Electromagnetic induction — Physical education, 14–17 years
A changing magnetic field can create a voltage in a wire. Physical education, 14–17 years.
Magnetism making electricity
Move a magnet near a coil of wire, and the magnetic field through the coil changes. That change creates a voltage, which can drive a current if the circuit is complete. A still magnet beside a still coil produces no induced voltage.
Why induction matters
Batteries are useful, but they store a limited amount of chemical energy. Scientists wanted a way to generate electricity continuously from motion. Faraday’s discovery showed that changing magnetism could turn mechanical motion into electrical energy, linking generators and motors.
Moving a magnet through a coil
Connect a coil to a galvanometer and push the north pole of a magnet into it. Step 1: the magnetic field through the coil increases. Step 2: the meter deflects, showing an induced current. Step 3: hold the magnet still and the reading returns to zero. Pull it out and the deflection reverses.
The magnet-alone trap
It is easy to think that any magnet near a wire must produce electricity, because magnets clearly affect some objects. Induction depends on a changing magnetic field through the circuit, not merely on the presence of a magnet. Faster movement usually produces a larger voltage.
Generators and wireless charging
In a power-station generator, turbines turn magnets or coils, continually changing the magnetic field and producing alternating voltage. Wireless phone chargers use changing currents in one coil to create a changing field, which induces a voltage in a nearby coil. Both rely on the same idea.
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