Switches
This Topic is About...
- I will describe how a simple switch is used to open and close a circuit.
- I will make a prediction and test it to see if it is correct.
- I will see that an electrical device will not work if there is a break in the circuit.
- I will choose equipment to carry out an investigation and use it appropriately.
- I will identify risks and carry out practical work safely.
You’re going to be a science explorer!
Key Words
- switch
Tap to Learn the Meaning!
- switch: A device that turns electricity on or off in a circuit.
Well done! You’ve learned a key word about electrical circuits.
Putting a switch in a circuit
Aswitch is another component in an electrical circuit. The switch turns the electric current on or off. It is the same idea as turning a tap on or off.
So far you have made circuits with no switch. To break the circuit you broke the wire. A switch lets you turn a lamp on and off when you like, without having to break wires.
Let’s Investigate!
Question: How can you make a simple electrical switch?
Equipment: A small block of wood, two drawing pins, a wire, a sharp knife or wire trimming tools, a metal paper clip (not plastic-coated), a plastic or wooden chopstick
Method:
- Strip the plastic off the ends of two pieces of wire.
- Be careful! If using a knife to strip the plastic, ask your teacher for help or use wire trimming tools instead.
- Wind one end of each wire around a drawing pin and fix the pins onto the block of wood.
- Place the metal paper clip under one pin and let the other end rest near the second pin.
- Move the paper clip until it touches the other drawing pin to complete the circuit. Use a wooden or plastic stick (like a chopstick) to do this safely.
- To switch off, lift the paper clip off the second pin. This breaks the circuit.
Questions:
- Why do you use a metal paper clip to make the switch?
- Why do you use metal drawing pins to make the switch?
- Why is the base of the switch made of wood?
- Suggest other suitable materials for making a switch.
Tap to See Answers
- 1: The metal paper clip conducts electricity, allowing current to flow when it touches both drawing pins.
- 2: Metal drawing pins are conductors, so they help complete the circuit by connecting the wires to the switch.
- 3: The wooden base is an insulator; it prevents electricity from flowing through and protects against shocks.
- 4: Other materials like brass strips, aluminium foil, or steel clips could also be used to make a switch.
Excellent work! You’ve built a simple and safe electrical switch to control a circuit.
Let’s Investigate!
Question: How can you make a complete circuit with a switch?
Equipment: A switch, a cell in a cell holder, a lamp in a lamp holder, 30 cm wire, a sharp knife or wire trimming tools, scissors
Method:
- Make a circuit like the one shown in the diagram.
- Remember to follow safety rules. Wait for your teacher’s help if you need to use a knife to strip the plastic from the ends of the wire.
- Predict what will happen when you close the switch.
- Close the switch and observe the lamp. What happens?
- If the lamp does not light up, check all your connections in the circuit and try again.
Questions:
- Why does the lamp light up when you close the switch?
- What must you do with the switch to break the circuit?
- Draw the circuit you made. Label the cell, the wire, the switch, and the lamp.
- Why did you need to check your connections if the lamp did not light up?
- Which safety rules did you follow during this investigation?
How am I doing?
- How well did your partner do in the investigation?
- Did your partner connect the components of the circuit confidently on their own, or did they need some help or a lot of help?
- Did your partner use the switch to open or break the circuit confidently on their own, or did they need some help or a lot of help?
Tap to See Answers
- 1: The lamp lights up when the switch is closed because the circuit is complete and electricity can flow through it.
- 2: To break the circuit, open the switch. This stops the flow of electricity.
- 3: The circuit should show a complete loop: cell → wire → switch → lamp → back to the cell.
- 4: Checking connections ensures that all wires and components are properly attached, allowing electricity to flow without gaps.
- 5: Safety rules include cutting away from you, holding insulated parts of the wire, and asking for help when using sharp tools.
Fantastic job! You’ve learned how a switch controls the flow of electricity in a simple circuit.