Practice MCQ Questions and answers on Physics-GK

41

1 Joule is Equal to

A) 10^3 ergs B) 10^6 ergs C) 10^7 ergs D) 10^5 ergs

Discuss

Answer & Solution

Answer: Option C

Solution:

1 Joule is equal to 10^7 ergs.

42

A dynamo is a device which

A) Creates mechanical energy B) Creates electrical energy C) Converts mechanical energy into electrical energy D) Converts electrical energy into mechanical energy

Discuss

Answer & Solution

Answer: Option C

Solution:

Dynamo is a device that converts mechanical energy into electrical energy. Its other name is electric generator. A device which has a reversed effect to this is the electric motor. An electric motor is a device which converts electric energy to mechanical energy.

43

A dynamo is used to convert

A) Mechanical energy into electrical energy B) Electrical energy into mechanical energy C) Electrical energy into magnetic energy D) Magnetic energy into mechanical energy

Discuss

Answer & Solution

Answer: Option A

Solution:

A dynamo is used to convert mechanical energy into electrical energy.

44

A photo-electric cell converts

A) Mechanical energy to electric energy B) Heat energy to mechanical energy C) Light energy to chemical energy D) Light energy to electrical energy

Discuss

Answer & Solution

Answer: Option D

Solution:

A photo-electric cell converts light energy to electrical energy.

45

Dynamo is a device for converting

A) Heat energy into electrical energy B) Mechanical energy into electrical energy C) Magnetic energy into electrical energy D) Chemical energy into electrical energy

Discuss

Answer & Solution

Answer: Option B

Solution:

Dynamo is a device for converting mechanical energy into electrical energy.

46

For a freely falling body, the sum of kinetic energy and potential energy is always

A) Zero B) Unity C) Same D) Variable

Discuss

Answer & Solution

Answer: Option C

Solution:

The sum total of the potential energy and the kinetic energy of the object during its free fall remains the same, i.e., the total mechanical energy (potential energy + kinetic energy) remains constant. Thus, the law of conservation of energy is not violated.

47

A body of 4.0 kg is lying at rest. Under the action of a constant force, it gains a speed of 5 m/s. The work done by the force will be ________

A) 50 J B) 30 J C) 20 J D) 40 J

Discuss

Answer & Solution

Answer: Option A

Solution:

Work done = 1/2*m*V²
=1/2*4*5²
= 1/2*4*25
= 2*25
= 50 J

48

If the velocity of a body is halved its kinetic energy ________

A) Become 4 times B) Becomes 1/4 th C) Is also doubled D) Becomes half

Discuss

Answer & Solution

Answer: Option B

Solution:

When velocity is halved, its kinetic energy becomes 1/4th.

49

Solar energy is converted into chemical energy during

A) Transpiration B) Photosynthesis C) Diffusion D) Osmosis

Discuss

Answer & Solution

Answer: Option B

Solution:

Solar energy is converted into chemical energy during photosynthesis.

50

In which of the following cases, kinetic energy is being used in performing work ?

A) Paddling the bicycle to cover a distance B) Driving a car to cover a distance C) Wind mill grinding wheat grain D) Rowing a boat in the lake

Discuss

Answer & Solution

Answer: Option B

Solution:

In driving a car to cover a distance, kinetic energy is being used in performing work.