For a moving coil galvanometer, the deflection in the coil is 0.05 rad when a current of 10 mA is passed through it. If the torsional constant of suspension wire is N m rad, the magnetic field is 0.01T and the number of turns in the coil is 200, the area of each turn (in cm) is :
- A.1.0
- B.2.0
- C.1.5
- D.0.5
Show answer and solution
Correct option: A
Solution
At equilibrium, the deflecting torque equals the restoring torque:
NIAB = kθ
Solving for A:
A = kθ / (NIB) = (4.0×10⁻⁵ × 0.05) / (200 × 10×10⁻³ × 0.01)
= (2.0×10⁻⁶) / (2.0×10⁻²)
= 1.0×10⁻⁴ m² = 1.0 cm²
NIAB = kθ
Solving for A:
A = kθ / (NIB) = (4.0×10⁻⁵ × 0.05) / (200 × 10×10⁻³ × 0.01)
= (2.0×10⁻⁶) / (2.0×10⁻²)
= 1.0×10⁻⁴ m² = 1.0 cm²
[JEE Main 2023 · 25 Jan · Shift 2]