A galvanometer having internal resistance `10Omega` requires 0.01 A for a full-scale deflection. To convert this galvanometer to a voltmeter of full-scale deflection at 120 V, we need to connect a resistance of

Options

A. `11990Omega` in series
B. `11990Oemga` in parallel
C. `12010Omega` in series
D. `12010Omega` in parallel

Explanation

The internal resistance of the galvanometer (G) is `10Omega`. A high resistance R is to be added in series with galvanometer. In this case, if the galvanometer is connected between the two points A and B then the galvanometer will become a voltmeter of voltage range from 0 to `(V_(A)-V_(B))`.
According to Fig. 1.127, `V_(A)-V_(B)=I_(G)(G+R)`

`:.R(V_(A)-V_(B))/(I_(G))-G`
`=(120)/(0.01)-10`
`=12000-10=11990Omega`