Question

A moving coil galvanometer has a resistance of 900 $\Omega$. In order to send only 10% of the main current through this galvanometer, the resistance of the required shunt is

• A. 0.9 $\Omega$
• B. 100 $\Omega$
• C. 405 $\Omega$
• D. 90 $\Omega$

Answer 1

The correct option is B 100 $\Omega$

Shunt resistance, $S=\frac{I_{g}G}{I-I_g}$

where $I_g$ is the full scale deflection current of the galvanometer, $I$ is the maximum current to be read on the ammeter.

$I_g=0.1I,I_s=0.9I;S=I_g{R}_g/I_s$

$=0.1\times 900/0.9=100\Omega$