Question

(II) What is the internal resistance of a 12.0-V car battery whose terminal voltage drops to 8.8 V when the starter motor draws 95 A? What is the resistance of the starter?

Answer 1

Then the terminal voltage of the battery is,

Here, is the battery voltage, is the current flowing through the battery, and is the internal resistance of the battery.

Rewrite the equation for internal resistance.

Substitute for , for, and for.

Therefore, the internal resistance of the battery is.

Applying Ohm's law to the circuit, the voltage equals to IR.

Here,is the current flowing through the circuit, andis the resistance of the starter.

Rewrite the equation for resistance.

Substitute for, andfor.

Therefore, the resistance of the starter is.