A 250-turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85 μ A and subjected to magnetic field of strength 0.85 T. Work done for rotating the coil by 180° against the torque is:-

Question

A 250-turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85 μ A and subjected to magnetic field of strength 0.85 T. Work done for rotating the coil by 180° against the torque is:- (A) 4.55 μ J (B) 2.3 μ J (C) 1.15 μ J (D) 9.1 μ J

Tardigrade Admin · Accepted Answer

W=M B( cos θ1- cos θ2) When it is rotated by angle 180° then W =2 M B W =2(N I A) B =2 × 250 × 85 × 10-6[1.25 × 2.1 × 10-4] × 85 =9.1 μ J

Q. A $250 -$ turn rectangular coil of length $2.1 c m$ and width $1.25 c m$ carries a current of $85 μ A$ and subjected to magnetic field of strength $0.85 T$ . Work done for rotating the coil by $18 0^{\circ}$ against the torque is:-

$4.55 μ J$

$2.3 μ J$

$1.15 μ J$

$9.1 μ J$

$W = MB (cos θ_{1} - cos θ_{2})$
When it is rotated by angle $18 0^{\circ}$ then
$W = 2 MB$
$W = 2 (N I A) B$
$= 2 \times 250 \times 85 \times 1 0^{- 6} [1.25 \times 2.1 \times 1 0^{- 4}] \times 85$
$= 9.1 μ J$

Q. A 250−turn rectangular coil of length 2.1cm and width 1.25cm carries a current of 85μA and subjected to magnetic field of strength 0.85T. Work done for rotating the coil by 180∘ against the torque is:-

4.55μJ

2.3μJ

1.15μJ

9.1μJ