A switch is a device that is used to OPEN or to CLOSE a circuit. Many simple switches, are made from two pieces of conductive material (for example; metal), that made to touch to CLOSE the switch (to turn the circuit ON), and pulled apart to make the switch OPEN (to turn the circuit OFF).

• When a circuit is OPEN, individual components may be active but the circuit as a whole is not operating.
• When a circuit is CLOSED, both the individual components and the circuit as a whole should be operating.

It May Surprise You To Know… that computers recognise only two numbers, zero and one. In computers the numbers are represented by electronic switches. An OPEN switch represents a zero and a CLOSED switch represents a one. With enough switches, almost anything can be stored and represented as numbers. Another name for these computer switches is “bits”. The 'bits' are stored in computers' memories and recalled using the keyboard and an application.

It may not be obvious, but it is true to say that almost all of shared human knowledge is now stored in switches. That is one reason why it is so important to understand how switches work!

Circuits without switches are not very useful because, without a switch, you would have to actually remove or add a component to the circuit to turn the device on/off.

Turning devices on/off without using a switch is also often unsafe.

Adding or removing a wire may have the same effect as CLOSING or OPENING a circuit.

You can think of a switch as being a way to MAKE or BREAK a circuit (in the same way that adding or removing a wire can make or break a circuit).

Opening/closing a switch or adding/removing a wire, may have the same effect, but using a switch is usually easier, more efficient and safer.

To make a circuit, use one or two Alligator Clips to connect objects to the circuit. To make a simple switch, almost any metal object will work. Simply connect the object to the circuit using alligator clips. You may also create a switch using a MaKey MaKey board and some other object - for example, using an apple. If the apple is conductive, connecting alligator clips to the apple will CLOSE the circuit and the computer thinks that someone has pressed a key on the keyboard. Because a computer key is only a switch, it is true to say that you are using an apple and a Makey Makey to create a switch.

Try connecting a reed switch using your test lead alligator clips.

Use the magnet to CLOSE the circuit and turn the torch OFF and ON.

Record your results in the results table.

Try creating a simple switch using some conductive materiala and your test lead alligator clips.

Connect the material into the circuit and try to turn the torch OFF and ON.

Record your results in the results table.

You can use the Makey Makey as an electronic switch. Find four items to connect to your test leads.

Try connecting each item to CLOSE the circuit and use the Makey Makey to play a sound or enter a key on a computer.

Record your results in the results table.

Collect four items to connect to your test leads. Try connecting each item to CLOSE the circuit and turn the torch OFF and ON.

Record your results in the results table.

Most bulbs and globes are being replaced by devices called Light Emitting Diodes (LEDs). Unlike bulbs/globes, LED's have a positive and negative lead and must be connected the right way round in a circuit (bulbs and globes don't care which way round they are connected in relation to positive and negative. LEDs also require an additional component called a resistor to limit the amount of electrical energy flowing through them. Here are some examples of what LED's look like:

Tired of boring old wires and buzzers….

• Squishy Circuits - build circuits using Play-Doh
• Make your own conductive paint from Vitamin C & Copper Sulphate
• Make conductive, coloured inks
• Bare paint & some innovative ways of connecting circuits