Class 12 Physics
CBSE and UP Board
Magnetism and Matter
Chapter-5 Exercise 5.24
Additional Exercise
NCERT Solutions for Class 12 Physics Chapter 5 Question 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?
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Mean radius of a Rowland ring, r = 15 cm = 0.15 m
Number of turns on a ferromagnetic core, N = 3500
Relative permeability of the core material, μ =800
Magnetising current, I = 1.2 A
The magnetic field is given by the relation:
B = μrμ0 IN/2πr
Where, [μ0 = Permeability of free space = 4π x 10-7 T m A-1
B = (800 x 4π x 10-7 x 1.2 x 3500) / (2πx 0.15) =4.48 T
Therefore, the magnetic field in the core is 4.48 T.