A Rowland ring of mean radius 15 cm has 3500 turns of wire wound on a ferromagnetic core of relative permeability 800. What is the magnetic field B in the core for a magnetising current of 1.2 A ?

Explanation

Here r = 15 cm `= 15 xx 10^(-2)m, N = 3500, M_(r) = 800`
`I = 1.2A, B = ?`
Number of turns, length, `n = (N)/(2pi r) = (3500)/(2pi xx 15 xx 10^(-2))`
`B = mu_(0) mu_(r) nI`
`= 4pi xx 10^(-7) xx 800 xx (3500 xx 1.2)/(2pi xx 15 xx 10^(-2))`
`= 4.48 T`