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

Answer: (B)

988 $\Omega$

Answer 2

$\mathrm { R } = \frac { \mathrm { V } } { \mathrm { I } _ { \mathrm { g } } } - \mathrm { G }$

Putting $\mathrm { V } = 2 \mathrm {~V} , \mathrm { I } _ { \mathrm { g } } = 2 \mathrm {~mA} = 2 \times 10 ^ { - 3 } \mathrm {~A} , \mathrm { G } = 12 \Omega$

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