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CBSE Class 12-science Answered

(i) Write two characteristics of a material used for making permanent magnets. (ii) Why is core of an electromagnet made of ferromagnetic materials? 2 OR Draw magnetic field lines when a (i) diamagnetic, (ii) paramagnetic substance is placed in an external magnetic field. Which magnetic property distinguishes this behaviour of the field lines due to the two substances?
Asked by Topperlearning User | 01 Jun, 2015, 02:05: PM
answered-by-expert Expert Answer

(i) Two characteristics of materials used for making permanent magnets:

(a)high retentivity so that the magnet is strong and

(b) high coercivity so that the magnetisation is not erased by stray magnetic fields, temperature fluctuations or minor mechanical damage.

 

(ii) Core of electromagnets are made of ferromagnetic materials because they have high permeability and low retentively. That is to ensure that heating losses are minimum as they will have narrow Hystersis curve.

OR

 

Magnetic field lines when a diamagnetic material is placed in external magnetic field:

 

 

Magnetic field lines when aparamagnetic material is placed in externalmagnetic field:

 

Propertythat is responsible for the above behaviour is magnetic dipole moment. Diamagnetic materialhas zero magnetic moment

Paramagnetic materialhas non zero magnetic moment

 

 

Answered by | 01 Jun, 2015, 04:05: PM
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