Question

Two concentric circular coils one of small radius r1

Answer 1

Mate can u pls complete the question it's incomplete!!?

Answer 2

$\sf\red{N_1 = no. \: of \: turns \: per \: unit \: length \: of \: inner \: coil}\\\sf\red{N_2 = no. \: of \: turns \: per \: unit \: length \: of \: outer \: coil}\\\sf\red{r_1 and r_2 radius}\\\sf\red{L= length of coil (both)}\\\sf\red{L_1 = current flowing in inner coil}\\\sf\red{Magnetic field B due to this current}\\\sf\red{Bis only inside coil 1 }\\\sf\red{Outside coil IB=0}\\\sf\red{Magnetic flux through I turn of coil 2 due to B is}\\\sf\red{ϕ=B × Area = μ_0n_1i_1 × z^r_2}\\\sf\red{Total no. of turns in coil 2=n_2 × L}\\\sf\red{Mutual inductance M is ϕ = M × i}\\\sf\red{So, M=μ_0n_1n_2zr^2L}$