JEE Advanced2021PhysicsElectromagnetic InductionActual
Paragraph A special metal S conducts electricity without any resistance. A closed wire loop, made of S , does not allow any change in flux through itself by inducing a suitable current to generate a compensating flux. The induced current in the loop cannot decay due to its zero resistance. This current gives rise to a magnetic moment which in turn repels the source of magnetic field or flux. Consider such a loop, of
Options
- Am r 3
- Bm 2 r 2
- Cm r 2
- Dm 2 r
Correct answer
A. m r 3
Step-by-step solution
For a super conducting loop, net flux passing through it will remain constant. ϕ total   i = ϕ total   f As area is same, therefore, μ 0 m 2 πr 3 = μ 0 I 2 a ⇒ I = a m πr 3 ⇒ I ∝ m r 3