1The two things in the box
A magnet's invisible reach, and a loop that carries a push
Two simple parts. A magnet that reaches out into the space around it, and a coil of wire that can carry electricity — but only when something shoves the charges along. Watch each one:
The magnet's reach
A magnet pours invisible field into the space around it. Strongest right next to it, fading as you move away. The real word is its magnetic field.
The loop & the bulb
A coil of wire lights a bulb when current flows. But current needs a push — without a push, the charges just sit there and the bulb stays dark.
2The two things you can try
Hold it still, or keep it moving
Park the magnet and freeze
Slide the magnet right into the middle of the coil — closest spot, strongest pull — and then don't move it. The field is pouring through the coil, big and steady.
Sweep the magnet in and out
Take the same magnet and slide it in and out, back and forth. Now the field through the coil is always changing — getting stronger, then weaker, then stronger again.
3Your turn — grab the magnet
Drag the magnet around the coil
Slide the magnet left and right with your finger. Watch the coil, the green push meter, and the bulb. Move it slow, move it fast, and notice exactly when the bulb cares.
4Now the real test
A strong magnet, parked dead-center 🧲
Here's the moment. The strongest magnet, pushed all the way into the coil, sitting at the closest, strongest spot — and held perfectly still. The field through the coil is huge. So… does the bulb light up?
Guess before you find out
A strong magnet sits perfectly still, right inside the coil — closest spot, strongest pull, nothing moving. Does the bulb glow?
5So is faster always better?
Each choice trades something
The faster the magnet sweeps, the faster the field changes, and the brighter the bulb glows. Real generators spin magnets past coils to make electricity this way.
A parked magnet costs zero effort. You can leave it forever and never get tired.
A magnet makes electricity only while it's moving near a coil. It's the change in the field that pushes the current — a still magnet, however strong, does nothing.
Psst, grown-ups: this is Faraday's law of induction. The voltage (EMF) induced in a coil equals minus the rate of change of magnetic flux through it: EMF = −N·dΦ/dt. A stationary magnet gives a steady flux, so dΦ/dt = 0 and no current flows; moving it changes the flux and drives current, and faster motion or more turns means a bigger EMF. The minus sign is Lenz's law — the induced current opposes the change, which is why you feel the magnet resist and why generating electricity always takes work. Every power-plant generator is this exact trick scaled up: magnets and coils spun past each other.