A voltmeter has resistance of G and range of potential V. The value of resistance used in series to convert it into a voltmeter of range nV is-
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (n-1)G
To increase the range of a voltmeter, a high resistance R is connected in series. The full-scale current \( I_g \) through the meter stays the same, so the total resistance must rise in the same ratio as the range.
\( \displaystyle I_g = \frac{V}{G} \)
\( \displaystyle I_g(G + R) = nV \)
\( \displaystyle \frac{V}{G}(G + R) = nV \)
\( \displaystyle G + R = nG \)
\( \displaystyle R = (n - 1)G \)