Question Detail
Question
A galvanometer has spring constant 'k', a magnetic field 'B' and deflection angle ?. The coil has N turns and an area A. Which of the following is the condition for equilibrium of the coil when current i flows in the galvanometer.
Correct Answer
Option B is the correct answer.
Detailed Explanation
In a galvanometer, the deflecting torque (τ_magnetic) due to the magnetic field is given by τ_magnetic = N I A B (assuming the magnetic field is radial, so sin(90°) = 1). The restoring torque (τ_spring) due to the spring is proportional to the deflection angle (?): τ_spring = k?.At equilibrium, the deflecting torque equals the restoring torque: τ_magnetic = τ_spring.Therefore, BIAN = K?.
Hint
At equilibrium, the magnetic torque on the coil balances the restoring torque from the spring. Recall the formulas for both torques.