How does electricity work?

Electricity is the movement of electric charge. In metals like copper, each atom gives up a few loosely bound electrons that roam freely, forming a shared sea of charge. On their own these electrons jostle randomly and go nowhere. Connect a battery or generator and it creates a voltage, a difference in electrical pressure between two points. That pressure pushes the free electrons to drift in one direction through the wire, producing an electric current. For current to flow the path must form a complete loop, a circuit, running from the source's high-potential terminal, through the wire and whatever it powers, and back to the low-potential terminal. Break the loop and the flow stops instantly. That is precisely what a switch does when you flip it off.

The engine underneath is the electromagnetic force, one of nature's four fundamental forces. Like charges repel and opposites attract, and a voltage source sets up an electric field that reaches through the entire circuit almost instantly. That field, not the electrons themselves, carries the energy. Individual electrons drift astonishingly slowly, often less than a millimeter per second, yet a lamp lights the moment you flip the switch, because the field pushes on every electron in the wire at once, at nearly the speed of light. Charge is also conserved: none is created or destroyed, so the same number of electrons that leave the source return to it. How much current flows depends on the voltage and the material's resistance, a relationship captured by Ohm's law: current equals voltage divided by resistance.

Almost all grid electricity starts as motion. In power plants, spinning turbines driven by steam, falling water, or wind rotate magnets past coils of wire, and that changing magnetic field pushes electrons, generating current. Most grids deliver it as alternating current, which cycles 50 or 60 times a second, because AC is easy to step up to high voltage for efficient long-distance transmission and step back down again with transformers. Batteries and solar panels instead produce direct current, the steady one-way flow that phones and laptops run on, which is why their chargers convert between the two. The same principles scale from a lightning bolt equalizing charge between cloud and ground to the microscopic currents inside a processor switching billions of times every second.

It is tempting to picture electrons racing through a wire at light speed, but individual electrons actually crawl; what moves near light speed is the electromagnetic field carrying the energy. Electricity is not used up as it flows, since charge is conserved and returns to the source; what an appliance genuinely consumes is energy, converting it into light, heat, or motion. A wall socket does not simply spray electricity outward, either, because nothing flows unless a device completes the circuit back to the source, which is why a bird perched on a single power line is unharmed. And people often say voltage is what kills, but it is the current passing through the body that causes harm; voltage is merely what drives that current.