Electricity and Magnetism

When you switch on a torch, electricity flows and the bulb lights up. But that only happens if the parts are joined in a complete loop.

A circuit is a path for electricity. It needs:

• a cell (often called a battery) — this pushes the electricity around,
• wires — the path the electricity travels along,
• a component to do a job, such as a bulb,
• usually a switch — to turn the circuit on and off.

Here is the golden rule: electricity only flows when the loop is complete. If there is any gap — a loose wire, an open switch, a missing part — the electricity stops and the bulb goes out.

Think of it like a running track: a runner can only keep going round if the track has no break in it. A circuit is exactly the same.

Drawing realistic pictures of cells and bulbs takes a long time and everyone draws them differently. So scientists everywhere use the same simple circuit symbols.

The symbols you need first are:

• Cell — a long thin line and a short thick line. The long line is the positive end.
• Wire — a plain straight line joining components.
• Bulb (lamp) — a circle with a cross inside.
• Switch — a small gap with a line that can close to join the loop.

A neat circuit diagram is drawn with straight lines and right-angle corners, like a tidy rectangle. Drawing circuits this way makes them easy for anyone to read.

Not every material lets electricity pass through it. We sort materials into two groups.

• A conductor lets electricity flow through it easily. Most metals — copper, iron, steel, gold — are good conductors. That is why wires are made from metal.
• An insulator does not let electricity flow through it. Plastic, rubber, wood, glass and air are insulators.

You can test a material by placing it in a gap in a circuit. If the bulb lights, the material is a conductor. If the bulb stays off, it is an insulator.

Both groups are useful. The metal inside a wire is a conductor so electricity can travel. The plastic coating around the wire is an insulator, so it is safe to hold and the electricity cannot escape.

So a single wire often contains both: a conductor to carry the electricity and an insulator to keep it where it should be.

Once you can build a simple circuit, you can change it and watch what happens.

A circuit where every component sits in a single loop, one after another, is called a series circuit.

Adding more cells: putting an extra cell in the circuit gives the electricity a bigger push. The bulb (or bulbs) become brighter.

Adding more bulbs in series: if you add a second bulb into the same single loop, the same push now has to light two bulbs. Each bulb becomes dimmer than one bulb on its own.

There is also an important effect in a series circuit: because there is only one loop, if one bulb breaks, the loop is broken and all the bulbs go out. This is why old strings of fairy lights would all go dark when a single bulb failed.

So a series circuit has a clear pattern: more cells means brighter; more bulbs means dimmer; and one break stops everything.

A magnet is a material that can attract certain other materials without even touching them.

Magnets are choosy. They only attract magnetic materials:

• iron,
• steel (which is mostly iron),
• nickel,
• cobalt.

Most materials are not magnetic. A magnet will not attract plastic, wood, paper, glass, copper, gold or aluminium. So a steel paperclip jumps to a magnet, but a plastic button does not.

A handy test: if a material is attracted to a magnet, it is a magnetic material. If nothing happens, it is not.

Be careful with one common mix-up: 'magnetic' and 'metal' are not the same thing. Many metals — copper, gold, aluminium — are not magnetic at all. Only that small group of magnetic metals is attracted.

Every magnet has two ends called poles: a north pole (N) and a south pole (S). The pulling and pushing forces are strongest at the poles.

When you bring two magnets together, there is a simple rule:

• Like poles repel — two norths push apart; two souths push apart.
• Unlike poles attract — a north and a south pull together.

The space around a magnet where it can push or pull is its magnetic field. We show the field with curved lines that travel from the north pole round to the south pole.

You can see the field for yourself by sprinkling iron filings around a magnet — they line up along the field lines. A compass also works because it has a tiny magnet inside that turns to line up with a magnetic field.

Understanding electricity and magnetism now opens up a lot of later science:

• Energy — a circuit is really a story of energy transferring from a cell to other components.
• Parallel circuits — you will study circuits with more than one loop.
• Electromagnets — electricity and magnetism are deeply linked; an electric current can make a magnet.
• Motors and generators — these machines power much of modern life and use both ideas together.
• Safe use of electricity — knowing about conductors and insulators helps you stay safe.

Whenever a topic about circuits feels tricky later, return to the golden rule: electricity needs a complete loop. And whenever magnets puzzle you, remember: like poles repel, unlike poles attract. Take your time — these clear rules will carry you a long way.