In a metre-bridge when a resistance in the left gap is 2 Ω and unknown resistance in the right gap, the balance length is found to be 40 cm. On shunting the unknown resistance with 2 Ω, the balance length changes by:
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Question

In a metre-bridge when a resistance in the left gap is 2 Ω and unknown resistance in the right gap, the balance length is found to be 40 cm. On shunting the unknown resistance with 2 Ω, the balance length changes by:

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G1 Physics · Accepted Answer

Initially: 2/X = 40/60 Therefore, X = 3 Ω After shunting X = 3 Ω with 2 Ω: X' = (2 × 3)/(2 + 3) = 1.2 Ω New balance condition: 2/1.2 = l/(100 - l) 2(100 - l) = 1.2l 200 = 3.2l l = 62.5 cm Change in balance length: 62.5 - 40 = 22.5 cm