A car radio draws 0.27 A of current in the auto's 12-V electrical system. (a) How much electric power does the radio use? W (b) What is the effective resistance of the radio? Ω

Answer 1

The equation for electric power is either I²R or E² / R where I is current in amperes, E is voltage, and R is resistance. We are given E and I but not R, but we calculate the effective R using Ohm's Law, E +IR. Put the volts and amps into Ohm's Law and calculate the effective resistance.

Having determined resistance, use either of the power equations in get power in Watts.