KCET 2025 Physics Paper

In an experiment to determine the figure of merit of a galvanometer using the half deflection method, a student set up a specific circuit. Here's a representation of that setup:During the experiment, the student initially removed a resistance of 5200Ω at point R. When switch K1 was closed and K2 remained open, the galvanometer showed a deflection of 26 divisions. With both K1 and K2 closed and a resistance of 90Ω removed at S , the galvanometer's deflection adjusted to 13 divisions.
To find the resistance of the galvanometer (G), we use the formula:
G=‌

S′

Q1 Q2 −1

Substituting the values into the formula:
G=‌

90

26 13 −1

This simplifies to:
G=90Ω≈91.6Ω
Thus, the approximate resistance of the galvanometer is 91.6Ω.