Guided lesson

Electromagnetic Induction

6.15

3 guided lessons · 27 checks · 6. Magnetism and Electromagnetism → Electromagnetic Induction

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Making voltage from motion

Induction is the motor effect run backwards: move a conductor through a magnetic field — or move the field past the conductor — and a voltage appears across the conductor. No battery is needed; the motion itself is the source, and the faster or stronger the arrangement, the bigger the induced voltage.

What you know already

Motion makes electricity: sweep a wire across field lines or thread a changing field through a coil, and a voltage appears without any battery. This note covers both induction triggers, the meter-kick diagrams, and the three size factors — speed, field strength and turns.

Key points of understanding

A voltage is induced in a conductor when it moves through a magnetic field.
A voltage is also induced when the magnetic field through a conductor changes.
The induced voltage grows with the speed of the movement.
A stronger magnetic field induces a larger voltage.
No relative change between conductor and field means no induced voltage.

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1.Making voltage from motion

6.15

Key points

A voltage is induced in a conductor when it moves through a magnetic field.
A voltage is also induced when the magnetic field through a conductor changes.
The induced voltage grows with the speed of the movement.
A stronger magnetic field induces a larger voltage.
No relative change between conductor and field means no induced voltage.

First pass

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2.Reading the induction diagrams

6.15

The diagram of a wire sweeping through a horseshoe field tells the whole story: the wire cuts the lines, the meter needle kicks, and the kick's direction follows the sweep direction. Reverse the sweep and the needle kicks the other way — polarity tracks the motion.

Electromagnetic induction diagram: a wire conductor sweeping through the magnetic field between two magnet poles, with an induced voltage shown across it — Moving an electrical conductor in a magnetic field to induce a potential difference

3.Coils, factors, and bigger induced voltages

6.15

Replace the single wire with a coil and every turn cuts the field, so the induced voltages add — more turns, bigger voltage. The full factor list for the induced potential difference is the exam's favourite: speed of movement, magnetic field strength, and the number of turns.

coil-induction, IGCSE & GCSE Physics revision notes — When the magnet enters the coil, the field lines cut through the turns, inducing a potential difference