A 50-turn circular coil of radius 2.0cm carrying a current of 5.0A is

1.	A 50-turn circular coil of radius 2.0cm carrying a current of 5.0A is rotated in a magnetic field of strength 0.20T. (a) What is the maximum torque that acts on the coil? (b) In a particular position of the coil, the torque acting on it is half of this maximum. What is the angle between the magnetic field and the plane of the coil?
Answer» n = 50, r = 0.02m A = π × (0.02)², B = 0.02T i = 5A, μ = niA = 50 × 5 × π × 4 × 10^–4 τ is max. when θ = 90° τ = μ × B = μBSin90° = μB = 50× 5 × 3.14 × 4 × 10^–4× 2 × 10^–1 = 6.28 × 10^–2N-M Given τ = (1/2)τ_max => Sinθ = (1/2) or, θ = 30° = Angle between area vector & magnetic field. => Angle between magnetic field and the plane of the coil = 90° – 30° = 60°

A 50-turn circular coil of radius 2.0cm carrying a current of 5.0A is rotated in a magnetic field of strength 0.20T. (a) What is the maximum torque that acts on the coil? (b) In a particular position of the coil, the torque acting on it is half of this maximum. What is the angle between the magnetic field and the plane of the coil?

Answer»

n = 50, r = 0.02m

A = π × (0.02)², B = 0.02T

i = 5A, μ = niA = 50 × 5 × π × 4 × 10^–4

τ is max. when θ = 90°

τ = μ × B = μBSin90° = μB = 50× 5 × 3.14 × 4 × 10^–4× 2 × 10^–1 = 6.28 × 10^–2N-M

Given τ = (1/2)τ_max

=> Sinθ = (1/2)

or, θ = 30° = Angle between area vector & magnetic field.

=> Angle between magnetic field and the plane of the coil = 90° – 30° = 60°