Question

A galvanometer has resistance of 10 ohms and a full scale deflection is produced by 5 milli amperes. What is the value of resistance that should be connected in series with it in order to enable it to read 2V?

(a) 20 Ω

(b) 10 Ω

(c) 40 Ω

(d) 30 Ω

I got this question in a job interview.

I want to ask this question from Moving Coil Galvanometer topic in chapter Moving Charges and Magnetism of Physics – Class 12

Answer 1

Correct answer is (d) 30 Ω

Easy explanation: Given: G = 10 Ω; V = 2 V; Ig = 0.05 A

The required equation ➔ Ig = \(\frac {V}{(R + G)}\)

0.05 = \(\frac {2}{(R + 10)}\)

(R + 10) = \(\frac {2}{0.05} = \frac {200}{5}\) = 40

R = 40 – 10

R = 30 Ω