Electricity and Magnetism - Simple phenomena of magnetism

Magnetic poles: Magnets have two poles, North ($N$) and South ($S$). Like poles repel, while unlike poles attract.

Magnetic field lines: These represent the region where a magnetic force is exerted. Lines always point from the North pole to the South pole ($N \rightarrow S$).

Induced Magnetism: A magnetic material (like iron) becomes a magnet when placed in a magnetic field. This is temporary for 'soft' materials.

Soft Magnetic Materials: Materials like iron ($Fe$) that are easily magnetized but lose their magnetism easily. Ideal for electromagnets.

Hard Magnetic Materials: Materials like steel that are difficult to magnetize but retain their magnetism for a long time. Ideal for permanent magnets.

Methods of Magnetization: Stroking with a permanent magnet or placing the material inside a solenoid carrying a direct current ($DC$).

Methods of Demagnetization: Heating the magnet to high temperatures, hammering it while oriented in an East-West direction, or placing it in a solenoid with alternating current ($AC$) and slowly withdrawing it.

Electromagnets: Consist of a coil of wire (solenoid) wrapped around a soft iron core. The magnetic field strength increases with current ($I$) and the number of turns ($N$).