JEE Main20206 Sep 2020Evening ShiftPhysicsMagnetic Effects of CurrentActual
A square loop of side 2 a and carrying current I is kept in xz plane with its centre at origin. A long wire carrying the same current I is placed parallel to z -axis and passing through point 0 , b , 0 , b > > a . The magnitude of torque on the loop about z -axis will be :
Options
- A2 μ 0 I 2 a 2 πb
- B2 μ 0 I 2 a 2 b π a 2 + b 2
- Cμ 0 I 2 a 2 b 2 π a 2 + b 2
- Dμ 0 I 2 a 2 2 πb
Correct answer
B. 2 μ 0 I 2 a 2 b π a 2 + b 2
Step-by-step solution
Net force acting on wire AB & CD are zero τ = F 1 cosθ × 2 a = μ 0 2 π i 2 a 2 + b 2 ( 2 a ) × b a 2 + b 2 × 2 a τ = 2 μ 0 . i 2 a 2 b π a 2 + b 2