(a) An iron ring of relative permeability `mu_(r)` has windings of insulated copper wire of n turns per metre. When the current in the windings is I, find the expression for the magnetic field in the ring.
(b) The susceptibility of a magnetic material is 0.9853. Identify the type of magnetic material. Draw the modification of the field pattern on keeping a piece of this material in a uniform magnetic field.

Explanation

From Ampere.s circuital ,we have
` oint oversetto B d oversetto I =mu _ 0 mu , I_("enclosed") `
For the field inside the ring , we can write
`oint oversetto B d oversetto I =oint Bdl =B = 2pi r`
( r= radius of the ring ) using equation (i)
` therefore B = 2pi , = mu _0 mu_r .(2pin)l`
` therefore B= mu _ 0 mu_tnl `
[Award those `((1)/(2) + ( 1) /(2)) `make even file the result is written without giving the derivation]