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An ac has zero average, yet it heats a resistor. Why?
AThe wire stores charge each half cycle
BHeat comes only from the positive half
CHeating depends on i squared, never negative
DResistance rises when current reverses
Answer & Solution
Correct answer: C. Heating depends on i squared, never negative
Joule heating is i squared times R, and i squared stays positive for either direction of current, so its average is not zero.
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