When a 20.0-ohm resistor is connected across the terminals of a 12.0-V battery, the terminal voltage of the battery falls 0.30 V. What is the internal resistance of this battery?

Question

Quizplus · Accepted Answer

The terminal voltage drop of 0.30 V indicates the voltage across the internal resistance. Using Ohm's law, the current through the circuit is I = 12.0 V / 20.0 Ω = 0.6 A. The internal resistance r can be found using V = I * r, so r = 0.30 V / 0.6 A = 0.5 Ω.

When a 200-Ohm Resistor Is Connected Across the Terminals of a 12