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Magnetism And Matter

Question
CBSEENPH12037814

A solenoid of 500 turns per metre is carrying a current of 3A. Its core is made of iron, which has a relative permeability of 5000. Determine the magnitudes of magnetic intensity, magnetisation and magnetic field inside the core.

Solution

Given,
Number of turns in solenoid, n = 500
Current carried, I = 3A
Relative premeabiltiy of iron core,  μr = 5000 

Therefore, 
Magnetic intensity, 
                      H = ni     = 500 × 3     = 1500 Am-1 

Using the relation between susceptibility and permeability,
                 μr = 1+χcm

             χm = μr-1 = 5000-1      =4999  5000

Also,            μr = μμ0      = 5000 

               μr = 5000 μ0 

Magnetisation,  I = XmH 

                       = 5000 × 1500 = 7.5 × 106 Am-1 

Magnetic field inside the core is given by, 
              B = μH     = 5000 μ0 H                   μ = μ0H                     = 5000 (4π × 10-7) × 1500 

 i.e.,        B = 3π    = 3 ×227   = 9.4 T.