Key Stage 2 design and technology · Technical knowledge

KS2 series circuits in design and technology: a guide

In Key Stage 2 design and technology, children learn to understand and use electrical systems in their products, such as a series circuit with a switch, a bulb, a buzzer or a motor. They design a circuit to do a job, build it into a model, test it and fix faults. This is different from the science lessons on electricity, because the circuit has to be part of something that works and looks right.

Series circuits in products, explained

The national curriculum says that pupils should understand and use electrical systems in their products, with series circuits incorporating switches, bulbs, buzzers and motors as examples. Those examples are non-statutory, so schools choose which components to use, but a battery, wires, a switch and one or two outputs is the usual starting point. A series circuit is a single loop. The battery pushes electricity around the loop through each component in turn, and every component is part of the same path.

That single loop explains how series circuits behave. If any part of the loop is broken, such as an open switch, a loose wire or a blown bulb, everything stops. A switch can go anywhere in the loop and still control the whole circuit. If you add more bulbs in the same loop, they all share the energy from the battery, so each is dimmer. Adding another cell, which gives a stronger push, makes bulbs brighter, a buzzer louder and a motor faster. A battery is two or more cells joined together, although in everyday speech people call a single cell a battery as well.

In design and technology the circuit is a part of a product with a job to do, such as a torch, a model lighthouse, a buggy, a fan or an alarm. Children draw the circuit with standard symbols, plan where the switch will go so that it can be reached easily, and decide how to hold the parts in place. Materials matter. Metals conduct electricity, so they are used for wires and contacts. Plastic, card and rubber are insulators, so they are used for casings and for covering connections. Some components also have to be connected the right way round: an LED, and most of the buzzers used in schools, will only work one way, while a motor will spin in the opposite direction if its wires are swapped, which can be useful or a problem depending on the design.

Testing and fault-finding are a large part of the learning. When a circuit does not work, children are taught to be systematic rather than guess: check the battery, check each connection in turn, check the bulb is tight in its holder, check any component with a direction is the right way round, and test each component by itself with the battery. This is the same approach that electricians and engineers use, and it builds patience and clear thinking.

The second objective for this topic asks pupils to apply their understanding of computing to program, monitor and control their products. A simple switch is the easiest way to control a circuit, but a sensor and a small programmable control board can do the same job automatically, for example switching on a light when a room gets dark. That idea is covered in a separate topic, but it is helpful to know that the circuits children build now are the foundation for those programmable products. All work in school uses low-voltage batteries and never mains electricity.

Words your child will hear

Series circuit: A circuit with a single loop, where all the components are joined one after another.
Cell: A single source of electrical energy. Two or more cells joined together make a battery.
Component: Any part of a circuit, such as a bulb, buzzer, motor or switch.
Switch: A component that opens or closes the circuit, to turn it off or on.
Conductor: A material that lets electricity pass through it easily, such as most metals.
Insulator: A material that does not let electricity pass through it, such as plastic or rubber.
Circuit symbol: A standard drawing used to show a component in a circuit diagram.

What the National Curriculum says

The programme of study for Key Stage 2 says:

When designing and making, pupils should be taught to understand and use electrical systems in their products [for example, series circuits incorporating switches, bulbs, buzzers and motors]
When designing and making, pupils should be taught to apply their understanding of computing to program, monitor and control their products

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

Try it: a lighthouse with a working light

Design a series circuit for a model lighthouse, where a switch at the base turns on a bulb at the top. Predict what happens when the switch is pressed, and what changes if a second bulb is added to the same loop.

List the components. You need two 1.5 V cells in a holder (3 V in total), a push switch, a bulb in a holder and enough wires or crocodile clips to join them, long enough to reach from the base to the top of the tower.
Plan the loop. In a series circuit everything is joined in one line and back to the start, so the path runs from one end of the cells, through the switch, up to the bulb and back down to the other end of the cells. Draw it with circuit symbols before building.
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cells > switch > bulb > cells
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Predict. With the switch open, the loop is broken and the bulb stays off. Pressing the switch closes the loop and the bulb lights. Because it is one loop, it does not matter whether the switch goes before or after the bulb.
Add a second bulb to the same loop. Now both bulbs share the energy from the cells, so both will be dimmer than the single bulb was. If one bulb is unscrewed, the loop breaks and the other goes out too. For a lighthouse, one bright bulb may suit the design better than two dim ones.
Find a fault, if there is one. Nothing lights? Work through the circuit in order rather than guessing. Check the cells are fresh and sit firmly in the holder, then check each join, then check the bulb is screwed in. Finally, test the bulb by connecting it straight to the cells on its own.

The circuit is a single loop of cells, switch and bulb. Closing the switch lights the bulb, and any break in the loop turns it off. Adding a second bulb in the same loop makes both dimmer. Faults are found by checking the cells, then every join, then each component on its own.

Common mistakes and how to help

Thinking one wire from the battery to the bulb is enough

Children often imagine that electricity travels from the battery to the bulb and gets used up there, so one wire seems sufficient.

What helps: A bulb has two connections for a reason. Build the circuit as a complete loop and show that removing either wire turns the bulb off.

Believing the bulb nearest the battery is brightest because electricity is used up on the way round

The idea of electricity being “used up” is very common and understandable.

What helps: Make a loop with two identical bulbs and swap their order. They are equally bright, because the same current flows through all the parts of a series circuit.

Expecting more bulbs to give more light

In daily life, more lamps make a room brighter, so children expect the same in a circuit.

What helps: Add a second bulb in the same loop and watch both become dimmer. Then add another cell and see them brighten. This shows that the battery’s energy is shared.

Assuming components work whichever way round they are connected

Wires and bulbs do work either way, so children assume everything else does too.

What helps: Try a buzzer on its own, one way and then the other. Look for the red wire or the plus sign, and connect it towards the positive end. Swapping a motor’s wires makes it spin the other way, which is a useful thing to know.

How to help at home

Build a basic circuit. A battery holder, a bulb in a holder and some wires, from a cheap kit or a toy shop, is all you need. Use only AA or AAA cells. Never use mains electricity, never join the two ends of a battery with just a wire (it gets hot and runs the battery down), and keep button or coin cells away from young children because they are dangerous if swallowed.
Test conductors and insulators. Add a gap to a working circuit and place everyday objects across it: a spoon, foil, a key, a plastic lid, a rubber band, a pencil lead. Before testing, ask your child to predict which will let the bulb light, then record the results.
Make a switch. On a piece of card, push a metal paper clip onto a paper fastener so that it can swing to touch a second fastener, and join a wire to each fastener. Ask your child to explain what happens to the loop when the clip touches and when it swings away.
Be a fault finder. Build a working circuit, then without your child watching, loosen one join, unscrew the bulb slightly or turn one of the two cells the wrong way round in its holder. Let them work out the cause by testing each part in turn. Agree a rule to check the simplest things first.
Spot the switch. Look at a torch, a doorbell, a bicycle light or a toy and ask where the switch is, what it controls, and what the other parts of the circuit are. Do not take apart anything that is plugged in, and be careful with any batteries.

Builds on

Key Stage 1: Strong, stiff, stable structures
Key Stage 1: Levers and sliders
Key Stage 1: Wheels and axles

Leads on to

Key Stage 3: Properties of materials
Key Stage 3: Beams, frames and forces
Key Stage 3: Gears, levers and mechanisms
Key Stage 3: Electronic circuits and systems
Key Stage 3: Sensors, actuators and microcontrollers