Question

In a galvanometer 15% of the total current in the circuit passes through it. If the resistance of the galvanometer is G, then find out the shunt resistance S that is connected to the galvanometer.

(a) \(\frac {17G}{3}\)

(b) \(\frac {16G}{3}\)

(c) \(\frac {5G}{17}\)

(d) \(\frac {3G}{17}\)

I had been asked this question during an interview for a job.

I would like to ask this question from Moving Coil Galvanometer topic in section Moving Charges and Magnetism of Physics – Class 12

Answer 1

Correct option is (d) \(\frac {3G}{17}\)

Explanation: Ig = \((\frac {15}{100})\) × I

S = Ig × \(\frac {G}{I – I_g}\)

S = \( ( \frac {15}{100})\) × I × \(\frac {G}{(I – 15 \times \frac {I}{100})}\)

S = [0.15 × \( \frac {I}{(I – 0.15 \times I)} \) ] × G

S = [0.15 × \( \frac {I}{0.85 \times I} \) ] × G

S = \( \frac {15}{85} \) × G

S = \( \frac {3G}{17} \)

Therefore, the shunt resistance required is \( \frac {3G}{17} \).