What is alternating current?
Alternating current (AC) keeps changing direction: in European homes it swings back and forth 50 times every second. Batteries give direct current (DC), which flows one way only.
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Electricity
Charges, currents and circuits — why lamps shine and phones charge.
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What it is and why it matters — intuition first, little or no math.
What are conductors and insulators?
Conductors are materials that let electricity flow through them easily, like copper and other metals. Insulators, like plastic, rubber and glass, hardly let it through at all — that is why wires are wrapped in plastic.
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What is electric charge?
Electric charge is something tiny particles carry that makes them pull or push on each other. It comes in two kinds, plus and minus: opposites pull together, and two of the same kind push apart.
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What is an electric circuit?
An electric circuit is a closed loop that electricity can flow around: from a battery, through wires and a lamp, and back to the battery. Break the loop anywhere and the flow stops.
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How does electric current work?
Electric current is a flow of tiny particles called electrons through a wire. A battery or a socket pushes them around a closed loop, and that flow makes lamps shine and motors spin.
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What is electric power?
Electric power tells how fast a device uses electrical energy. It is measured in watts (W): a kettle uses thousands of watts, a small LED lamp only a few.
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What is an electron?
An electron is a tiny particle with a minus charge that moves around the middle of every atom. When lots of electrons move along a wire together, electricity flows.
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What is electrical resistance?
Resistance is how much something holds back the flow of electricity. Long, thin wires hold it back more than short, thick ones — and the holding back turns electrical energy into heat.
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What is voltage?
Voltage is the push that makes electricity flow. A battery or a socket pushes tiny electrons through the wires — the bigger the voltage, the harder the push.
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Under the hood
How it works in detail — the mechanism step by step, with precise words.
How does electric current behave?
Electric current follows some simple rules. It needs a closed loop, it splits between paths, it warms up wires, it makes magnets, and in our homes it swings back and forth 50 times a second.
Under the hood
Numbers & formulas
How to calculate it, with formulas and worked examples.
How do we calculate electric current?
We measure current by counting how much electric charge flows past each second, in amperes. With Ohm’s law you can work it out from the voltage and the resistance, current = voltage ÷ resistance.
Numbers & formulasUnder the hood
What is Ohm’s law?
Ohm’s law is the rule that connects voltage, current and resistance: current equals voltage divided by resistance. Push harder and more current flows; make the path harder and less flows.
Numbers & formulasUnder the hood
Fun facts
Surprising facts, myths and curious questions.
Why don’t birds on power lines get shocked?
A bird sits with both feet on the same wire, so there is almost no difference in voltage between its feet and no reason for electricity to flow through it. A bird that touches two wires at once is in great danger.
Fun facts
History
Who discovered or invented it, and how it happened.
Who discovered electricity?
Nobody discovered electricity all at once. Over about 2,600 years, curious people — from the ancient Greeks rubbing amber to Volta, Faraday, Edison and Tesla — each added a piece of the puzzle.
History