You can induce a current (or voltage) in a CONDUCTOR by having it in the region of a CHANGING MAGNETIC FIELD.
- For example, you can INDUCE a current in a wire by moving part of a loop of wire up (or down) through a magnetic field.
If you change the direction you are moving the wire in or change the direction of the magnetic field, you change the DIRECTION of the current, whereas if you use stronger magnets, loop the wire more times, use move the wire (or magnet, as this produces the same result) faster, you change the SIZE of the current.
An electromagnet is a coil of wire, often coiled around a soft iron core (the soft iron core allows the current to be reversed quickly), which is made into a magnet when a current is run through it. As these become magnets when a current is running through the wire, when the current is switched off, electromagnets are no longer magnetic.
The ability to switch electromagnets can be useful in places such as scrapyards, where control over which metal (iron, nickle, cobalt and steel are magnetic metals) objects need to be moved. If a permanent magnet was used, any magnetic object within the magnet's magnetic field would be attracted, as they cannot be switched off.
As previously mentioned, you can increase the strength of an electromagnet by coiling the wire more times, using the soft iron core and increasing the current running through the wire, you will have to know this in I/GCSE Physics.
Drafted by Catrina (Physics)