Question

A moving coil galvanometer has 150 equal divisions. Its current sensitivity is 10-divisions per milliampere and voltage sensitivity is 2 divisions per millivolt. In order that each division reads 1 volt, the resistance in ohms needed to be connected in series with the coil will be –

• A. 10⁵
• B. 10³
• C. 9995
• D. 99995

Answer 1

Answer: (C)

9995

Answer 2

I_g = 15 mA, V_g = 75 mV

\ R_g = $\frac{V_{g}}{I_{g}}$ = 5 W Required range of voltmeter = 150 volt

\ required series resistance R=$\frac{V}{I_{g}}$–R_g = $\frac{150}{15 \times 10^{- 3}}$ – 5

= 10,000 – 5 = 9995W