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

Answer: (B)

$5 \, \Omega$

Answer 2

Given: current sensitivity = 10 div/mA and there are 100 division on the scale.
$\therefore$ Current required for full scale deflection.
$I_{g} = \frac{1}{10} \times100\,mA = 10 \,mA$
$= 0.1 A$
Also voltage sensitivity = 2 div/mV
$\therefore$ voltage required for full scale deflection
$V_{g} = \frac{1}{2} \times100mV$
$= 0.05V$
Galvanometer resistance is given by
$G = \frac{V_{g}}{I_{g}} = \frac{0.05}{0.01}$
$= 5 \Omega$