Question

A range of galvanometer is V, when $50\Omega$ resistance is connected in series. Its range gets doubled when $500\Omega$ resistance is connected in series. Galvanometer resistance is

• A. $100\Omega$
• B. $200\Omega$
• C. $300\Omega$
• D. $400\Omega$

Answer 1

Answer: (D)

$400\Omega$

Let the galvanometer resistance be $G$ and current flowing through it be $I_G$

$\therefore$ $V=I_G(G+R)$

Given : For $R=50\Omega$,

Galvanometer range is $V$

$\therefore$ $V=I_G(G+50)$ ..........(1)

For, $R=500\Omega$, Galvanometer range is $2V$

$\therefore$ $2V=I_G(G+500)$ ..........(2)

Dividing (2) from (1),

we get, $2=\frac{G+500}{G+50}$

$⟹$$G=400\Omega$