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

Mean radius of a Rowland ring, `r=15cm=0.15m`
Number of turns on a ferromagnetic core, `N=3500`
Relative permeability of the core material, `mu_(r)=800`
Magnetising current, `I=1.2A`.
The magneic field is given by the relation:
`B=(mu_(1)mu_(0)1N)/(2pir)`
where,
`mu_(0)=` permeabilityof free space=`4nxx10^(-7)Tm A^(-1)`
`B=(800xx4pixx10^(-7)xx1.2xx3500)/(2pixx0.15)=4.48T`
Therefore, the magnetic field in the core is 4.48T.