Energy consumed by a 60-watt bulb in 2 minutes:
Correct answer: A. 7.2 kJ
- A. 7.2 kJ
- B. 720 J
- C. 120 J
- D. 72000 J
Explanation
P = 60W t = 2 minutes =2×60 seconds =120 seconds E= P×twhere ( E ) is the energy in joules (J), ( P ) is the power in watts (W), and ( t ) is the time in seconds (s). E=60 W×120 s E=7200 JSo, the energy consumed by a 60-watt bulb in 2 minutes is 7200 joules. As we want the answer in kilojoules (kJ), so we'll divide the energy in joules by 1000 because 1 kJ = 1000 J: E=7200/1000 J E=7.2 kJTherefore, the energy consumed is 7.2 kilojoules.
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Power is the rate at which work is done or energy is transferred, with average power calculated over a time interval and instantaneous power found from P = Fv when force and velocity are aligned. Work includes units, mechanical efficiency, and the distinction between power and total work or energy.
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