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25 Dec 2025

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2 pages

GCSE Physics: Electromagnets and Applications

Lexi Jury

@lexi.jury

Ever wondered how your speakers blast music or how power... Show more

Physics
Electromagnetism
induced: turn into a magnet when put into a magnetic field
permanent: produce own magnetic field
magnetic fields
wh

Magnetic Fields and the Motor Effect

You've probably played with magnets before, but did you know you can create them with electricity? When current flows through a wire, it generates a magnetic field around it. Use the right-hand rule to work out the direction: point your thumb where the current goes and curl your fingers to show the field direction.

Want to make the magnetic field stronger? Simply wrap the wire into a coil or add an iron core. This clever trick is exactly how loudspeakers and electromagnets work - they can attract objects and even act as switches in circuits.

Here's where it gets really exciting: the motor effect happens when you place a current-carrying wire between magnetic poles. The magnetic fields interact and create a force that can move the wire. The force is strongest when the wire sits at 90° to the magnetic field and disappears completely when it's parallel.

Quick Tip: Remember F = BIL $force = magnetic flux density × current × length$ - this equation might pop up in your exams!

The magic happens in electric motors when this force makes a coil rotate on a spindle. A split ring commutator cleverly swaps the contacts every half turn, keeping the motor spinning in the same direction. Change the motor's direction by either reversing the power supply or flipping the magnetic poles.

Electromagnetic Induction and Generators

Here's something brilliant: you can actually create electricity just by moving a magnet! The generator effect works by inducing a potential difference in a wire that's moving relative to a magnetic field. Move a magnet in and out of a coil, and you'll generate current - it's that simple.

Keep moving that magnet back and forth, and the current direction keeps swapping, creating alternating current (AC). This is exactly how power stations generate the electricity in your home. The induced current always tries to oppose the change that created it - nature's way of maintaining balance.

Alternators spin a coil inside a magnetic field using slip rings and brushes, producing AC current. Dynamos do something similar but use a split ring commutator to keep current flowing in one direction, creating direct current (DC). You can spot the difference on an oscilloscope - AC bounces above and below the axis whilst DC stays above it.

Real-World Connection: Microphones work like loudspeakers in reverse - sound waves move a coil in a magnetic field, generating the electrical signals that become your recorded voice!

Transformers are absolute game-changers for our power grid. They use alternating current in a primary coil to create a changing magnetic field in an iron core, which induces current in a secondary coil. Need higher voltage? Use more turns on the secondary coil (step up). Need lower voltage? Use fewer turns (step down).

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Physics

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25 Dec 2025

•

2 pages

GCSE Physics: Electromagnets and Applications

Lexi Jury

@lexi.jury

Ever wondered how your speakers blast music or how power stations deliver electricity to your home? It's all down to electromagnetism - the fascinating relationship between electricity and magnetism that powers so much of our modern world.

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Magnetic Fields and the Motor Effect

Quick Tip: Remember F = BIL $force = magnetic flux density × current × length$ - this equation might pop up in your exams!

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Electromagnetic Induction and Generators

Real-World Connection: Microphones work like loudspeakers in reverse - sound waves move a coil in a magnetic field, generating the electrical signals that become your recorded voice!