How Electricity Works: Explained for Kids
Here is the question that catches most adults out. Electrons in a wire drift along at roughly the speed of a snail - centimetres per minute. So why does the bulb light the instant you flip the switch, rather than several minutes later?
The answer is the most useful thing a child can learn about electricity, and it makes almost everything else fall into place.
The wire is already full
The electrons do not travel from the switch to the bulb. They are already there, everywhere in the wire, all the way round, before you touch anything. Copper is packed with loose electrons sitting still.
Flipping the switch does not send electrons on a journey. It gives every electron in the whole loop a push at once, and they all shuffle forward together. The one already sitting in the bulb starts moving immediately.
The standard image is a tube already full of marbles. Push one in at your end and one pops out the far end instantly - not because your marble travelled the length of the tube, but because the tube was full. Electricity is that, and the electrons genuinely do crawl.
A circuit only works as a complete ring
This is the second big idea, and it is why "the wire came out" is the answer to most broken electrical things.
Electrons have to be able to go all the way round and back to where they started. One gap anywhere - a flipped switch, a cut wire, a bulb unscrewed from its socket - and nothing moves anywhere in the loop. Not slowly. Not partially. Everything stops at once, because a queue that cannot advance at the front cannot advance anywhere.
An open switch is just a deliberate gap. That is all a switch is: a gap you can open and close on purpose.
The three quantities, in plain words
Textbooks give these as formulae before children have any feel for them. The feel comes first.
| Word | What it actually means | Water version |
|---|---|---|
| Voltage | How hard the electrons are being pushed | Water pressure |
| Current | How many electrons flow past per second | How much water flows |
| Resistance | How hard the path is to get through | A narrow pipe |
The relationship is the intuitive one: push harder and more flows; make the path harder and less flows. In the simulation above there are dials for the battery push and the resistance, and turning them shows exactly that - more push, more current; more resistance, less current. That is Ohm's law, arrived at by feel rather than by memorising a triangle.
What a short circuit is, and why it is dangerous
A short circuit is an easy path that skips the thing the electricity was supposed to be doing.
If you connect a bare wire straight across the battery, bypassing the bulb, you have removed almost all the resistance from the loop. Very little resistance means a very large current. Large current in a thin wire means heat, and that is why a short circuit makes things hot, melts insulation and starts fires.
This is worth doing in a simulation rather than at the kitchen table, and it is the button children reach for first.
Answering "which way does it actually go?"
Confusing, and better addressed than dodged.
Electrons carry a negative charge, so they physically move from the negative terminal round to the positive one. But conventional current - the arrows in every textbook - is drawn from positive to negative, because the convention was fixed before anyone knew electrons existed.
Both are used. Nothing breaks, because the maths works either way. If a child notices the contradiction, they have spotted something real, and the honest answer is that we got the direction backwards early and never renamed it.
Where 3Eyes Fits
The circuit lesson above is one of about sixty interactive science lessons built into 3Eyes, a parental controls product for family computers - it filters the machine, approves sites rather than blocking them individually, and restricts YouTube to channels you choose.
They are there because a computer that only ever refuses things is a hard sell to a child. With sixty science lessons and a tutor on the same laptop, the limits are no longer the whole story.
About two minutes to set up. See what it includes or create an account.
Frequently asked questions
Why does the light come on instantly if electrons move slowly? Because the wire is already full of electrons everywhere along it. Closing the switch pushes all of them at once, so the ones already at the bulb move immediately. Nothing has to travel there first.
What is a circuit? A complete loop that electrons can travel all the way around. Break it anywhere and everything stops everywhere, because the queue cannot move.
What is the difference between voltage and current? Voltage is how hard the electrons are pushed; current is how many actually flow past per second. Pressure versus amount, in water terms.
Why is a short circuit dangerous? It gives the electricity a path with almost no resistance, so a very large current flows. That current turns into heat in the wire, which melts insulation and can start a fire.
Do electrons really go from negative to positive? Yes. The arrows in textbooks point the other way because the convention was set before electrons were discovered, and it was never changed.