An electric bulb is connected to 220 V generator. The current drawn is 600 mA. What is the power of the bulb?
- A.132 W
- B.13.2 W
- C.1320 W
- D.13200 W
Correct answer
Explanation
The correct answer is A, 132 W. Electric power is P = V × I, and 220 V × 0.6 A = 132 W.
Power is the rate at which electrical energy is used, measured in watts; one watt is one joule per second, or one volt times one ampere. The key step is the unit: 600 mA (milliampere) is 600 ÷ 1000 = 0.6 A. Two related forms are also tested: P = I²R and P = V²/R. For this bulb the resistance while glowing is V/I = 220 ÷ 0.6, about 367 ohms. Energy bills count kilowatt-hours: a 132 W bulb used for 1,000 hours uses 132 units.
B is wrong because 13.2 W would need a current of 0.06 A, or 60 mA, which comes from a slip in converting milliamperes.
C is wrong because 1320 W would need 6 A, ten times the given current.
D is wrong because 13200 W would need 60 A, which wrongly treats 600 mA as 60 A.
Exam tip: P = VI = I²R = V²/R; 1 A = 1000 mA; 1 unit = 1 kWh.
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