A-level Physics (Advancing Physics)/Internal Resistance/Worked Solutions
1. A 9V battery is short-circuited. The potential difference across the battery is found to be 8V, and the current is 5A. What is the internal resistance of the battery?
8 = 9 - 5Rinternal
5Rinternal = 1
Rinternal = 0.2Ω
2. What is the EMF of the battery in the following circuit?
Vexternal = 5 x 3 = 15 V
15 = E - (5 x 10)
E = 50 + 15 = 65 V
3. What is the internal resistance of the battery in the following circuit?
Vexternal = 7.5 x 3.75 = 28.125
Which actually makes this question impossible because the current is too high for the resistance supplied to the circuit.