Magnetic Induction is one of the ways making magnetic materials like steel and iron into magnets. In other words, magnetic induction is a process of inducing magnetism in an ordinary piece of magnetic material.
- This method involves simply placing the magnetic material (soft iron) close to a strong magnet without touching.
- The soft iron bar becomes an induced magnet with the end nearer the magnet having opposite polarity to that of the magnet.
- Hence, the soft iron bar is attracted and attached to the permanent magnet. Magnetic induction process reveals how magnetic materials can be attracted to magnets.
- Induced magnetism is a temporary process. If the permanent magnet is removed, the magnetic material will usually lose its induced magnetism.
Electrical method for magnetisation
For magnetization, a direct current flowing into a solenoid (a long insulated wire coiled into a cylinder) produces a magnetic field that, inside the coil, is uniform in strength and direction.
- The solenoid becomes a magnet.
A steel bar placed inside the coil for a short while becomes magnetised due to magnetic induction from the solenoid.
- The polarities of the magnet depend on the direction of current flow.
Magnetisation by electric current method creates more powerful magnets than other magnetization methods such as stroking.
Comparison between electromagnet and permanent magnet
|Made of a coil of wire (often with a soft iron core)||Made of hard magnetic material like steel|
|Magnetism is temporary. Requires a current through the coil to sustain the magnetic field strength||Magnetism is permanent. Does not require any electric current to retain magnetic field strength|
|Applications: Telephone receivers, electric relays, electric bells, circuit breakers||Applications: Magnetic doorstops, compasses, motors|