the moon
- earth's gravity is balanced by the sun's gravity
- strings, smoke and mirrors
- magnetic forces
- electrical forces
- the moon is falling around the earth
- Why are the atoms in a baby's body about the same age as the atoms in an adult's body? Because…
- Inside every baby is an adult
- Inside every adult is a baby
- Atoms are eternal, i.e., they always existed
- All atoms and elements were formed at the Big Bang, about 14 billion years ago
- Atoms, that are present in both baby and adult, were formed about the same time by exploding stars
- Most of the mass of an atom is in its
- electrons
- massons
- atomic mass units
- protons and neutrons
- miceons
- The atoms in your body are mostly empty space, and so are the atoms in any wall. Why then is your body unable to pass through walls ? Because of…
- absence of doors in the walls
- magnetic forces between atoms
- nuclear forces
- gravitational forces
- electrical forces
- atomic vibrations
- Which of the following is a mixture?
- water
- carbon-dioxide
- methane
- air
- salt
- sugar
- none of the above
- all of the above
- When sodium and chlorine react to form salt, a certain amount of energy is given off. This energy is ___ compared to the energy it takes to separate sodium and chlorine to form salt.
- less
- more
- the same
- it is impossible to separate sodium and chlorine from salt
- Which has more surface area?
- a whole potato
- a potato cut into four quarters
- a potato cut into Freedom fries (ex-French fries)
- all of these have the same surface area
- Doubling the length of the sides of a cube multiplies its volume by
- 2 and its surface area by 1
- 4 and its surface area by 2
- 6 and its surface area by 3
- 8 and its surface area by 4
- does not change its volume
- Halving the diameter of a rope will multiply its strength by
- 1
- 1/2
- 1/4
- 1/8
- 2
- 4
- not enough information
- Which has greater surface area for a given body weight (i.e., greater surface area per unit weight)
- a snake
- an elephant
- a bowling ball
- a piece of string
- not enough information
- An object has a mass of 60 kg and a density of 30 kg per cubic meter. What is the volume of the object?
- 1800 cubic meters
- 2 cubic meters
- 30 cubic meters
- 60 cubic meters
- not enough information
- You submerge a gallon jug in your swimming pool. Where is the water pressure the greatest?
- left side of the jug
- right side of the jug
- top of the jug
- middle of the jug
- bottom of the jug
- all of the above
- none of the above
- You have a sheet of rolled out dough. You roll this up into a ball. Doing this reduces its
- mass
- momentum
- volume
- surface area
- all of the above
- none of the above
- Fill the compartments of an ice-cube tray half full with iron nails. Top off with water and freeze. Now drop one of these ice cubes in a glass of water. As it melts, the water level in the glass will
- drop
- rise
- stay the same
- all of the above
- An iceberg is partly immersed, as it floats in the ocean. It is buoyed up by
- leprechauns
- the gravitational attraction from the moon
- a force equal to the weight of the iceberg
- a force less than the weight of the iceberg
- a force greater than the weight of the iceberg
- a force equal to twice the weight of the water that is displaced
- all of the above
- none of the above
- The buoyant force is the smallest on a completely immersed
- 2 cubic centimeter block of iron
- 2 cubic centimeter block of aluminum
- 2 cubic centimeter block of wood
- the force is the same on all three blocks
- none of the above
- not enough info
- A Helium filled balloon is released and rises up into the sky. As it moves upward, it
- becomes heavier
- becomes smaller
- becomes bigger
- stays the same size
- not enough information
- A metal gas can will float up into the air if you fill it with
- sand
- water
- air
- helium
- nitrogen
- all of the above
- none of the above
- A pair of Magdeburg hemispheres are placed in contact and then evacuated. In which of the following situations would it take the most force to pull them apart
- out in space
- at the top of the earth's atmosphere
- at sea level
- 1 km beneath the ocean surface
- 5 km below the ocean surface
- A balloon filled with air is tied to a diver's helmet with a 1 foot long string. As the diver dives to the bottom of a deep lake, the balloon
- expands
- contracts
- expands and then contracts
- contracts and then expands
- alternates between expansion and contraction
- stays the same volume
- all of the above
- As a steady wind rushes over a pointed roof, the pressure above the roof is
- higher
- lower
- the same
- alternates between higher and lower
- all of the above
- If you were to measure out a plot of land on a very cold day the resulting plot would be ___ if you used a cloth tape-measure compared to a steel tape-measure.
- larger
- smaller
- the same
- none of the above
- all of the above
- To reduce the odds of your radiator coolant freezing in the winter, let's say that you add a chemical that changes the specific-heat of the coolant. You want the specific heat to
- increase
- decrease
- stay the same
- none of the above
- all of the above
- You hide your gold ring in your freezer. As the ring drops in temperature, the hole inside the ring becomes
- larger
- smaller
- stays the same
- none of the above
- all of the above
- The boiling point of water is 100 degrees C. What would this be on a Kelvin scale?
- 100 K
- 73 K
- 173 K
- 273 K
- 373 K
- 473 K
- 573 K
- You fill a glass bottle with water and put it in your freezer. The next morning you find that the bottle has shattered. This is because
- the bottle expanded
- the bottle contracted
- the water expanded when it froze in the bottle
- the water contracted when it froze in the bottle
- leprechauns in the freezer
- space aliens from mars
- Copper and aluminum have outer electrons that are loosely bound to the atoms. This makes these elements
- poor electrical conductors
- expensive
- pure
- slippery
- good electrical conductors
- all of the above
- none of the above
- Radiation from the star "Betelgeuse" is of longer wavelength than the sun. This means that the sun is ___ compared to that star.
- cooler
- hotter
- at the same temperature
- larger
- smaller
- bluer
- At the same temperature, molecules of hydrogen have ___ speed compared to molecules of oxygen.
- higher
- lower
- the same
- no
- infinite
- At 350 degrees C, your oven radiates with a wavelength that is ___ compared to your stove top that is 500 C.
- shorter
- longer
- the same
- none of the above
- all of the above
- To reduce the odds of being burned, would you choose to walk rapidly across a bed of red hot
- coal
- iron
- gold
- aluminum
- all of the above
- When water freezes it
- absorbs energy
- gives off energy
- neither
- both
- You wet your finger before you briefly touch a clothes iron. The protection (from wetting your finger) would be higher if the "heat of vaporization" of the water is
- higher
- lower
- the same
- zero
- all of the above
- When a metal is heated until it vaporizes, it
- absorbs energy
- gives off energy
- neither
- both
- As your neighborhood pond is in the process of freezing over, it ___ the surrounding air.
- cools
- warms
- neither cools nor warms
- both warms and cools
- Water at 0 degrees C will warm up faster than ice at 0 degrees C, because
- water is more liquid
- ice is more solid
- ice absorbs heat when it melts
- ice gives out heat when it melts
- water likes ice
- there is no ice at the earth's equator
- The pitch (frequency) of a car's horn ___ as the car drives past you.
- rises
- drops
- stays the same
- all of the above
- none of the above
- The frequency of a pendulum on a high-gravity planet is ____ compared to the frequency on a low-gravity planet.
- higher
- lower
- the same
- all of the above
- none of the above
- A buoy rises and falls by a total height of 2 meters on the open ocean. What is the amplitude of the waves.
- 2 meters
- 4 meters
- 1 meter
- 0.5 meters
- 8 meters
- all of the above
- A star is moving towards our solar system. Based on the Doppler effect, the frequency of its light is shifted towards
- blue
- red
- white
- black
- all of the above
- For two waves to be in phase, a sufficient condition is that the waves have the same
- amplitude
- wavelength
- frequency
- speed
- instants in time at which the wave amplitude is zero
- Compressions and rarefactions are not present with
- longitudinal waves
- transverse waves
- both of these
- neither of these
- not enough information provided
- none of the above
- all of the above
- All other things being equal, the speed of a sound wave ____ if its wavelength increases.
- increases
- decreases
- both of these
- neither of these
- not enough information provided
- none of the above
- all of the above
- A 680-hertz wave with a wavelength of 1/2 meter travels in air with a speed of
- 680 m/s
- 6800 m/s
- 340 m/s
- 3400 m/s
- 1/2 m/s
- 1 m/s
- You hear a lot of static from your radio. Is the static you hear more likely to result from receiving FM or AM radio waves?
- FM
- AM
- Neither produces any static.
- Both produce equal amounts of static.
- not enough information provided
- none of the above
- all of the above
- You see lightning flash in the distance, and hear the thunder 10 seconds later. Assuming that sound travels at 340 m/s through the air, how far away was the lightning strike?
- 34 meters
- 3.4 meters
- 340 meters
- 3.4 km
- 34 km
- 340 km
- Two charges are separated by a distance of 1 meter, and experience a mutual repulsive force of 1 Newton. If the distance between the charges is changed to 2 meters, what is the resulting repulsive force?
- 1 N
- 2 N
- 4 N
- 8 N
- 1/2 N
- 1/4 N
- 1/8 N
- What does a lightning rod do?
- Attracts lightning to your building
- Repels lightning from your building
- Collects electrons from your building
- Collects protons from your building
- Reduces charge buildup on your building
- not enough information provided
- none of the above
- all of the above
- Two charged particles are held at a certain distance from each other. When they are released, they move and the force on each particle decreases. The particles MUST both be
- positive
- negative
- of the same sign
- of opposite sign
- not enough information provided
- none of the above
- all of the above
- If the electrical potential of a single electron is 1-volt in an electrical field, what is the electrical potential of 10 electrons at the same spot in the field?
- 10 volts
- 100 volts
- 1000 volts
- 1 volt
- 1/10 volts
- 1/100 volts
- A pith ball is suspended by a non-conducting fiber. When a positively charged rod is brought near the ball, but without touching it, the ball
- becomes positively charged
- becomes negatively charged
- becomes lighter
- becomes heavier
- becomes depolarized
- becomes polarized
- What is the source of the electrons that heat up your clothes iron
- a hydroelectric dam
- a coal power plant
- the power outlet in your home
- a nuclear power plant
- radioactivity in your clothes-iron
- the moon shining on your clothes-iron
- atoms in the filament of your clothes-iron
- You buy a hair-dryer in another country and it is rated at 220 V. If you plug it into a 110 V outlet, the current in the dryer is ___ compared to if you plug it into a 220 V outlet.
- the same
- two times greater
- four times greater
- 110 times greater
- half
- a quarter
- Three light-bulbs are connected in parallel across a battery. One has a thick filament, one a thin filament, and one a medium filament. Which one has the lowest voltage across the lamp.
- Medium filament
- thin filament
- thick filament
- there is no voltage across the filaments
- voltage is the same across all three filaments
- A light bulb is connected to a 200 V power source. A current of 2.0 Amps flows across the bulb. How much power is being dissipated by the bulb?
- 200 W
- 400 W
- 100 W
- 50 W
- 800 W
- none of the above
- A voltage of 30 V is applied across a 30 ohm resistor. What is the current flowing through the resistor.
- 0 Amps
- 1 Amp
- 2 Amps
- 900 Amps
- 300 Amps
- 30 Amps
- A magnetic field runs from the top of this page down to the bottom of this page. An electron is fired from left to right across the page. The electron is ___ by the magnetic field.
- Indifferent to
- attracted by
- repelled by
- attracted then repelled by
- deflected out of the plane of the page
- made to move in square patterns
- A small piece of metal is attracted to a large magnet. The magnet is attracted to the small piece of metal with a force that is ____ compared to the force with which the metal is attracted to the magnet.
- zero
- infinite
- very large
- very small
- the same
- similar but not the same
- A proton is travelling almost but not quite parallel to a magnetic field. An electron is travelling perpendicular to the same magnetic field. The force on the electron is ____ compared to the force on the proton.
- zero
- infinite
- large
- small
- the same
- similar but not the same
- Magnetism is caused by
- magnetons
- magneticians
- pieces of iron
- pieces of gold
- pieces of copper
- moving magnetic charges
- moving electric charges
- Some of the planets in our Solar system have magnetic fields. The likely cause of these magnetic fields is
- a reflection of the Sun's magnetic field
- magnetons
- magneticians
- moving magnetic charges in the core of the planets
- moving magnetic charges in the atmosphere of the planets
- moving electric charges in the core of the planets
- pieces of iron on the planets
- pieces of gold on the planets
- pieces of copper on the planets
- Blue light has ___ wavelength compared to Red light.
- the same
- longer
- zero
- infinite
- shorter
- none of the above
- Earth's atmosphere lets in most
- infrared light
- ultraviolet light
- visible light
- of any kind of radiation
- none of the above
- all of the above
- Which of these waves have the longest wavelength?
- infrared light
- ultraviolet light
- red light
- blue light
- X-rays
- yellow light
- radio waves
- An electromagnetic wave has a wavelength of 1 m. What is its frequency?
- 1 Hertz
- 3 Hz
- 300 Hz
- 3000 Hz
- 30,000 Hz
- 300,000 Hz
- 3,000,000 Hz
- 300,000,000 Hz
- If Proxima Centauri, our closest star, were to explode right now, it would take about 4 years for us to know about it because
- it takes 4 years to build a big telescope to see the star
- it takes 4 years to obtain funding to build the necessary telescope
- the star is 4 years old
- it takes 4 years for the light from this star to reach us
- it takes 4 years for a signal from us to reach the star
- it takes 4 years for us to travel by space-ship to the star
- The colors on your computer monitor arise by color
- mixing
- multiplication
- addition
- division
- subtraction
- exponentiation
- Sunsets can appear reddish due to
- reflection from red smog in the air
- reflection from blue smog in the air
- reflection from red dust particles in the air
- reflection from blue dust particles in the air
- blue light being scattered away by small particles in the air
- red light being scattered away by large particles
- Clothes of a certain color can appear black in a room that is lit by a light that is
- the same color as the clothes
- the complementary color of the clothes
- red in color
- blue in color
- white in color
- the supplementary color of the clothes
- Which will take longer to warm up in the summer sunlight
- a white house
- a black house
- a brown house
- a pink house
- The sky is the clearest and deepest blue when there are ____ dust particles in the air
- many
- very few
- very many
- infinite numbers of
- large sized
- medium sized
- Double the amplitude of a wave and you necessarily change its
- wavelength
- frequency
- speed
- color
- taste
- none of the above
- all of the above
- Charge carriers in a metal are not protons because protons are
- neutral
- positively charged
- negatively charged
- introverts
- not very socially inclined
- tightly bound
- Connect three light-bulbs in parallel with a battery and you draw a certain amount of current. Connect the three light-bulbs in series with the same battery and you draw ____ current.
- the same
- more
- less
- zero
- infinite
- none of the above
- all of the above
- A steady magnetic field runs from top to bottom of this page. An electron is moving from bottom to top of this page. The force on the electron, exerted by the magnetic field, is
- in the same direction as the electron's motion
- in the opposite direction as the electron's motion
- from left to right on this page
- from right to left on this page
- perpendicular to the plan of this page
- zero
- infinite
- none of the above
- A proton vibrates from side-to-side 10 times a second. It generates an electromagnetic field with a frequency of
- 1 Hz
- 2 Hz
- 10 Hz
- 100 Hz
- 10 meters
- 100 meters
- 10 meters/second
- 100 meters/second
- To most efficiently absorb an electromagnetic wave, the frequency of the wave should be ___ the natural frequency of the material being used to absorb the wave.
- greater than
- less than
- equal to
- zero compared to
- infinite compared to
- none of the above
- all of the above
- When electron clouds in a material are made to oscillate ____ waves are necessarily emitted
- electronic
- magnetic
- de Broglie
- electromagnetic
- sound
- ocean
- ultraviolet
- A surface that appears smooth to one kind of waves can appear rough to another kind of waves whose wavelength is ____ compared to the first kind.
- zero
- infinite
- smaller
- larger
- the same
- all of the above
- none of the above
- The bottom of a swimming pool appears closer to the surface than it actually is. This is caused by ___ of light.
- refraction
- fraction
- reflection
- flection
- absorption
- sorption
- denaturization
- About 9 AM, in the morning, a beam of sunlight enters the water of your swimming pool. The beam necessarily bends ___ as it enters the water.
- by zero degrees
- by 180 degrees
- by 90 degrees
- towards the normal
- away from the normal
- none of the above
- all of the above
- Can longitudinal waves experience polarization?
- No
- yes
- sometimes
- Depends on the speed of the wave
- depends on the frequency of the wave
- depends on the amplitude of the wave
- none of the above
- all of the above
- When the axes of two polaroid filters are perpendicular to each other ___ of the incoming light can pass through the combined filters
- all
- none
- half
- red frequencies
- blue frequencies
- white frequencies
- slower photons
- faster photons
- An example of interefernce is
- a mirage
- light bending when it enters water
- light bending when it exits water
- red sunset
- orange harvest moon
- rainbow in the sky
- rainbow colors in gasoline on water
- If destructive interference eliminates red from white light, what color is the remaining light likely to be ?
- red
- brown
- black
- white
- cyan
- purple
- yellow
- Laser light is
- incoherent
- coherent
- polychromatic
- inchromatic
- out of phase
- sometimes in phase, sometimes out of phase
- always red
- An non-excited atom absorbs a single red photon, and then emits another photon. The emitted photon can be
- blue
- ultraviolet
- violet
- green
- white
- infrared
- A material is heated so it is "red-hot". The atoms in the material are
- not vibrating
- vibrating at an infinite range of frequencies
- vibrating at about the same frequency
- oscillating in figures of eight
- oscillating in circles
- oscillating in squares
- What is the primary source of the electromagnetic radiation that is continually emitted by your body?
- your magnetic personality
- your charm bracelet
- radioactive atoms in your bones
- your body temperature vibrates your atoms
- your body clock
- your most recent meal
- Which of the following entities is most prone to being impacted by quantum effects
- a whale
- a horse
- a meteor
- a meteorite
- an egg
- an electron
- a baseball
- An ultraviolet laser beam and an infrared laser beam have the same number of photons. Which beam has the lower energy?
- ultraviolet
- infrared
- both have the same energy
- neither has any energy
- depends on the speed of the ultraviolet light
- depends on the frequency of the infrared light
- all of the above
- A photon's energy is given by its frequency multipled by ___ constant
- Henry's
- Jame's
- Newton's
- Einstein's
- Planck's
- phonton's
- energy
- The following entites are all moving at the same speed. Based on quantum physics, which of these entities has the shortest wavelength?
- an elephant
- a space-ship
- an astronaut
- a mouse
- an insect
- the earth
- an electron
- a proton
- Light from an incandescent light bulb (e.g., in a table lamp) is
- monochromatic
- coherent
- in phase
- all of these
- none of these
- An atom absorbs a photon with 5 units of energy. It then emits a photon with an energy that can be
- 10 units
- 8 units
- 7 units
- 5 to 6 units
- 5 or less units
- 10 to 20 units
- 20 units
- A bar of iron is heated until it is "red hot". This means that
- All of the energy of the bar is being radiated as heat
- All of the energy of the bar is being radiated as infrared waves
- its molecules are vibrating at an infinite range of rates
- its molecules are vibrating at a wide (but not infinite) range of rates
- its molecules are vibrating at nearly identical rates
- its molecules are not vibrating because they are fixed in place
- its molecules are not vibrating because only the electrons can vibrate
- Which of the following is not emitting electromagnetic radiation
- A radio transmitter antenna
- A TV transmitter antenna
- A red hot piece of iron
- Molten lead
- The surface of the sun
- An ice cube
- All of these
- None of these
- Quantum uncertainty has the greatest effect on
- a car
- a human
- an atom
- an electron
- an elephant
- a whale
- a molecule
- A beam of yellow light and a beam of ultraviolet light have the same total energy. Which has fewer photons ?
- yellow beam
- ultraviolet beam
- both have the same number of photons
- neither has any photons
- it is impossible for a yellow beam and an ultraviolet beam to have the same total energy
- there is no such thing as energy
- A photon's energy divided by its frequency
- is higher if the photon's energy is higher
- is lower if the photon's energy is lower
- is higher if the photon's frequency is higher
- is higher if the photon's frequency is lower
- is a constant called the photon constant
- is a constant called Planck's constant
- is a constant called the gravitational constant
- is a constant called Maxwell's constant
- An elephant and a mouse are moving at the same speed. Which has the smaller wavelength?
- Neither has a wavelength
- Both have the same wavelength
- If they have the same interests, then they are on the same wavelength
- Depends on if they are travelling in the same direction or in different directions
- The elephant
- The mouse
- The kangaroo
- Double the amplitude of a wave and you necessarily change its
- wavelength
- frequency
- speed
- color
- taste
- none of the above
- all of the above
- Charge carriers in a metal are not protons because protons are
- neutral
- positively charged
- negatively charged
- introverts
- not very socially inclined
- tightly bound
- Connect three light-bulbs in parallel with a battery and you draw a certain amount of current. Connect the three light-bulbs in series with the same battery and you draw ____ current.
- the same
- more
- less
- zero
- infinite
- none of the above
- all of the above
- A steady magnetic field runs from top to bottom of this page. An electron is moving from bottom to top of this page. The force on the electron, exerted by the magnetic field, is
- in the same direction as the electron's motion
- in the opposite direction as the electron's motion
- from left to right on this page
- from right to left on this page
- perpendicular to the plan of this page
- zero
- infinite
- none of the above
- A proton vibrates from side-to-side 10 times a second. It generates an electromagnetic field with a frequency of
- 1 Hz
- 2 Hz
- 10 Hz
- 100 Hz
- 10 meters
- 100 meters
- 10 meters/second
- 100 meters/second
- To most efficiently absorb an electromagnetic wave, the frequency of the wave should be ___ the natural frequency of the material being used to absorb the wave.
- greater than
- less than
- equal to
- zero compared to
- infinite compared to
- none of the above
- all of the above
- When electron clouds in a material are made to oscillate ____ waves are necessarily emitted
- electronic
- magnetic
- de Broglie
- electromagnetic
- sound
- ocean
- ultraviolet
- A surface that appears smooth to one kind of waves can appear rough to another kind of waves whose wavelength is ____ compared to the first kind.
- zero
- infinite
- smaller
- larger
- the same
- all of the above
- none of the above
- The bottom of a swimming pool appears closer to the surface than it actually is. This is caused by ___ of light.
- refraction
- fraction
- reflection
- flection
- absorption
- sorption
- denaturization
- About 9 AM, in the morning, a beam of sunlight enters the water of your swimming pool. The beam necessarily bends ___ as it enters the water.
- by zero degrees
- by 180 degrees
- by 90 degrees
- towards the normal
- away from the normal
- none of the above
- all of the above
- Can longitudinal waves experience polarization?
- No
- yes
- sometimes
- Depends on the speed of the wave
- depends on the frequency of the wave
- depends on the amplitude of the wave
- none of the above
- all of the above
- When the axes of two polaroid filters are perpendicular to each other ___ of the incoming light can pass through the combined filters
- all
- none
- half
- red frequencies
- blue frequencies
- white frequencies
- slower photons
- faster photons
- An example of interefernce is
- a mirage
- light bending when it enters water
- light bending when it exits water
- red sunset
- orange harvest moon
- rainbow in the sky
- rainbow colors in gasoline on water
- If destructive interference eliminates red from white light, what color is the remaining light likely to be ?
- red
- brown
- black
- white
- cyan
- purple
- yellow
- Laser light is
- incoherent
- coherent
- polychromatic
- inchromatic
- out of phase
- sometimes in phase, sometimes out of phase
- always red
- An non-excited atom absorbs a single red photon, and then emits another photon. The emitted photon can be
- blue
- ultraviolet
- violet
- green
- white
- infrared
- A material is heated so it is "red-hot". The atoms in the material are
- not vibrating
- vibrating at an infinite range of frequencies
- vibrating at about the same frequency
- oscillating in figures of eight
- oscillating in circles
- oscillating in squares
- What is the primary source of the electromagnetic radiation that is continually emitted by your body?
- your magnetic personality
- your charm bracelet
- radioactive atoms in your bones
- your body temperature vibrates your atoms
- your body clock
- your most recent meal
- Which of the following entities is most prone to being impacted by quantum effects
- a whale
- a horse
- a meteor
- a meteorite
- an egg
- an electron
- a baseball
- An ultraviolet laser beam and an infrared laser beam have the same number of photons. Which beam has the lower energy?
- ultraviolet
- infrared
- both have the same energy
- neither has any energy
- depends on the speed of the ultraviolet light
- depends on the frequency of the infrared light
- all of the above
- A photon's energy is given by its frequency multipled by ___ constant
- Henry's
- Jame's
- Newton's
- Einstein's
- Planck's
- phonton's
- energy
- The following entites are all moving at the same speed. Based on quantum physics, which of these entities has the shortest wavelength?
- an elephant
- a space-ship
- an astronaut
- a mouse
- an insect
- the earth
- an electron
- a proton
- In the Bohr model, electrons can orbit the nucleus of an atom in a set of discrete rings. The perimeter of each ring corresponds to an integral number of ___ of the electron.
- de Broglie spins
- de Broglie rotations
- de Broglie frequencies
- de Broglie wavelengths
- de Broglie flavors
- de Broglie amplitudes
- Alpha particles contain
- protons
- electrons
- neutrons
- alphons
- particlons
- positrons
- gamma rays
- The Bohr model of the atom has ___ circling the atomic nucleus.
- protons
- electrons
- neutrons
- alphons
- particlons
- positrons
- gamma rays
- Your hand and your table are both mostly empty space. Despite this, your hand does not pass through the table because
- Your hand does not realize that it is mostly empty space
- Your table does not realize that it is mostly empty space
- Your table is not mostly empty space
- Your hand is not mostly empty space
- magnetic fields keep your hand from passing through the table
- electric fields keep your hand from passing through the table
- gravitational fields keep your hand from passing through the table
- We encounter radioactivity during the course of our lives. Most of this exposure comes from
- radios
- TV
- nuclear power plants
- nuclear weapons testing
- space ships
- aliens
- the natural environment
- medical and dental X-rays
- An alpha particle is absorbed by an atomic nucleus. If nothing else happens what changes in the nucleus.
- the number of protons is reduced
- the number of electrons is reduced
- the number of neutrons is reduced
- the number of protons is increased
- the number of electrons is increased
- the number of neutrons is increased
- What happens if a Lithium atom emits an alpha particle? It becomes
- a lithium isotope
- a lithium ion
- helium
- hydrogen
- beryllium
- boron
- oxygen
- A 12,000 year-old sample of old carbon is 1/4 as radioactive as a current sample of carbon. Based on this value, what is the approximate half-life of Carbon 14.
- 12,000 years
- 12,000 days
- 6,000 years
- 6,000 days
- 3,000 years
- 3,000 days
- 24,000 years
- 48,000 years
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Answer:Actually the mistake is not in the numbers.The mistake is in the 1st line.
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What is the speed of electricity ? The speed of electricity really depends on what you mean by the word "electricity". This w...
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Why Magnet Is Used In Speaker ..?? All speakers don't use magnets. Only magnetic speakers use a magnet to produce mech...
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Would a magnetic compass be suitable to be used for space travel..? No. Magnetic compasses work based on the Earth's mantic fi...
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Why 0! is equal to 1 ..?? We Know , n! = n x (n-1)! Dividing both sides by n , We get n!/n = n x (n-1)!/n Or, n!/n =...
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What's the difference between fission & fusion ? A nuclear reaction is a process in which atoms collide with other atoms ...
