Question

A galvanometer, with a scale divided into $100$ equal divisions, has a current sensitivity of $10\text{div per mA}$ and voltage sensitivity $2\text{div per mV}.$ To read $5A$ full scale deflection

• A. Shunt resistance should be $1\Omega$
• B. Shunt resistance should be $0.1\Omega$
• C. Shunt resistance should be $0.01\Omega$
• D. Shunt resistance should be $0.001\Omega$

Answer 1

The correct option is C Shunt resistance should be $0.01\Omega$

$I_g=\left(\frac{1mA}{10div}\right)\left(100div\right)=10mA{V}_g=\left(\frac{1mV}{2div}\right)\left(100div\right)=50mVG=\frac{V_g}{I_g}=\frac{50}{10}=5\Omega$

$I$(current to be measured):-$5A$

$n=\frac{I}{I_s}=\frac{5A}{10mA}=500$

$\therefore s=\frac{G}{n-1}=\frac{5}{500-1}=1\times {10}^{-2}\Omega$