Electronics
What is electricity?
Electricity is electric charge on the move. In a wire, the moving charges are electrons drifting through the metal. A battery pushes them round a closed loop, called a circuit, and the parts on the way turn the energy they carry into light, heat or motion.
Charge, the thing that moves
Everything is made of atoms. Inside each one are protons, with a + charge, and electrons, with a − charge. Opposite charges pull together and like charges push apart.
Charge is measured in coulombs (C). One electron carries about 1.6 × 10⁻¹⁹ C, so a single coulomb is roughly six billion billion electrons.
Live experiment
Close the loop
A battery, a loop of wire, a switch and Pip, an LED. Flip the switch to close the loop and watch the charge move and Pip light up. Open it and everything stops.
“What is electricity?” is lesson 1 of 6 in Copper Flats, Electronics World 1. No account needed: start playing now.
Conductors and insulators
In metals like copper, some electrons aren't tied to any one atom. They can drift from atom to atom, so metals are conductors. In plastic, rubber and glass the electrons are held tight, so those are insulators.
That's why a wire is a copper core in a plastic coat: the copper carries the current and the plastic keeps it where it belongs.
It has to go all the way round
Charge only keeps flowing round a complete loop: out of the battery, through the parts and back. Break the loop anywhere and the current stops everywhere, not just near the gap. A switch is simply a neat way to open and close that gap.
Energy goes round with the charge
A circuit doesn't use up charge. The same charge goes round and round. The battery gives it energy, and the parts take that energy away: an LED turns it into light, a resistor into heat.
The electrons themselves drift surprisingly slowly, often less than a millimetre per second. A light still comes on the instant you flip the switch, because charges all round the loop start moving at practically the same moment.
Two numbers describe what's happening. Voltage is the push the battery gives each bit of charge, and current is how much charge flows past a point each second.
Free lesson
Now build it yourself
Each lesson comes in three short parts: see the idea, try it on a live board, then build it yourself, with quick checks as you go.
“What is electricity?” is lesson 1 of 6 in Copper Flats, Electronics World 1. No account needed: start playing now.
Work it out
Practice questions
Three quick questions from the lessons. Pick an answer to check it.
Show the answer
Answer: Copper. Copper is a metal, and in metals some charge is free to move. That's why wires have a copper core. Rubber, glass and plastic hold their charge tight.
- Why not “Glass”? Glass holds its charge tightly, so it's an insulator. It's been used on power lines to keep the current in the wire.
- Why not “Rubber”? Rubber is an insulator: it holds its charge tight. That's why wires are often wrapped in it.
- Why not “Plastic”? Plastic is an insulator, which is why it coats wires and covers plugs. Charge can't move through it easily.
Show the answer
Answer: It goes out. Charge needs a complete loop. One gap anywhere stops the flow everywhere, however far it is from the LED.
- Why not “It stays on”? A circuit has to be a complete loop. A gap anywhere stops the flow everywhere, however far it is from the LED.
- Why not “It gets a bit dimmer”? A cut doesn't add a little resistance: it breaks the loop. With no path back to the battery, no current flows at all.
Show the answer
Answer: No, the same charges go round and round; the battery hands out energy. Charges aren't consumed. They circulate around the loop, and the battery gives them energy, which parts like LEDs turn into light and heat.
- Why not “Only when the circuit is switched off”? Switched off, nothing flows, so nothing could be used up anyway. On or off, the charges themselves are never consumed.
- Why not “Yes, the LED eats them”? The LED doesn't eat charge. It turns the energy the charge carries into light and heat, and the charge flows on round the loop.
“What is electricity?” is lesson 1 of 6 in Copper Flats, Electronics World 1. No account needed: start playing now.
Questions people ask
What is electricity in simple terms?
Electricity is electric charge on the move. In a wire, tiny negative particles called electrons drift through the metal. A battery gives them energy, and the parts in the circuit turn that energy into light, heat or motion.
Why does a circuit need to be a closed loop?
Charge can only keep flowing if it has a complete path out of the battery, through the parts and back again. Break the loop anywhere, with a switch or a cut wire, and the current stops everywhere at once.
Does a circuit use up electricity?
It doesn't use up charge. The same charge goes round and round the loop. What gets used is energy: the battery gives energy to the charge, and parts like an LED or a heater take it and turn it into light or heat.
What is the difference between a conductor and an insulator?
A conductor, like copper, has charges that are free to move, so current flows through it easily. An insulator, like plastic, rubber or glass, holds its charges tightly, so almost no current flows. A wire is a copper conductor inside an insulating coat.
Related topics
- What is electric current?How much charge flows past a point each second, in amps, and why it's the same all round a loop.
- What is voltage?The push that makes charge flow: what a volt is, and why stacked cells add up.
- Ohm's law explainedV = I × R: set any two of voltage, current and resistance and the third follows.