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Question : 14
Total: 26
(a) An iron ring of relative permeability µ 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.
(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.
Solution:
(a) Expression for Ampere's circuital law
Derivation of magnetic field inside the ring
(b) Identification of the material
Drawing the modification of the field pattern
(a)From Ampere's circuital law, we have,
∮
= µ 0 µ r I endosed ......(i)
For the field inside the ring, we can write
∮
= ∮
= B .2 π r ( r = radius of the ring )
Also, I enclosed = ( 2 π r n ) I using equation (i)
∴ B .2 π r = µ 0 µ r ⋅ ( n .2 π r ) I
∴ B = µ 0 µ r n I
(b) The material is paramagnetic. The field pattern gets modified as shown in the figure below.
Derivation of magnetic field inside the ring
(b) Identification of the material
Drawing the modification of the field pattern
(a)From Ampere's circuital law, we have,
For the field inside the ring, we can write
(b) The material is paramagnetic. The field pattern gets modified as shown in the figure below.
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