An electric heater is designed to operate in a 100 V main with a power output of 1000 W. When it is connected to a 25 V source, the power output is:
Correct answer: C. 62.5 W
- A. 40 W
- B. 100 W
- C. 62.5 W
- D. 250 W
Explanation
Calculate the heater's resistance using its values: R = V²/P = (100V)² / 1000W = 10 Ω. Now, calculate new power output at the lower voltage: P' = (V')²/R = (25V)² / 10Ω = 62.5 W.
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About Current Electricity
Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.
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