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

Options

A. `100 Omega`
B. `200Omega`
C. `300Omega`
D. `400Omega`

Answer

D

Explanation

A galvanometer is converted into a voltmeter when a high resistance is connected to it in series. It l is maximum current flowing through galvanometer, then
`V=(R+G)l=(50+G)l` …..(i)
where, V is range of galvanometer
When `R = 50 Omega` is connected in series with it and G is galvanometer resistance.
When `500 Omega` resistance is connected in series, then range becomes double i.e, `2V=(500+G)l` ....(ii)
On dividing Eqs. (i) by (ii), we get
`(V)/(2V)=(50+G)/(500+G)`
or `500+G=100+2G rArr G = 400 Omega`