Question

If the current sensitivity of a galvanometer is doubled, then its voltage sensitivity will be

• A. doubled
• B. halved
• C. unchanged
• D. four times

Answer 1

The correct option is C unchanged

Current sensitivity of galvanometer is deflection per unit current i.e
$\frac{\varphi }{I}$ = $\frac{NAB}{k}$..................(i)
Similarly voltage sensitivity is deflection per unit voltage
i.e. $\frac{\varphi }{V}$ = $\frac{NAB}{k}\frac{I}{V}$= $\frac{NAB}{k}\frac{1}{R}$..................(i)
From (i) and (ii)
Voltage sensitivity = current sensitivity X $\frac{1}{resistance}$
Now if current sensitivity is doubled, then the resistance in the circuit will also be doubled since it is proportional to the length of the wire, then voltage sensitivity
= (2 x current sensitivity) X $\frac{1}{2\times resistance}$
= (current sensitivity) X $\frac{1}{resistance}$
Hence, voltage sensitivity will remain unchanged.