The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 Ω is:
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Question

The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 Ω is:

G1 Physics · Accepted Answer

Step 1: E = I(R+r). Step 2: r = E/I − R = 2.1/0.2 − 10 = 10.5 − 10 = 0.5 Ω.