Electricity

Electricity

Leaping bolts of lightning are fueled by electrons. These tiny charged particles that whiz around inside atoms are about the smallest things we can imagine. Yet everything electric is ultimately driven by them.

From heating and lighting our homes to powering trains, electricity can do a remarkable range of things. When electrons march through wires, they carry energy from place to place, making what we call an electric current. Electric currents power everything that plugs into a socket at home and, through batteries, fuel cell phones and laptops when we are on the move. When electrons build up in one place, they make static electricity. It's static electricity that crackles when you take off your sweatshirt - and static buildup that causes lightning bolts to zap back to Earth.

What happens when a current flows?

When you plug a lamp into an outlet or turn on a light switch, electrical energy flows along the wire. The atoms in the wire stay put, while electrons flow all around them, each one carrying a tiny amount of electricity called a charge. Although each electron moves slowly, the wire is packed with them. That's why electricity takes no time at all to flow from its source to where it is used. The lamp lights instantly.

Current flowing

When the power is switched on, electrons that are already inside the wire start to move. The bigger the voltage, the more electrons are pushed through the wire and the bigger the electric current.

No current flowing

When you switch off the power, there's nothing to push the electrons along in the same direction. They stop flowing in a current and dance around more randomly.

How a battery works

Batteries are portable power supplies that make electricity using chemistry. They have a negative terminal (the metal case and plate at the bottom), a positive terminal (the metal knob on top), and an electrolyte (chemical mixture) in between. When you connect a battery into a circuit, chemical reactions start up inside it, generating electrons and positive ions (atoms missing electrons). The positive ions drift through the inside of the battery. The electrons flow around the circuit outside, powering whatever the battery is connected to.

Battery

The simplest batteries have a negative terminal made from zinc and a positive terminal made from carbon (graphite) and can only be used once before being thrown away. Rechargeable batteries use materials that allow reversible chemical reactions inside them and so can be reused hundreds of times.

Electric circuits

The path that electrons flow along is called a circuit. An electric circuit carries energy from a power source (such as a battery) to something that uses power (such as a lamp) and back again. Electricity only flows if a circuit forms a complete (closed) loop. If the loop is broken somewhere along the line, electrons can’t get across the gap and the electric current stops flowing. Switches work by breaking circuits in this way.

Series circuit

The entire electric current flows through each part of the circuit in turn. Exactly the same current flows through each lamp.

Parallel circuit

The electric current has to split to flow through different parts of the circuit. Only half the current flows through each lamp.

Static electricity

We usually think of electricity as flowing through something, but when electrons build up with no circuit for them to flow along they create static electricity. Static electricity is what makes your hair stand on end when you pull on a polyester T-shirt, or a balloon stick to the wall after you have rubbed it on your sweatshirt. The surfaces of things like balloons steal electrons from other surfaces and the extra electrons make them negatively charged.

Negative charge

If you rub a balloon on your sweatshirt, the balloon develops a negative charge. If you hold the balloon up to a wall, it pushes away negative electrons and makes the wall's surface positive. The balloon sticks in place.

Unlike charges attract: Negative and positive charges attract, so the balloon sticks to the wall.

Repulsion

When you rub two balloons on your sweatshirt, one after another, they both become negatively charged. If you try to hold the balloons together, their negative charges push apart.

Like charges repel: Two negative charges repel each other, so the balloons push apart.