What are permanent magnets? Give one example.

Explanation

Permanent magnets : Those magnets which can retain their magnetic properties for a long time at room temperature are called permanent magnets.
Electromagnets : A ferromagnetic substance placed inside a current carrying solenoid acts as an electromagnet.
Comparison of magnetic properties of permanent magnets and electromagnets :
1. The area of hysteresis loop for permanent magnetic is very large than for electromagnets. So when they are taken over a complete cycle of magnetisation, then loss of energy per unit volume is very large permanent magnets as compared to electromagnets.
2. Permanent magnets retain their magnetic properties for a long time at room temperature while electromagnets retain their magnetic properties till the electric current flows through them.
3. Materials used for making permanent magnet have high coercivity and retentivity while the materials used for making electromagnets have high retentivity but low coercivity.
Permanent magnets can e obtained by rubbing a ferromagnetic material with a magnet in a specific way.
This can also be obtained by placing a hard ferromagnetic bar in a current carrying solenoid. The magnetic field of solenoid magnetises the ferromagnetic material.