A galvanometer has a coil of resistance `100Omega and ` gives a full scale deflection for 30 volt range, the resistance required to be added will be

Options

A. `900Omega`
B. `1800Omega`
C. `500Omega`
D. `1000Omega`

Answer

A

Explanation

Given,
Resistance of galvanometer,
`G=100Omega`
Current for full scale deflection,
`l_(g)=30mA=30xx10^(-3)A`
Range of voltmeter,
V=30V
To convert the galvanometer into an voltmeter of a given range, a resistance R is connected in series with it.

From figure,
`V=l_(g)(G+R)`
or `R=(V)/(l_(g))-G=(30)/(30xx10^(-3))-100Omega`
`=1000-100=900Omega`