Question

A galvanometer of resistance \( G \) is shunted by a resistance \( S \, \Omega \). To keep the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is

• A. \( \frac{S^2}{(S + G)} \)
• B. \( \frac{SG}{(S + G)} \)
• C. \( \frac{G^2}{(S + G)} \)
• D. \( \frac{S}{(S + G)} \)

Hint:

To maintain the current, use the formula for equivalent resistance in series and parallel combinations.

Answer 1

The Correct Option is C

In order to keep the main current in the circuit unchanged, the resistance in series must be calculated using the formula for equivalent resistance in parallel and series combinations.

Step 2: Conclusion.
The required resistance is \( \frac{G^2}{(S + G)} \), corresponding to option (c).