This practical requires some preparation to ensure the safety of both pupils and staff. The safety precautions should not be compromised.
Equipment required (per set):
The lesson essentially involves pupils correctly wiring a three pin mains plug to a length of cable.
The plugs used are typical mains three pin plugs. All modern plugs have black 'sleeves' on the live and neutral pins to protect fingers when plugging and unplugging and also to prevent accidental contact between metal objects and the pins. All plugs used in your school and home should now look like this. If they do not have this sleeving, change them.
- Mains three pin plug (complete with fuses etc-new if possible)
- 50CM length of three core mains cable
- Wire cutter
The main possible danger in this practical is that a pupil will wire a plug using a length of cable and then plug it in to a live socket, risking electrocution. The following precautions are included for guidance only, further clarification can be sought from CLEAPSS and ASE.
The plugs should be 'doctored' to ensure they cannot be plugged in. Either bend the earth pin slightly, drill a hole in the earth pin and put a nut and bolt through it or as in these photos, attach a band of shrink sleeving to the earth pin.
Shrink sleeving can be purchased in lengths from electrical retailers such as Maplin and Rapid. Cut small bands and place over the pin. Use a heat gun to directly heat the band where it will shrink around the pin. Several layers should ensure a tight fit and make sure the pin will not fit into the socket.
To increase safety, where possible isolate the mains sockets in the classroom being used by turning off the power at the master switch.
The cables used can be any type of mains three strand cable, available from many suppliers and high-street outlets. These should also have shrink sleeving or insulation tape applied to the free end so that uninsulated wires are not exposed in case all other safety precautions should fail.
You may need to check the equipment before each use to ensure all fuses and cable grips and screws are intact and all cables are long enough to be used properly.
Some teachers may also require a 'cut-out' plug worksheet to either accompany or be used instead of this practical lesson. This sheet includes a simple drawing of a plug and all of its components which can be cut out and arranged correctly into pupil books. We have provided a copy of this sheet (see above in downloads section). It can be freely copied and distributed within your school.