Practice MCQ Questions and answers on Physics-GK

71

During hot weather, the fan produces a feeling of comfort. This is because

A) Fan supplies cool air B) Fan cools the air C) Our perspiration eva-porates rapidly D) Conductivity of air increases

Discuss

Answer & Solution

Answer: Option C

Solution:

During hot weather, the fan produces a feeling of comfort. This is because our perspiration evaporates rapidly.

72

The flow of thermal energy is called

A) Heat B) Current C) Voltage D) Potential

Discuss

Answer & Solution

Answer: Option A

Solution:

The term conduction refers to the transfer of energy. Conduction occurs when energy is passed between objects. The transfer of thermal energy is called heat.

73

On a cold day when the room temperature is 15°C, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15°C, because :

A) Metals have higher thermal capacity than plastics B) Plastics have a lower density than metals C) Metals are good conductors of heat D) Plastics have a higher thermal conductivity than metals

Discuss

Answer & Solution

Answer: Option C

Solution:

On a cold day when the room temperature is 15°C, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15°C, because metals are good conductors of heat.

74

Which of the following is an insulator?

A) Mercury B) Carbon C) Germanium D) Glass

Discuss

Answer & Solution

Answer: Option D

Solution:

Glass is an insulator.

75

'Therm' is the unit of

A) Power B) Heat C) Light D) Distance

Discuss

Answer & Solution

Answer: Option B

Solution:

'Therm' is the unit of heat.

76

Heat flows as a result of difference of ________

A) Temperature B) Density C) Mass D) Volume

Discuss

Answer & Solution

Answer: Option A

Solution:

Heat flows as a result of difference of temperature.

77

Light beam which is highly directional is called:

A) Eraser B) Grazer C) Maser D) Laser

Discuss

Answer & Solution

Answer: Option D

Solution:

Light beam which is highly directional is called laser.

78

Speed of light is maximum in ________

A) Vacuum B) Solids C) Liquids D) Gases

Discuss

Answer & Solution

Answer: Option A

Solution:

Light travels faster in vacuum as compared to any other medium. This is because there is no obstruction in the propagation of light in vacuum as there is no matter in vacuum and also, because the refractive index of vacuum is the lowest i.e. equal to unity.

79

Light travels in a straight line (rectilinear propagation of light). This statement does hold if the medium of travel for light is

A) Of variable refractive index B) Made up of slabs of different refractive indices C) Homogeneous and transparent D) Inhomogeneous and transparent

Discuss

Answer & Solution

Answer: Option C

Solution:

Light travels in a straight line (rectilinear propagation of light). This statement does hold if the medium of travel for light is homogeneous and transparent.

80

The speed of light will be minimum while passing through

A) Water B) Vaccum C) Air D) Glass

Discuss

Answer & Solution

Answer: Option D

Solution:

Light travels at approximately 300,000 kilometers per second in a vacuum, which has a refractive index of 1.0, but it slows down to 225,000 kilometers per second in water and 200,000 kilometers per second in glass.