"A car battery has an e.m.f. of 12V and an internal resistance of 0.04 Ω. The starter motor draws a current of 100A. a.) What is the terminal p.d. of the battery when the starter motor is in operation? b.) If the headlamps are rated at 12V, 36W, what is their resistance? c.) To what value will their power output decrease when the starter motor is in operation?"
The Attempt at a Solution
The first two answers are easy to get. 8V and 4ohms. I can't get the last one( the lamps im assuming are in parallel). The book says the answer is 16W.