How electricity works, in 3D

What the simulation shows

• A circuit labelled: battery, wire, switch, bulb.
• The switch closes: electrons everywhere in the wire move at once and the bulb lights.
• Zooms into the wire: electrons creeping along, bumping into the metal's atoms (which heat up); a callout: slower than a snail.
• Close on the battery: voltage is how hard it pushes.
• Close on the bulb's thin filament glowing white-hot (resistance turns electrical energy into heat and light).
• A bar magnet: field lines loop from north to south, iron filings line up, a compass needle swings round.
• A wire carrying current: circular magnetic field rings appear around it (electricity makes magnetism).
• A coil between two magnets spins when current flows: an electric motor.
• Spinning the coil between the magnets makes a current and lights a bulb: a generator.

The real numbers it runs on

The simulation is built on these facts, so the narration and the picture always agree:

• An electric current is electrons moving through a wire; a battery pushes them (that push is the voltage) round a closed loop.
• When you flip a switch, electrons all along the wire start moving at once, so the light comes on instantly; but each electron only creeps along, about a tenth of a millimetre a second.
• Electrons bump into the metal's atoms as they go; that's resistance, and it turns electrical energy into heat. A bulb's thin filament gets so hot it glows (about 2,500 °C).
• Every magnet has a north and a south pole; its field lines run from north to south and never cross. Like poles repel, opposite poles attract.
• The Earth is a giant magnet (about 50 microtesla at the surface); a compass needle lines up with its field.
• A current makes a magnetic field around its wire (Ørsted, 1820): electricity and magnetism are two sides of one force.
• A motor uses that to turn current into spinning; a generator does the reverse, turning spinning into current. Almost all the world's electricity comes from generators.

The script this video was made from

“Why the light comes on instantly”: the narration of the video above. Each highlighted moment in the simulation happens on the word that names it.

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