A balanced bridge is shown in the circuit diagram. The metre bridge wire has resistance 1 cm ⁻¹ . The current drawn from the battery is (Internal resistance of battery is negligible)

Step-by-step solution

Wire has a resistance 1 cm ⁻¹ . Resistance of 40 ~cm of wire =40 and resistance of 60 ~cm of wire =60 No current flows through the galvanometer since the bridge in balanced. Hence the branch containing the galvanometer can be removed. For balanced bridge 4 40 = Y 60 Y = 4 60 40 =6 4 and 6 are in series. Their equivalent resistance is 10 . 40 and 60 are in series. Their equivalent resistance is 100 . 10 and 100 are in parallel Their equivalent resistance is 1000 110 . The current I= V R = 6 110 1000 =0.66 ~A