AB is a wire of uniform resistance. The galvanometer G shows no current when the length AC = 20cm and CB = 80 cm. The resistance R is equal to 

(1) 2 Ω

(2) 8 Ω

(3) 20 Ω

(4) 40 Ω

(3) By Wheatstone bridge, R80=ACBC=2080R=20Ω 

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