alleryWhich consumes more electrical energy: a 500 W TV set running for 30 minutes, or a 600 W heater running for 20 minutes?
AThe heater
BNeither uses energy
CBoth equal
DThe TV set
Answer & Solution
Correct answer: D. The TV set
1. Energy of the TV: $500\ \text{W} \times 0.5\ \text{h} = 250$ Wh.
2. Energy of the heater: $600\ \text{W} \times \dfrac{20}{60}\ \text{h} = 600 \times \dfrac{1}{3} = 200$ Wh.
3. Compare: 250 Wh > 200 Wh, so the TV set uses more energy.
4. The option The heater draws more power, but for a shorter time, so its total energy is less; power alone does not decide energy.
_Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 4 "Effects of Electric Current", p.70_
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