Discuss the difference between a permanent magnet and an ele

Discuss the difference between a permanent magnet and an electromagnet. What are some practical applications of each? Discuss why a conductor and the external field must be perpendicular to each other to have motor action or to generate induced voltage.

Solution

Difference between a permanent magnet and an electromagnet are

b) Explanation of why conductor and the external filed must be perpendicular to each other to have motor action and to generator induced voltage

Motor action is development of torque which can be possible only when external field and conductors are in perpendicular this is because of Torque developed is cross product of main field and rotor field which is given below

T = K*main field*conductor filed*sin(delta)

where delta is angular difference between main filed and conductor filed. Conductor field is obtained when current is passing through it using right hand thumb rule magnetic field surround it.

For maximum torque delta should be 90⁰ which means both fileds should be perpendicular.

Generator action is development of voltage when conductor is along the field then the conductor will cut any filed there by no induced emf where as when conductor is perpendicular to magnetic field then there will more magnetic field cutting which leads to induce of high voltage.

Thus to develop high torque in motor and to induce high voltage in generator main filed and conductor should be perpendicular.

Permanent Magnet	Electromagnet
1) Permanent Magnets are formed using Hard Ferromagnetic Materials.	1) Electromagnets are formed using Soft Ferromagnetic Material.
2) Permanent Magnets are formed by frequently heating to high temperature and then quenched in suitable liquid to introduce strains in Hard Ferromagnetic Materials.	2) Electromagnetics are formed carefully to get desired properities by heating and slow annealing of soft ferromagneic material.
3) These permanent magnets have low permeability and very high coercive force. Once magnetized they cannot be demagnetized.	3) These Electromagnets have high relative permeability, low coercive force and can be easily magnetized and demagnetized.
4) Applications of Permanent magnets are used in permanent magnet Dc Macines, loud speakers etc	4) Electromagnets are used in Dc machines , relays, transformers, telephonic receivers etc