Question

Core of electromagnets is made of ferromagnetic material which has:
A. High permeability and low retentivity
B. High permeability and high retentivity
C. Low permeability and high retentivity
D. Low permeability and low retentivity

Answer 1

Hint: For designing electromagnets, the material used should get magnetized and demagnetized easily; also it should support the formation of magnetic fields within itself. Ferromagnetic materials produce strong magnetic effects. One of the substances we often use is Soft iron.

Complete step by step answer:
An electromagnet is a coil of wire wrapped around an iron core. Electromagnet is a type of magnet in which a magnetic field is generated by an electric current. Current passing through the wire creates a magnetic field which is concentrated at the center of the coil. An electromagnet with a ferromagnetic core can produce very strong magnetic effects.
Properties of the material used in making electromagnets are:-
The material should be of high permeability so that it supports the formation of magnetic fields within itself.
The material should have low retentivity so that it can get demagnetized easily.
For an electromagnet to be much strong, it should have a high value of saturation magnetization.
The material should have low coercivity.
Hysteresis loss should be small. The material should not get heated up during the process of magnetization and demagnetization.
Core of electromagnets are made from ferromagnetic materials that have high permeability and low retentivity. One of the best suited materials for this is Soft iron.
Hence, the correct option is A.

Additional information:
A permanent magnet is an object made with the help of a material which is magnetized and then it creates its own persistent magnetic field while an electromagnet is made with a coil of wire that acts as a magnet only when an electric current passes through it.
The main advantage of using electromagnet over permanent magnet is that in electromagnet, magnetic fields can be quickly changed by just controlling the amount of electric current in the winding. However, unlike a permanent magnet which needs no power to work, electromagnet requires a continuous supply of electric current to maintain the main advantage.

Note:
Students should remember that for making permanent magnets we use material having high coercivity and high retentivity for its strong magnetization, while electromagnetic materials have low coercivity and low retentivity. For that purpose we use ferromagnetic materials of high permeability, low coercivity, and low retentivity to design electromagnets.