Q.

Find the mutual inductance in the arrangement, when a small circular loop of wire of radius 'R' is placed inside a large square loop of wire of side L (L>>R). The loops are coplanar and their centres coincide.                  [2023]

1 M=2μ0R2L  
2 M=22μ0RL2  
3 M=22μ0R2L  
4 M=2μ0RL2  

Ans.

(3)

ϕ=Mi  also  ϕ=BA

ϕ=πR2(4μ04πi(L/2)2)

  M=22μ0R2L