JEE Main202131 Aug 2021Morning ShiftPhysicsElectromagnetic InductionActual
A small square loop of side a and one turn is placed inside a larger square loop of side b and one turn ( b ≫ a ) . The two loops are coplanar with their centres coinciding. If a current I is passed in the square loop of side b , then the coefficient of mutual inductance between the two loops is :
Options
- Aμ 0 4 π 8 2 a 2   b
- Bμ 0 4 π 8 2 b 2 a
- Cμ 0 4 π 8 2   b
- Dμ 0 4 π 8 2 a
Correct answer
A. μ 0 4 π 8 2 a 2   b
Step-by-step solution
| B = 4 × μ 0 i 4 π b 2 2 ⇒ B = 2 2 μ 0 i π b ⇒ ϕ = M I ⇒ B A = M I ⇒ 2 2 μ 0 i π b · a 2 = M i ⇒ M = 2 2 μ 0 a 2 π b = μ 0 4 π 8 2 a 2 b