(a) Consider the examples given in Ohm’s Law: Resistance and Simple Circuits and Resistance and Resistivity. Then find the power dissipated by the car headlight in these examples, both when it is hot and when it is cold.

(b) What current does it draw when cold?

Strategy for (a)

For the hot headlight, we know voltage and current, so we can use P = IV to find the power. For the cold headlight, we know the voltage and resistance, so we can use P = V²/R to find the power.