Question

Question 5.24: 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?

Class 12 - Physics - Magnetism And Matter Magnetism And Matter Page-203

Answer 1

number of turns , N = 3500
radius of Rowland ring , r= 15cm = 0.15 m
relative permeability, $\mu_r$=800
current, I = 1.2A

we know, magnetic in the core is given by
$B=\mu_mni=\frac{\mu_mNi}{2\pi r}$
because relative permeability = permeability of medium/permeability of vacuum
$\mu_r=\frac{\mu_m}{\mu_0}\\\mu_m=\mu_0\mu_r$
so,$B=\frac{\mu_0\mu_rNI}{2\pi r}$
= 4π × 10^-7 × 800 × 3500 × 1.2/(2π × 0.15)
= 4.48T

hence, magnetic field ,B = 4.48T