Question

A voltmeter which can measure 2 V is constructed by using a galvanometer of resistance 12$\Omega$ and that produces maximum deflection for the current of 2 mA, then the resistance R is:

• A. 888 $\Omega$
• B. 988 $\Omega$
• C. 898 $\Omega$
• D. 999 $\Omega$

Answer 1

The correct option is B 988 $\Omega$

R = $\frac{V}{I_g}-G$

Putting V=2 V,$I_g$ = 2 mA = 2 X ${10}^{-3}$A, G = 12$\Omega$,

$\therefore$ $R=\frac{2}{2X{10}^{-3}}-12$ =1000 - 12= 988$\Omega$