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Question (21)

QN006382

A machine does 15000 J work in 50 s. Find power.

(A) 3 W
(B) 30 W
(C) 300 W
(D) 3000 W

Correct Answer: C

Explanation:

Power = 15000 ÷ 50 = 300 W

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Question (22)

QN006383

The unit kilowatt-hour measures:

(A) Power
(B) Force
(C) Energy
(D) Velocity

Correct Answer: C

Explanation:

kWh is a unit of energy.

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Question (23)

QN006384

A person climbs stairs doing 2400 J work in 40 s. Power developed is:

(A) 60 W
(B) 600 W
(C) 96000 W
(D) 24 W

Correct Answer: A

Explanation:

Power = 2400 ÷ 40 = 60 W

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Question (24)

QN006385

A powerful engine is preferred because it can:

(A) Reduce mass
(B) Increase time taken
(C) Do more work in less time
(D) Reduce displacement

Correct Answer: C

Explanation:

Greater power means faster work.

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Question (25)

QN006386

A machine of 500 W power works for 10 s. Work done is:

(A) 50 J
(B) 5000 J
(C) 500 J
(D) 5 J

Correct Answer: B

Explanation:

Work = Power × Time = 500 × 10 = 5000 J

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Question (26)

QN006387

Which physical quantity is represented by watt?

(A) Work
(B) Energy
(C) Power
(D) Force

Correct Answer: C

Explanation:

Watt is the SI unit of power.

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Question (27)

QN006388

A motor performs 7200 J work in 12 s. Its power is:

(A) 60 W
(B) 600 W
(C) 720 W
(D) 86400 W

Correct Answer: B

Explanation:

Power = 7200 ÷ 12 = 600 W

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Question (28)

QN006389

If work done remains same and time increases, power:

(A) Increases
(B) Decreases
(C) Remains same
(D) Becomes zero

Correct Answer: B

Explanation:

Power decreases when time increases.

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Question (29)

QN006390

A 2 kW heater operates for 1 second. Energy used is:

(A) 2 J
(B) 20 J
(C) 200 J
(D) 2000 J

Correct Answer: D

Explanation:

Energy = 2000 × 1 = 2000 J

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Question (30)

QN006391

Which appliance generally has highest power rating?

(A) LED bulb
(B) Ceiling fan
(C) Electric heater
(D) Wrist watch

Correct Answer: C

Explanation:

Electric heaters have high power ratings.

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Question (21)

A machine does 15000 J work in 50 s. Find power.

Explanation:

Link:

Question (22)

The unit kilowatt-hour measures:

Explanation:

Link:

Question (23)

A person climbs stairs doing 2400 J work in 40 s. Power developed is:

Explanation:

Link:

Question (24)

A powerful engine is preferred because it can:

Explanation:

Link:

Question (25)

A machine of 500 W power works for 10 s. Work done is:

Explanation:

Link:

Question (26)

Which physical quantity is represented by watt?

Explanation:

Link:

Question (27)

A motor performs 7200 J work in 12 s. Its power is:

Explanation:

Link:

Question (28)

If work done remains same and time increases, power:

Explanation:

Link:

Question (29)

A 2 kW heater operates for 1 second. Energy used is:

Explanation:

Link:

Question (30)

Which appliance generally has highest power rating?

Explanation:

Link:

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