Question

A rectangular coil of 100 turns has length 5 cm and width 4 cm. It is placed with its plane parallel to a uniform magnetic field and a current of 2 A is sent through the coil. Find the magnitude of the magnetic field B if the torque acting on the coil is 0.2 N m⁻¹

Answer 1

Given:
No. of turns in the coil, n = 100
Area of the coil, A = 5 × 4 cm² = 20 × 10⁻⁴ m²
Magnitude of current = 2 A
Torque acting on the coil, τ = 0.2 N m⁻¹
 τ = niA × B
⇒τ = niBA sin 90°
⇒ 0.2 = 100 × 2 ×20 × 10⁻⁴ × B
⇒ B = 0.5 T