Question

A galvanometer with a scale divided into 100 equal divisions has a current sensitivity of 10 divisions per milliampere and a voltage sensitivity of 2 divisions per millivolt. The galvanometer resistance will be

• A. $4\Omega$
• B. $5\Omega$
• C. $3\Omega$
• D. $7\Omega$

Answer 1

The correct option is B $5\Omega$

Given: current sensitivity = 10 div/mA and there are 100 division on the scale.
$\therefore$ Current required for full scale deflection.
$I_g=\frac{1}{10}\times 100mA=10mA=0.01A$
Also voltage sensitivity = 2 div/mV
$\therefore$ voltage required for full scale deflection
$V_g=\frac{1}{2}\times 100mV=0.05V$
Galvanometer resistance is given by
$G=\frac{V_g}{I_g}=\frac{0.05}{0.01}=5\Omega$