How does electricity work? The short answer
Everything is made of atoms, and atoms contain tiny particles called electrons that carry a negative charge.1 In metals such as copper, some electrons are only loosely held, so they can move from atom to atom.16 Electricity is the flow of those charges.110
To get a steady flow you need three things: something that pushes (a battery, a generator or a wall socket), a path for the charge (a wire), and a complete loop, called a circuit.17 Put a device such as a light bulb in the loop and the moving charge delivers energy to it. A switch simply opens a gap in the loop to stop the flow, or closes it to start it again.1
What is electricity made of?
Electricity isn't a substance you can pour. It's the movement of electric charge. An atom has a nucleus of positive protons and neutral neutrons, with negative electrons around it. Normally the charges balance.1 The electrons closest to the nucleus are held tightly, but in some materials the outer ones are loose. In a metal they form a kind of "sea" of free electrons that can drift through the whole wire.6
- Conductors (copper, aluminium and other metals) have lots of free electrons, so charge flows easily.16
- Insulators have almost no free electrons, so they block the flow. That is why wires are wrapped in an insulating coating.6
When the charges sit still and build up, you get static electricity: the zap from a doorknob after you walk across a carpet, or hair standing up after you rub a balloon on it.113 When they move steadily around a loop, you get an electric current, which is what powers your home.10
How a circuit works: the battery is a pump
A battery holds two different metals in a chemical paste called an electrolyte. A chemical reaction makes one end release more electrons than the other, so one end becomes negative (−) and the other positive (+).1 Join the two ends with a wire and electrons flow out of the negative end, through the wire and the bulb, and back into the positive end.1
Here's the key idea: the battery doesn't make electrons. They were already in the wire. The battery is more like a pump that keeps them moving around the loop. The bulb doesn't use up electrons either. Every one of them comes back. What the bulb uses is energy, which it turns into light and heat.16
Voltage, current and resistance: the water-pipe picture
An easy way to picture a circuit is water flowing around a closed loop of pipe, with a pump.
The three are linked by Ohm's law: more push gives more flow, and more resistance gives less. Voltage is the cause and current is the effect.7
current = voltage ÷ resistance or I = V ÷ R
For example, double the resistance and the current is cut in half.7 Like every analogy, the water picture isn't perfect, but it gets the relationships right.
Why does a light bulb glow?
As electrons move through a wire, they keep colliding with the metal's atoms. Each bump hands energy to the atoms, so the wire warms up.6 In an old-style (incandescent) bulb, the filament is a very thin wire with lots of resistance. It gets so hot that it glows.7 Other kinds of bulbs make light in different ways, but the circuit around them works just the same.
How fast does electricity travel?
This is the puzzle at the heart of the video. When you flip a switch, the light comes on instantly. Yet each electron in the wire drifts along at only about 0.1 millimetres per second (10−4 m/s).6 On its own, a single electron would take hours to cross a room.
The answer is that the wire is already full of free electrons. When the battery pushes charge in at one end, those charges push the ones ahead of them, which push the next, and so on down the line, like a tube packed with marbles. The push, a change in the electric field, races along the wire at around 108 metres per second, a big fraction of the speed of light.6 Light itself travels at exactly 299,792,458 metres per second.15 So the electrons already sitting in the bulb start moving almost at the moment you close the switch.
Where does electricity come from?
Electricity is called a secondary energy source, or energy carrier: we make it by converting other energy sources, such as natural gas, coal, nuclear fuel, wind, flowing water and sunlight.2 Almost all of it is made with generators.
How a generator makes electricity
In 1831 Michael Faraday discovered that moving a magnet inside a coil of wire makes an electric current flow in the wire. He used the idea to build the first generator.311 Most of the world's electricity still comes from generators that work on this principle: a spinning magnet (usually an electromagnet) turns inside coils of copper wire, pushing the electrons in the coils along.3
The only difference between power plants is what does the spinning. In most, a moving fluid pushes the blades of a turbine, which turns the generator:3
- Steam: fuel is burned (natural gas or coal), or nuclear fuel is split, to boil water. The steam spins the turbine. (See how nuclear energy works.)3
- Hydropower: water falling through a dam spins the turbine.3
- Wind: the wind turns the blades of a wind turbine.3
Solar panels are the big exception. Their photovoltaic (PV) cells absorb sunlight, and that energy gets charges moving in the cell, with no moving parts at all.314
What makes America's electricity?
In 2023, U.S. power plants generated about 4,178 billion kilowatthours of electricity.5
Source: U.S. Energy Information Administration.5 Overall, about 60% came from fossil fuels, 19% from nuclear and 21% from renewables.5
How electricity gets to your home
From the power plant, electricity travels on high-voltage transmission lines, the cables strung between tall metal towers. High voltage makes long-distance transmission more efficient and less expensive. Near towns, transformers at substations step the voltage down, and lower-voltage distribution lines carry it to homes, where it's safer to use.41 In the U.S., wall sockets supply 120 volts of alternating current (AC); most of the rest of the world uses about 240 volts.18
Series and parallel circuits
There are two basic ways to connect two bulbs to one battery:
- Series: both bulbs sit one after the other in a single loop. The same current has to pass through each one, and their resistances add up, so less current flows and both glow dimmer. If one breaks or is switched off, the whole loop stops.810
- Parallel: each bulb has its own path to the battery. Each gets the full voltage and works independently, so both shine brightly and one can be switched off while the other stays on.810
Houses and cars are wired in parallel, which is why switching off the kitchen light doesn't turn off the TV.8
How was electricity discovered?
Nobody invented electricity; it's part of nature. Scientists have been working out how it behaves since the 1600s.2 A few big moments:
- 1700s: Benjamin Franklin's kite-and-key experiment showed that lightning is electricity. He also suggested lightning rods to protect buildings.16
- 1800: Alessandro Volta announced the first electric battery, the "voltaic pile", the first source of a steady current.12
- 1831: Michael Faraday discovered that a moving magnet makes current flow in a wire, and built the first generator.11
- 1882: Thomas Edison, who made the first long-lasting incandescent bulb, opened the Pearl Street power station in New York City, which served 85 customers.217
- Late 1800s: Nikola Tesla pioneered alternating current (AC), which made it cheaper to send electricity over long distances and brought it into homes and factories.2
Electrical safety
A toy circuit with one or two small AA batteries is safe to build with an adult. Mains electricity from wall sockets is never safe to play with. Electricity has two main hazards: shocks, when current passes through a person (ranging from painful to heart-stopping), and heat, when too much current overheats wires and starts fires.9 Contact with power lines is one of the most common causes of serious electrical injuries.19
- Never poke anything into a wall socket or open up a plugged-in device.
- Stay far away from fallen or low-hanging power lines, and tell an adult or call for help.19
- Don't overload outlets: plug only one heat-producing appliance (like a heater or toaster) into an outlet at a time.20
- Tell an adult if an outlet feels warm, sparks, or a cord is damaged.20
Common misconceptions
"Electrons race through the wire at the speed of light." Each electron only drifts about 0.1 mm per second. It's the
push that travels near light speed.
6
"Batteries and power plants make electrons." The electrons are already in the wire. The source only pushes them around the loop.
1
"A bulb uses up electricity like a car uses fuel." Every electron returns to the source. The bulb uses the
energy they carry and turns it into light and heat.
16
"Electricity is an energy source, like coal." It's an energy carrier: it has to be made from another source first.
2
"Current flows from + to −, so electrons do too." That "conventional current" direction dates back to Benjamin Franklin. In metal wires, the electrons actually move from − to +.
6
FAQ
How does electricity work, explained simply?
Wires are full of electrons that can move. A battery or generator pushes on them, and if there is a complete loop (a circuit), they flow around it. Devices like bulbs sit in the loop and turn that flow's energy into light, heat or motion. Open a switch and the loop is broken, so the flow stops.
Where does electricity come from?
Most of it is made in power plants by generators: a turbine spins a magnet inside coils of copper wire, which pushes electrons along. Falling water, wind, or steam (from burning natural gas or coal, or from nuclear fuel) spins the turbine. Solar panels are the main exception: sunlight makes electrons flow directly, with no spinning parts.
Can electricity be man-made?
Yes and no. Electricity is a natural thing: lightning and static shocks are electricity. But the electricity in your home is produced by people, who convert other energy sources such as natural gas, nuclear fuel, wind, water or sunlight into electrical energy. That's why the EIA calls electricity a secondary energy source.
What are the three rules of electricity?
People often mean the three quantities in Ohm's law: voltage (the push), current (the flow) and resistance (anything that slows the flow). They're linked by current = voltage ÷ resistance. Also remember that current needs a complete loop to flow.
How fast does electricity travel?
The push travels through a wire at a large fraction of the speed of light, which is why a lamp turns on instantly. But each electron only drifts slowly, typically around a tenth of a millimetre per second, because it keeps bumping into atoms.
How was electricity discovered?
No one person discovered it. Benjamin Franklin showed in the 1700s that lightning is electricity. Alessandro Volta built the first battery in 1800. In 1831 Michael Faraday found that moving a magnet in a coil of wire makes electricity flow, the idea behind almost every power plant today. Edison and Tesla then helped bring electric light and power into homes.
Could we ever run out of electricity?
Electricity itself isn't a fuel that runs out; it has to be made from other energy sources. Some of those, like coal and natural gas, are limited. Others, like wind, sunlight and flowing water, are renewable. In 2023 about 21% of U.S. electricity came from renewables.
Sources
- U.S. EIA Energy Kids, Science of electricity (atoms, batteries, circuits, magnets, transformers)
- U.S. EIA Energy Kids, Electricity basics
- U.S. EIA Energy Explained, How electricity is generated
- U.S. EIA Energy Explained, How electricity is delivered to consumers
- U.S. EIA FAQ, What is U.S. electricity generation by energy source?
- OpenStax College Physics 2e, 20.1 Current (drift velocity, signal speed)
- OpenStax College Physics 2e, 20.2 Ohm's Law: Resistance and Simple Circuits
- OpenStax College Physics 2e, 21.1 Resistors in Series and Parallel
- OpenStax College Physics 2e, 20.6 Electric Hazards and the Human Body
- Encyclopaedia Britannica, How Does Electricity Work?
- U.S. EIA Energy Kids, Famous people: Michael Faraday
- Encyclopaedia Britannica, Alessandro Volta
- Encyclopaedia Britannica, Static electricity
- U.S. Department of Energy, Solar Energy Technologies Office: How Does Solar Work?
- NIST, Definitions of the SI base units (speed of light)
- U.S. EIA Energy Kids, Famous people: Benjamin Franklin
- U.S. EIA Energy Kids, Famous people: Thomas Edison
- OpenStax College Physics 2e, 20.5 Alternating Current versus Direct Current
- OSHA, Electrical incidents: hazard recognition
- NFPA, Electrical fire safety