Electrical Safety Matters SP0009

Transcription

1 Electrical Safety Matters Resource Description Understanding fuses and their ratings helps pupils to appreciate their role as safety devices and subsequently how to use electricity safely in the home. The Fire Service all too often sees the consequences of electrical accidents and so are well placed to teach this element. National Curriculum Key Stage 2/Citizenship Key Stage 2/PSHE Key Stage 2/Science Key Stage 3/PSHE Key Stage 3/Science QCA Key Stage 2/Science/Unit 4F Circuits and conductors Key Stage 2/Science/Unit 6G Changing circuits Key Stage 3/Science/Unit 7J Electrical circuits Resources Electrical Gloves Worksheet - Electrical Safety Matters Common sense guidelines - Electrical Safety Matters Electrical dangers in the home Possibly examples of fuses, plugs

2 Lesson Plan Introduction Introduce yourselves i.e. FFs.. from.. fire station. Explain that you are on duty and may be called away (if applicable). Establish the classroom ground rules i.e. hands up, no calling out. 2 mins Aims and Objectives To educate pupils about electrical circuits, fuses and electrical safety To ensure pupils will understand how fuses work as safety devices and understand how to use electricity safely in the home 2 mins Starter Activity 6 mins Which appliances in your home are powered by a) batteries? and b) mains electricity? Why is this? This is because some appliances require a lot more electricity to operate and batteries cannot easily provide this. Mention that mains electricity is very dangerous and can be fatal so we must be very careful when using it. Recap / Introduce some basic electrical safety. Never touch electrical sockets/switches (lights) with wet hands Never use electrical equipment in the bathroom Never stick anything into an electrical socket Any of the above could result in electrocution Main Activity 30 mins It is possible for faults to develop in electrical circuits which may lead to the circuit conducting more electricity than it is designed to do; this can cause overheating of the circuit or components which could lead to fire. In order to prevent this from happening appliances and circuits are fitted with fuses (usually located in the plug). Explain how fuses work. A fuse is a simple component in series that breaks the circuit if there is too much electricity flowing through the circuit. A fuse is essentially a piece of wire that conducts electricity. If the electricity in the circuit increases then more electricity is forced through the same wire, this causes the wire to heat up. If this continues then the fuse wire will get to a point where it gets too hot, melts and breaks. With the fuse wire broken no current can flow through the circuit. This will prevent any other parts of the circuit overheating and possibly causing a fire. The circuit will not be able to operate again until the fuse is replaced. Fuses come in different sizes depending on what circuit they are in. Table 1 shows what fuse ratings should be used with various appliances. Explain what would happen if the wrong size fuse is put into the circuit. Fuse too small = Fuse will break before enough current can be generated to operate parts in the circuit. Fuse too large = Fuse will not break at a low enough current and other parts of the circuit may overheat first and catch fire Which one is more dangerous? Fuse too large

3 Fuses can come in all shapes and sizes. Mini Circuit Breakers (MCBs) and Residual Current Devices (RCDs) perform the same function but have the advantage of being able to be reset using a switch and are more sensitive. Explain that a common accident when using electricity occurs when electric lawnmowers run over the power lead. Ask the pupils if they know what happens in this case? Ensure that they understand if the power lead is cut it could cause a short circuit and because electricity will always find the easiest route it can travel up the mower and through the operator, resulting in electrocution. In order to stop this from happening an RCD can be put in the circuit (usually between the plug and the socket), this will break the circuit if a short circuit occurs. Show Electrical gloves and explain situations when we may need to use them. Ask why the pupils think that we are safe to touch some things safely with these on. They should recognise it is safer for us because of the material of which the gloves are made (insulator) and that they are regularly tested. Explain however they are only safe to use up to a certain level and that it is still dangerous. Apart from using the correct fuses we should be able to spot other electrical hazards in the home. Danger signs include: Hot plugs and sockets Fuses blowing for no obvious reason Flickering lights Scorch marks on sockets or plugs Keep liquids away from electrical appliances, plugs and sockets. Keep the toaster clean and away from overhanging obstructions i.e. curtains Do not overload sockets as this could lead to overheating Do not use plugs with coloured wires sticking out of the bottom or power leads that have been taped together Closing Activity Complete the Electrical Safety Matters worksheet. or log on to and play the Dangers in the Kitchen game. 10 mins

4 Electrical Safety Matters All appliances should come with a handbook containing details of the power rating in Watts. This table shows the correct fuse size for various power ratings. Table 1 This table could be drawn on the board getting the pupils to help fill it out. See if pupils know how much power each appliance uses; see if they recognise that a larger fuse is needed for more powerful appliances. Power Rating Up to 720 Watts (Television, Radio) From Watts (Vacuum cleaner) From Watts (Kettle) Fuse Rating 3 Amps 5 Amps 13 Amps 1) Imagine a simple circuit with a vacuum cleaner that has a power rating of 1000 Watts, (the correct fuse rating is 5 Amps) but some one has used a 3 Amp fuse in the plug. What will happen if someone uses the vacuum cleaner? 3 Amp 1000 Watts The vacuum cleaner is designed to work at a higher power rating than the fuse will allow so the fuse will blow and break the circuit. This will continue to happen if a fuse with too low a rating is put in. 2) What about a simple circuit with a computer that has a power rating of 400Watts, (the correct fuse rating is 3 Amps) some one has put a 5 Amp fuse in the plug. What will happen if someone uses the computer? 5 Amp 400 Watts The computer has a power rating of 400 Watts and so a 3 Amp fuse would prevent too much power passing through the circuit and possibly overheating the computer. As the wrong fuse has been put in it will allow too much power through the circuit without blowing the fuse and so could overheat the computer and cause a fire.

5 Pupil Sheet Electrical Safety Matters Common sense guidelines when using Electricity Never electrical sockets or light switches with. Never use electrical equipment in the. Never stick into an. Do not touch bare or freyed wires because you could receive an electric. If too many appliances are plugged into a single socket it may and cause a. As a safety measure most appliances are fitted with a plug which contains a. In your own words describe what these devices are and how they protect a circuit if a fault or short circuit occurrs. What advice could you give to someone who finds a person who might have had an electric shock?

6 Answer Sheet Electrical Safety Matters Common sense guidelines when using Electricity Never touch electrical sockets or light switches with wet hands. Never use electrical equipment in the bathroom. Never stick a knife into an electric toaster. Do not touch bare or freyed wires because you could receive an electric shock. If too many appliances are plugged into a single socket it may overheat and cause a fire. As a safety measure most appliances are fitted with a plug which contains a fuse. In your own words describe what these devices are and how they protect a circuit if a fault or short circuit occurrs. A fuse is a piece of wire which conducts electricity. As electricity in the circuit increases and flows through the wire, the wire heats up. If this continues the fuse wire will get too hot, melt and break the circuit, preventing overheating of any other part of the circuit and stopping any fire. What advice could you give to someone who finds a person who might have had an electric shock? Firstly switch off the current. If not possible take a non-conductive item e.g. broom handle and push away the source of the current. Then check to establish if the patient is breathing. If not use Resuscitation techniques and call for emergency aid. Always advise a medical checkup as there may be internal injuries even if external burns appear minor.

7 Pupil Sheet Electrical Safety Matters Electrical dangers in the home In the picture you should find at least 10 dangers. Circle them and say why you think they are dangerous.

8 Answer Sheet Electrical Safety Matters Electrical dangers in the home Pupil Question: In the picture you should find at least 10 dangers. Circle them and say why you think they are dangerous. SP00009