Electricity
Where does the electricity in the socket come from, and where does it go when we use it?
Electricity is not a substance but a way of carrying energy: a push on the electrons inside wires. Most of that energy comes, one way or another, from the Sun or from uranium made in dying stars; when we use it, it ends up as heat that spreads away.
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In numbers
- ≈ 8 cm/hourelectron drift speed (1 A, 2 mm copper wire)
In five stops
Where were its atoms born?
The electrons that carry electricity are already inside the copper atoms of the wires; no electrons travel to your home from the power station. Electrons have existed since the first second of the universe. What changes is the source of the energy that pushes them.
How did nature prepare it?
Most of this energy comes from the Sun one way or another: solar panels use its light directly, wind turbines use the movement of air the Sun has heated, and dams use water the Sun evaporated and rained down on high ground. Coal and natural gas are sunlight captured by plants and plankton millions of years ago. The uranium in nuclear power stations formed in dying stars and neutron-star collisions; geothermal plants use Earth's internal heat.
What did people do?
Most power stations turn a turbine: steam, water or wind spins it, and the turbine drives a generator. In the generator, magnets and coils of wire turn past each other and the changing magnetic field pushes the electrons in the wires; this is called electromagnetic induction. Solar panels instead use light to set electrons moving directly. Electricity is carried to cities by high-voltage lines.
What happens when we use it?
When you switch on a lamp the energy spreads through the wires very fast, but the electrons themselves creep along: in a 2-millimetre copper wire carrying 1 ampere, about 8 centimetres an hour. With the alternating current at home, the electrons just jiggle back and forth. The energy becomes light in a lamp, chemical energy in a charging battery, and motion in a motor.
Where does it go next?
Almost all the electrical energy we use ends up as heat: a lamp's light hits the walls and warms them, a phone's processor gets warm. That heat spreads into the air and from there into space as infrared radiation. The energy doesn't disappear, but it spreads out too thinly to be used again.
Did you know?
When you switch on a lamp, the electrons in the wires move more slowly than a snail. What's fast is not the electrons but the electric field that pushes them, spreading along the wire.
Related:What is inside a phone battery, where did it come from, and where does it go? →How did copper become humanity's first metal? →How did coal form? →
Sources for this page
- Electricity generation (opens in a new tab)
- Electric current (opens in a new tab)
- Drift velocity (opens in a new tab)
- GW170817 (neutron star merger) (opens in a new tab)