Real Batteries

Internal resistance and maximum power

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Terminal voltage $V = \varepsilon - Ir$ falls as current rises.
• Maximum power reaches the load when its resistance equals the internal resistance.
• At that point efficiency is only 50%.

Steps

1. Not quite ideal
2. Terminal voltage
3. Dimming headlights
4. Maximum power
5. Short circuit
6. Matching for efficiency?