JEE Main 2024 Physics question
A moving coil galvanometer has 100 turns and each turn has an area of 2.0 cm. The magnetic field produced by the magnet is 0.01 T and deflection in the coil is 0.05 radian when a current of 10 mA is passed through it. The torsional constant of the suspension wire is x × N-m/rad. The value of x is .
Answer: 4
Solution
NIAB = kφ ⇒ k = 100 × 0.01 × 2 × 10⁻⁴ × 0.01/0.05 = 4 × 10⁻⁵ N m/rad.