JEE Main20207 Jan 2020Morning ShiftPhysicsMagnetic Effects of CurrentActual
A long solenoid of radius R carries a time t dependent current I t = I 0 t 1 - t . A ring of radius 2 R is placed coaxially near its middle. During the time interval 0 ≤ t ≤ 1 , the induced current I R and the induced E M F V R in the ring change as:
Options
- ADirection of I R remains unchanged and V R is maximum at t = 0.5
- BAt t = 0.25 direction of I R reverses and V R is maximum
- CDirection of I R remains unchanged and V R is zero at t = 0.25
- DAt t = 0.5 direction of I R reverses and V R is zero
Correct answer
D. At t = 0.5 direction of I R reverses and V R is zero
Step-by-step solution
I = I 0 t - I 0 t 2 ϕ = B A ϕ = μ 0 n I A V R = - d ϕ d t = - μ 0 n A I 0 1 - 2 t V R = 0 at t = 1 2 And I R = V R R e s i s t a n c e  o f  l o o p = 0