In Kelvin's method for galvanometer resistance using a metre bridge, the balance length opposite the galvanometer is $\ell_g = 60$ cm and the known resistance in the other gap is $R = 50\ \Omega$. The galvanometer resistance $G$ is:
A50 Ω
B33.3 Ω
C100 Ω
D75 Ω
Answer & Solution
Correct answer: D. 75 Ω
$G = R \cdot \ell_g/(100 - \ell_g) = 50 \times 60/40 = 75\ \Omega$.
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