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)

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