The galvanometer deflection, when key K 1 is closed but K 2 is open, equals θ 0 (see figure). On closing K 2 also and adjusting R 2 to 5Ω , the deflection in galvanometer becomes 5 θ 0 .

Question

The galvanometer deflection, when key K 1 ​ is closed but K 2 ​ is open, equals θ 0 ​ (see figure). On closing K 2 ​ also and adjusting R 2 ​ to 5Ω , the deflection in galvanometer becomes 5 θ 0 ​ ​ . The resistance of the galvanometer is, then, given by [Neglect the internal resistance of battery]:

TestHub · Accepted Answer

θ ​ 0 ​ ∝ i G ​ ⇒ θ ​ 0 ​ C = i G ​ I-case C θ 0 ​ = 220 + R V ​ ......(i) II-case C 5 θ 0 ​ ​ = ( 220 + 5 + R 5 R ​ ) V ​ × 5 + R 5 ​ ....(ii) From (i) and (ii) R = 22Ω

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