Send a current down a wire and a compass nearby swings: the current has wrapped itself in a magnetic field. Coil that wire up and the effect concentrates into a magnet you can switch on and off at will.
An electric current produces a magnetic field. A solenoid carrying current acts like a bar magnet whose field can be switched on and off and strengthened with more current, more turns, or a soft iron core. This is the basis of relays and loudspeakers.
A current in a wire produces a magnetic field around it. A coil (solenoid) carrying a current behaves like a bar magnet, forming an electromagnet whose field can be switched on and off.
Uses include relays (a small current switches a larger circuit) and loudspeakers.
Turn the current on and off and watch the electromagnet field appear and vanish.
Four quick checks. Each correct answer earns XP and lights this skill on your star map.
A current flowing in a wire produces...
A solenoid carrying a current behaves like...
Which change makes an electromagnet stronger?
A key advantage of an electromagnet over a permanent magnet is that it...
An electromagnet can be made stronger and put to work in switches and speakers.
An electromagnet works only while the current flows, which is exactly why it is useful: the magnetism can be switched on and off. A soft iron core boosts it because soft iron magnetises and demagnetises easily.
Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.
A relay is useful because it allows...
Reversing the direction of the current in a solenoid...
Why is soft iron, not steel, used for the core of an electromagnet?
The magnetic effect of a current is mapped. Keep the chain going.