Question

By connecting a resistance of \(980 \Omega\) in series with a galvanometer, it is converted into a voltmeter of a certain range. When the resistance of \(470 \Omega\) is connected in series, the range is halved. The resistance of the galvanometer is

• A. \(30 \Omega\)
• B. \(40 \Omega\)
• C. \(50 \Omega\)
• D. \(60 \Omega\)

Hint:

The range V = Ig (G + R) halves when the series resistance changes from 980 to 470 ohm.

Answer 1

The Correct Option is B

Step 1: Take the ratio of ranges:
$\frac{V_1}{V_2} = \frac{G + 980}{G + 470} = 2$.

Step 2: Solve:
$G + 980 = 2G + 940$, so $G = 40\ \Omega$.

Final Answer:
$G = 40\ \Omega$, option (B). \[ \boxed{40\ \Omega} \]