To measure the internal resistance of a battery, the potentiometer is used. For R = 10 Ω, the balance point is observed at ℓ = 500 cm and for R = 1Ω the balance point is observed at ℓ = 400 cm. The internal resistance of the battery is approximately :
1
0.2 Ω
2
0.4 Ω
3
0.1 Ω
4
0.3 Ω