A voltmeter has a resistance `G` and range `V`. Calculate the resistance to be used in series with it to extend its range to `nV`.

Explanation

With a voltmeter of range V volt, the current i is given by
`i=(V)/(G)ldots(i)`
To change it into voltmeter of range av volt, the necessary series resistance be R. Then`i=(lambdaV)/(R+G)ldots(ii)
Equating equations (i) and (ii) `(V)/(G)=(lambdaV)/(R+G)`
It gives `R = (lambda - 1)G`