Question

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

• A. $(n-2)G$
• B. $(n-1)G$
• C. $(n-4)G$
• D. $(n-2)2G$

Answer 1

The correct option is B $(n-1)G$

Potential difference between A and B $V_{AB}=nV$

Current through galvanometer $I_g=\frac{V}{G}$

Using $V_{AB}=I_g(G+R)$

$\therefore$ $nV=\frac{V}{G}(G+R)$ $⟹R=(n-1)G$