Question

The material used for permanent magnet has
A) Low retentivity, high coercivity
B) High retentivity, low coercivity
C) High retentivity, high coercivity
D) Low retentivity, low coercivity

Answer 1

Hint: Permanent magnets just like the other magnets have two poles: the North pole and South pole. Retentivity and coercivity are the properties of the magnet which helps in determining the strength of the magnet. These are the abilities of the magnet to stay in some other state or come back in its original state.

Complete step by step answer:
Step I:
In order to make a good permanent magnet, it should have a high value of retentivity and a high value of coercivity.
Retentivity is the ability of the magnetic material by which the magnetic field remains in the material even after removing the source of the external magnetic field. Whereas, coercivity or coercive force is the minimum amount of magnetic intensity needed to bring back the magnet in a state where the magnetic field is zero is known as coercivity.

Here $B$ refers to the retentivity of the magnet and $H$ shows the coercive power of the magnet. A hysteresis loop is used to show the relation between magnetic force $B$ and magnetic flux $H$.
Step II:
Permanent magnets do not require an external magnetic field. They produce their own magnetic field which is available all the time. Some examples of permanent magnets are steel and alnico. Due to their ability to produce their own magnetic fields, they are used in hard drives, phones, sensors, generators, and many other electronics.

Permanent magnets have high values of retentivity and coercivity. Therefore, Option (C) is the correct answer.

Note:
Sometimes there arises a question, whether permanent magnets are similar to electromagnets or not? So, they both are different. A permanent magnet creates its own magnetic field. But an electromagnet is a coil of wire which behaves like a magnet when a current is made to pass through it.