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ELECTRICITY SAFETYMiss. Gm GeddesSeptember 2015Victory housebit.ly/1cO4vmZ

RECAPIs a house connected in parallel or series. WHY??

The disadvantage to having a house connected in parallel is that it can become OVERLOADED, this can cause a FIRE , which can BURN DOWN YOUR HOUSE

ELECTRICITY SAFETY TIPS

OUTCOMES FOR THIS LESSON

Draw a circuit in parallel or series containing a fuseExplain why certain household appliances need to be earthedDiscuss how a house is wiredDistinguish between the different connections found in a plugRelate the use of electricity to a South African contextName the negative effects of illegal connectionsDifferentiate between a fuse and a circuit breaker

EARTHING The only time it is used is when something goes wrong inside the machine.

If the live wire is exposed and touches the metal casing of the washing machine, you could get an electric shock if you then touch the metal casing.

However, the earth wire is connected to the metal casing so that the current goes through the earth wire and into the ground instead of shocking you.

The earth wire has a very low resistance and so a strong current will easily go through it.

EXAMPLE OF EARTHINGTAKE NOTEThe earth wire issometime just green orjust yellow instead ofstriped.

What does an earth wire do?The earth wire completes the circuit and connects the live wire to the ground.

This is a short circuit. The washing machine will stop working because none of

the electricity will flow through the motor.

What would happen if there was earth cable?If there was no earth wire then the metal casing of the washing machine would become part of the electrical circuit and anyone who touched it would get an electrical shock.

That is why an earth wire is an important safety feature on any electrical appliance.

This is how it looksinside a washing machine:

SHORT CIRCUIT An extra electrical pathway is made.

The extra electrical pathway has very low resistance and so the current increases.

This increased current can damage appliances and cause overheating.

WHAT IS A FUSE A fuse is a wire which will melt if the current travelling through becomes toolarge due to a fault, GIVE AN EXAMPLE: SHORT CIRCUIT, OVERLOAD

Thus the circuit is broken and no current can flow, The photo is of a 5 ampere fuse. It will if a current of more than 5 amperes passes through it.Circuit breakers are more commonly used in households.

Circuit breakerA circuit breaker is similar to a fuse except that it can be reset.Basically a switch that trips

How does a circuit breaker work?1. When the switch is on, the current flows through the device, from the leftthrough the moving contact and across to the stationary contact.

2. It then goesaround the electromagnet and out the other side.

3.The iron catch is holding themoving contact in place so that the circuit is complete.

4.If the current passingthrough the circuit breaker increases, the electromagnet becomes stronger.

5.If the current gets to unsafe levels, the electromagnet becomes strong enough topull the iron catch lever.

6.This releases the moving contact so that the circuitbreaks and the electricity is shut off, as shown in the following diagram.

DISADVANTAGEADVANTAGEFUSEHas to be replacedCheap, easily availableCIRCUIT BREAKERSExpensiveCan just be turned on again

REMEMBER An electric charge will move from where there is a lot of potential energy to where this is less potential energyDO YOU REMEMBER LEARNING ABOUT LIGHTNING?

The excess electrons from the clouds move to the ground and transfer a large amount of energy in the process.

EARTH LEAKAGE -type of circuit breakerUsed in households and businessesIt works for different areas in the house / businessThe breakers are found on the distribution board

What does an earth breaker do?The earth leakage circuit breaker is a safety device which can switch off the electricity supply to the house. The earth leakage is able to detect if any current is moving through the earth wire. If current is moving through the earth wire then there is a short circuit somewhere, for example as explained with the washing machine. The earth leakage circuit breaker then shuts down all the current as a safety measure.

LIGHTNING Can be a danger to an electric circuitLightning spikes or conductors are used often

When lightning strikesThe surge of current will flow through the rod and safely into the ground. This will help prevent fires in households

HOW TO SURVIVE LIGHTNING

Wiring a 3- pin plug a brown live wire a blue neutral wire a green and yellow striped earth wire

The wire which enters ourhomes is the live wire. The neutral wireleaves our homes and is earthed as itleaves the house. The earth wire has avery low resistance and is connectedthrough the plug socket to the earthcable of the house. The earth cableleads into the ground.

BRUIN REGS (power into house) LiveBLOU LINKS (power out of house) NeutralGROEN EN GEEL BO (earth the house)The electrical plug has three metal pins. Each pin has a hole in it with a smallmetal screw. Loosening the screw opens the hole, tightening the screw closesthe hole. Let's take a look inside a plug to see how to wire it.

ILLEGAL CONNECTIONSAn illegal electricity connection is made when a person attaches their home'selectrical circuit to the national grid without a meter. This is done without theconsent or knowledge of Eskom. Eskom cannot monitor the electricityconsumption and so the electricity is being stolen as these consumers do not pay for the electricity.

ILLEGAL CONNECTIONSSome people make money bysupplying illegal connections and others have no legal way to accesselectricity and so they resort to illegal connections. Others have access to legal electricity, but prefer not to haveto pay for it. Not only are these types of electrical connections illegal andconsidered energy theft, they are also very dangerous,

EFFECTS OF ELECTRICITY THEFT Stability and quality is influencedCan lead to power interruptionsEskom cannot keep up with the increasing demand to provide electricityBig financial lossesPeople and animals can be shocked to death or get seriously hurt.

SUMMARY Electricity can be dangerous and so we need safety devices such as fuses, circuit breakers and earth leakages to reduce risk.

A fuse is a safety device with a very low resistance wire, designed to melt if it experiences a large enough current. This breaks the circuit and protects the appliance, as well as preventing a possible fire hazard.

A circuit breaker is like a fuse, but acts as a switch which breaks the circuit in response to an electrical fault or overload. It can be reset.

Many electrical appliances with a metal casing have an earth wire attached to prevent electric shocks if there is a short circuit.

SUMMARY A three-pin plug has three wires: a brown live wire, a blue neutral wire and a green and yellow striped earth wire.

The earth wire has a very low resistance and is connected through the plug socket to the earth leakage system of the house, and into the ground.

A plug must be connected properly in order to make sure that it is safe to use.

Illegal electricity connections are both dangerous and illegal. It is a crime to steal electricity.

THE ELECTRICITY SONG