| English | Electromagnet |
|---|---|
| Bahasa Melayu | Elektromagnet |
| 中文 | 电磁铁 |
Definition
A magnet made by passing an electric current through a coil, usually wound around a soft iron core, whose magnetism can be switched on and off.
In exam terms
An electromagnet is a magnet produced by passing an electric current through a coil (solenoid), usually wound around a soft iron core. It has no fixed SI unit or symbol of its own because it is a device, not a physical quantity, but its magnetic effect depends on quantities you can control.
The strength of an electromagnet increases when you increase the current, increase the number of turns per unit length of the coil, or use a soft iron core instead of an air core. Example of correct use: Increasing the current from 1 A to 2 A makes the electromagnet lift more iron nails. Its great advantage is that the magnetism can be switched on and off, and its polarity reversed by reversing the current direction.
Do not confuse it with…
Do not confuse an electromagnet with a permanent magnet. A permanent magnet keeps its magnetism all the time and cannot be switched off, while an electromagnet is only magnetic while current flows and loses almost all its magnetism when the current stops (because a soft iron core does not retain magnetism).
In Paper 2 this is usually asked as a state or explain question: for example, state two ways to increase the strength of an electromagnet, or explain why soft iron rather than steel is used for the core. Answer by naming the factor and its effect, e.g. more turns gives a stronger magnetic field.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)