Power & Its Units — Homi Bhabha Exam Physics MCQs with Solutions
Free Homi Bhabha Exam Physics Power & Its Units MCQs with step-by-step solutions (8 questions). Part of Work, Energy & Power. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Power & Its Units · medium · numerical
A machine does 600 J of work in 4 s. Its power is:
A. 604 W
B. 2400 W
C. 150 W ✓ Correct
D. 0.0067 W
Solution: Power $= \dfrac{\text{work}}{\text{time}} = \dfrac{600}{4} = 150$ W.
Q2 — Power & Its Units · medium · theory
One watt is equal to:
A. 1 joule × 1 second
B. 1 joule per second ✓ Correct
C. 1 joule per metre
D. 1 newton per second
Solution: Power is the rate of doing work: 1 W = 1 J/s.
Q3 — Power & Its Units · hard · numerical
A boy of weight 400 N climbs a staircase of height 5 m in 10 s. His power is:
A. 2000 W
B. 200 W ✓ Correct
C. 20 W
D. 4000 W
Solution: Work $= 400 \times 5 = 2000$ J; power $= \dfrac{2000}{10} = 200$ W.
Q4 — Power & Its Units · hard · numerical
The number of joules in 1 kilowatt-hour (kWh) is:
A. 1000 J
B. 3,600,000 J ✓ Correct
C. 60,000 J
D. 3600 J
Solution: 1 kWh $= 1000$ W $\times 3600$ s $= 3.6 \times 10^6$ J.
Q5 — Power & Its Units · medium · theory
Two machines do the same amount of work, but machine A takes less time than machine B. Then:
A. machine B has greater power
B. power cannot be compared
C. machine A has greater power ✓ Correct
D. both have equal power
Solution: For the same work, less time means greater power ($P = W/t$).
Q6 — Power & Its Units · hard · numerical
A pump raises 100 kg of water to a height of 10 m in 20 s (taking $g = 10$ m/s²). Its power is:
A. 500 W ✓ Correct
B. 50 W
C. 250 W
D. 1000 W
Solution: Work $= mgh = 100 \times 10 \times 10 = 10000$ J; power $= \dfrac{10000}{20} = 500$ W.
Q7 — Power & Its Units · medium · numerical
An electric bulb rated 60 W is used for 1 minute. The electrical energy it consumes is:
A. 216000 J
B. 360 J
C. 60 J
D. 3600 J ✓ Correct
Solution: Energy $= P \times t = 60 \times 60 = 3600$ J.
Q8 — Power & Its Units · medium · theory
1 horsepower (hp) is approximately equal to:
A. 746 W ✓ Correct
B. 1000 W
C. 100 W
D. 1 W
Solution: 1 hp $\approx 746$ watts.