Physics Questions and Answers

1.

Water has maximum density at............

   A.) 0 C
   B.) -15 C
   C.) 4 C
   D.) 15 C

Answer: Option 'C'

4 C

2.

An air bubble in water will act like a

   A.) convex lens
   B.) concave lens
   C.) convex mirror
   D.) concave mirror

Answer: Option 'B'

concave lens

3.

Quality of transmission depends upon

   A.) Nature of signal only
   B.) Nature of medium only
   C.) Both (A) and (B)
   D.) Neither A nor B

Answer: Option 'C'

Quality of transmission is governed both by nature of signal and nature of communication channel/medium.

4.

When an electric bulb breaks , there is an explosive sound. That is due to

   A.) the chemical reaction between the gases inside the bulb
   B.) the compressed gases inside rushing out suddenly
   C.) the air outside rushing in to fill the vacuum inside the bulb
   D.) None of these

Answer: Option 'C'

The inside of the bulb being a vacuum, the outside air rushes in when the bulb is broken. The vibrations of the rushing air molecules produce the sound.

5.

Quality of transmission depends upon

   A.) Nature of signal only
   B.) Nature of medium only
   C.) Both (A) and (B)
   D.) Neither A nor B

Answer: Option 'C'

Both (A) and (B)
Quality of transmission is governed both by nature of signal and nature of communication channel/medium.

6.

The image of an object formed on the retina of the eye is 

   A.) virtual and upright
   B.) virtual and inverted
   C.) real and inverted
   D.) Real and upright

Answer: Option 'C'

Although  the image is inverted the mental interpretation of the effect on the retina is as though it is erect

7.

Erg cross Sec is the unit of

   A.) Angular momentum
   B.) Linear Momentum
   C.) Planck's constant
   D.) Energy

Answer: Option 'C'

Planck's constant

8.

A bucket of water is hung from a spring balance. A piece of iron is suspended in the water without touching the sides or touching the bottom of the bucket. The reading of the spring balance

   A.) does not change
   B.) will increase
   C.) will decrease
   D.) varies with the increase of depth of the immersion of the iron piece

Answer: Option 'B'

will increase
When the piece of iron is lowered into the water, the water level in the bucket increases. And so the pressure at the bottom of bucket also increases. Thus the total thrust at the botto also increases. Therefore the spring balance reading increases.

9.

Which of the following is not a vector quantity

   A.) speed
   B.) velocity
   C.) torque
   D.) displacement

Answer: Option 'A'

speed

10.

Two electric bulbs marked 25W – 220V and 100W – 220V are connected in series to a 440Vsupply. Which of the bulbs will fuse?

   A.) 100 W
   B.) 25 W
   C.) Both
   D.) Neither

Answer: Option 'B'

Resistances of both the bulbs are

R1=V^2/P1 = 220^2/25

R2 = V^2/P2 = 220^2/100

Hence  R1gt ; R2R1gt ; R2

When connected in series, the voltages divide in them in the ratio of their resistances. The voltage of 440 V devides in such a way that voltage across 25 w bulb will be more than 220 V. Hence 25 w bulb will fuse.

11.

"Light years" is the unit of _____?

   A.) Light Intensity
   B.) Distance
   C.) Acceleration
   D.) Weight

Answer: Option 'B'

Distance

12.

A solid ball of metal has a spherical cavity inside it. When the ball is heated the volume of the cavity will

   A.) remain unaffected
   B.) increase
   C.) decrease
   D.) have its shape changed

Answer: Option 'B'

The metal ball can be considered  to be made up of several layers of thinner ones. On heating each of these layers will increase in radius. As the inner most layer also increases its radius, the volume inside it i.e, the volume of the hollow portion will also increase.

13.

Radio waves sent out by a radio stations are reflected by

   A.) troposphere
   B.) stratosphere
   C.) mesosphere
   D.) ionosphere

Answer: Option 'D'

This is a layer of atmosphere about 60 to 70 km above the earth and extends to about 400km. It contains ionised particles which can reflect radio waves making radio communication round the world possible.

14.

Which of the following is a scalar quantity

   A.) Acceleration
   B.) Displacement
   C.) Electric field
   D.) work

Answer: Option 'D'

work

15.

Skating on ice is possible because 

   A.) the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water
   B.) the pressure on the ice due to skate raises its melting point
   C.) the surface of ice is smooth
   D.) ice is cold

Answer: Option 'A'

the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water
Here is a case of  lowering of melting point of ice with increase of pres

16.

Rolling friction is caused by ____ from the following?

   A.) Non-elastic effects
   B.) Gravity
   C.) Power dissipation
   D.) Buoyancy

Answer: Option 'A'

Rolling friction or rolling drag is the force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects, that is, not all the energy needed for deformation of the wheel, roadbed, etc... is recovered when the pressure is removed.

Another cause of rolling resistance lies in the slippage between the wheel and the surface, which dissipates energy.

17.

A nuclear reactor is said to have become 'critical' when 

   A.) it stops due to malfunctioning
   B.) it starts emitting dangerous radioactive radiations
   C.) it is shut down to avoid explosion
   D.) it is ready to produce controlled energy

Answer: Option 'D'

it is ready to produce controlled energy
To produce controlled energy i.e energy at a controlled or steady rate, the number of fissions per second must be controlled and maintained at that rate. Excess neutrons should be absorbed by control roads like cadmium.

18.

Earlist thermometerr was developed by

   A.) Kelvin
   B.) Galileo
   C.) Celsius
   D.) Fahrenheit

Answer: Option 'B'

Galileo

19.

When one enters a dark room after being in bright light one is not able to see anything clearly for a while because 

   A.) the retina of the eye moves forward
   B.) the retina of the eye moves backward
   C.) the iris is unable to dilate the pupil immediately to be able to see things
   D.) the eye has no power of accommodation

Answer: Option 'C'

The size of the pupil of the automatically adjusts itself according to the intensity of light passing through it; if the intensity is more, the size is less, if less, it is more. So in our case the pupil should dilate i.e , increase in size to be able to see in the dark. This switchover takes some time. But here the entry into the dark room is immediate. So the eye has no time to adjust itself and hence is not able to see at all for a while. 

20.

What is unit of Astronomical distance?

   A.) light year
   B.) angstrom
   C.) weber
   D.) lux

Answer: Option 'A'

angstrom is used to measure wave length,

weber is used to measure Magnetic flux,

lux is used to measure Intensity of illumination.


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