Fuse or mcb L Live
FuseN Neutra or lmcb L Live
N Neutral
Fuse or mcb L Live
FuseN Neutra or lmcb L Live
N Neutral
Fuse or mcb LLive Two-way switch
NNeutral
Fuse or mcb LLive Two-way switch
NNeutral
Socket 1 Socket 2
Socket 1 Socket 2 Fuse or mcb L Live N Neutral E Earth Fuse or mcb L Live Fuse or mcb LLive Two-way switch N Neutral Fuse EorEarth mcb LLive Two-way switch NNeutral NNeutral
Socket 1 Socket 2 Socket 3 Socket 4 Socket 1 Socket 2 Socket 3 Socket 4
Fuse or mcb LLive Fuse or mcb LLive
E Earth N Neutral
E Earth N Neutral
Socket 1 Socket 2
Socket 1 Socket 2 Fuse or mcb L Live Fuse or mcb L Live N Neutral E Earth Fuse or mcb L Live N Neutra l ElectricityFuse or mcb L Live in Home N Neutral the E Earth N Neutra l Electricity in Home the
The second circuit is used where there are two switches, for example at How is electricity supply delivered to each of two doors to a room. The type of switch used is called a two-way a house? switch and, if the light is off, as drawn, either switch will switch it on. If the Socket 1 Socket 2 Socket 3 Socket 4 light is on, either switch can switch it off. Examine the circuit and see why The ESB maintains a national network of high tension power this is so. Fuse or mcb LLive lines. The voltages on these lines are as high as 400 kV. Such The second circuit is used where there are two switches, for example at voltages are not delivered to domestic premises. Instead the Two-way switch How is electricity supply delivered to F use or mcb LeachLive of two doors to a room. The type of switch used is called a two-way voltage is stepped down at transformers to a more suitable Socket 1 Socket 2 Socket 3 Socket 4 switch and, if the light is off, as drawn, either switch will switchE Earth it on.N NeutraIf thel lowera house? value. A two-wire cable is used to bring electricity to NNeutral light is on, either switch can switch it off. Examine the circuit and see why the home. The neutral is connected to a metal plate in the Fig.5 A ring circut with four sockets What is ESB Customer Supply? The ESB maintains a national network of high tension power this is so. Fuse or mcb LLive ground, and so is at 0V. Therefore, the neutral is said to be Fig.3 Lighting circut, two two-way switches ESB Customer Supply supplies electricity to 1.8 million earthed.lines. The voltage voltages on the on live these wire alternateslines are to as 311V high above as 400 kV. Such Other circuits customers (on the basis of published tariffs). It provides andvoltages below this are 50 not times delivered a second to giving domestic an effective premises. 220V. Instead the Fuse or mcb LLive OtherT wo-way types of switch domestic load use large currents and are supplied by Lighting circuits do not require large currents. Typically, a circuit breaker customers with services which meet their needs (for Atvoltage the house, is a stepped main fuse anddown meter at aretransformers installed. to a more suitableor fuse of 6 amps is used. The conductors in lighting cables therefore independent radial circuits which are not connected to any other appliance. need not be very thick. One 100 Watt bulb uses less than half an amp as The most common are immersion (water) heaters, cookersE andEarth electricN Neutral example, budget accounts, direct debit and other payment NNeutral lower value. A two-wire cable is used to bring electricityshown below. to showers. Cookers and showers require very thick conductors. options) and with appropriate advice to help them use How is electricity distributed in the house? Fig.5 A ring circut with four sockets the home. The neutral is connected to a metal plate in the Fuse or mcb L Live electricity more efficiently while saving money at What the is ESB Customer Supply? IV = Power 0.45 A x 220V = 100 W The cable is then terminated on a consumer unit. From the consumer unit Why use fuses and mcbs? same time. ground, and so is at 0V. Therefore, the neutral is said to be Socket 1 Socket 2 different circuits are run to the various points where electricity is needed Fig.3 Lighting circut, two two-way switches A fuse is a wire that will get hot and melt (“blow”) if the circuit is above its ESB Customer Supply supplies electricity to 1.8 million - lights,earthed. sockets, The cookers voltage etc. These on circuits the liveare all wire fed with alternates the 220V from to 311VTherefore, above a 6 amp mcb couldN safelyNeutra lprotect a circuit feeding more than Other circuits ESB Customer Supply employs approximately 650 people ten 100 W bulbs. In practice, the lighting circuits for a number of rooms are rated current. By melting, the fuse disconnects the live wire from the load, customers (on the basis of published tariffs). It provides the consumer unit, so all domestic circuits are in parallel. 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This E Earth lighting circuits in a house. current is too large. It is a switch with contacts that open very quickly. example, budget accounts, direct debit and other payment can be a fuse or a miniature circuit breaker (mcb). need not be very thick. One 100 Watt bulb uses less than half an amp as The most common are immersionAs (water) a business heaters, unit withincookers ESB, and Customer electric Supply has over shown below. Circuit breakers are faster and more preciseshowers. than fuses Cookers and they and can beshowers require75 years very experience thick conductors. in providing electricity servicesoptions) to and with appropriate advice to help them use reset. The circuit breakers on a distribution board are very compact and How is electricity distributed in the house?Power circuits for appliances (sockets) customers throughout Ireland. Fuse or mcb L Live are called miniature circuit breakers. electricity more efficiently while saving money at the IV = Power 0.45 A x 220V = 100 W The cable is then terminated on a consumer unit. From the consumerThe term unit appliance is a general term for any thing powered through a Why use fuses and mcbs?Ireland has one of the fastest-growing electricity marketssame in time. plug and a flexible cable. The standard plug is designed to carry up to Socket13 1 Socket 2 different circuits are run to the various points where electricity isamps, needed though most appliances need considerably less. Inside the plug What is a residual current device (RCD)? the developed world. It grew over 40 per cent over the last N Neutral A fuse is a wire that will get hot and melt (“blow”) if the circuit is above its - lights, sockets, cookers etc. These circuits are all fed with the 220Vthere isfrom a fuse. The fuseTherefore, is usually either a 6 ampa 3-amp mcb fuse could (for appliances safely protect up a circuit feeding more than 10 years, far ahead of average growth in the rest of Europe.ESB Customer Supply employs approximately 650 people One device that reduces the likelihood of harmrated from electriccurrent. shock By is melting, the RCD. the fuse disconnects the live wire from the load, the consumer unit, so all domestic circuits are in parallel. to 660 Watts) or a 13-ampten 100fuse W(for bulbs. appliances In practice, up to almost the 3 lighting kilowatts). circuits forElectricity a number enters of and rooms leaves are a house through the live and neutral wires. The market has been fully opened to competition since Fuse or mcb L Live reducing the risk of overheating and fire. and in any one year issues 11 million bills and handles over Where a 3-amp fuse isconnected sufficient it shouldin parallel be used. and A suppliedfault then is through more oneNormally, mcb. It theis not amount convenient of electricity entering is matched by exactly the February 2005. The live wire connection to every circuit is fed through a safetylikely device to blow this fuse only, rather than both blow it and also trip the mcb 3 million telephone calls from customers. toN haveNeutra alll lights fail at the sameTwo-way time switch so it is commonsame amount to have leaving. two or If morethere is a fault however, it often involves some on the consumerFuse unit. orSocket mcb L1LiveSocket 2 Socket 3 Socket 4 Like a fuse, a miniature circuit breaker disconnects the live wire if the which cuts off the circuit if the current demanded becomes excessive. This lighting circuits in a house.E Earth electricity from a live wire going to earth, possibly through a person. This is called a residual current or an earth-leakagecurrent current. is too large. It is a switchYou with can contactsfind out more that about open ESB very Customer quickly. Supply by loggingAs a business unit within ESB, Customer Supply has over can be a fuse or a miniature circuit breaker (mcb). In general, almost all the powerNNeutra consumedl in a house is converted into onto www.esb.ie and www.sciencetechnologyaction.com Fuse or mcb LLive Circuit breakers are faster and more precise than fuses and they can be heat. Appliances that generate a lot of heat, like electric fires or kettles, A fault current to earth has implications. Even 100 mA can cause a fire. An 75 years experience in providing electricity services to Fig.1 Image of consumer unit and meter use large currents andPower consume a lotcircuits of power. At 220V, for the appliances current per even (sockets) smaller current, 30 mA, can kill a person.reset. The circuit breakers on a distribution board are very compact and kilowatt is about 4.5 amps. Many other appliances such as radios or are called miniature circuit breakers. customers throughout Ireland. The RCD consists of a circuit breaker which is tripped if the currents The conductors in the circuit are copper and are insulated. The resistance mobile phone chargersThe need term little power. appliance is a general term for any thing powered through a must be low enough that, E Earth N Neutral entering and leaving on the live and neutral wires differ by more than 30 Be careful with electricity Ireland has one of the fastest-growing electricity markets in When sockets are fittedplug as shown and below,a flexible the circuit cable. is called The astandard radial circuit. plug is designedmA. Domestic to carryRCDs willup usuallyto 13 also trip if a certain current, for example • at the rated current, the drop in voltage between the consumer unit (It radiates out from the consumer unit.) Because each socket can supply amps, though most appliances need considerably63 A, isless. exceeded. Inside the plug What is a residual current‘Electricity isdevice so much a part(RCD)? of modern living that we can oftenthe developed world. It grew over 40 per cent over the last and the load is low 13 amps there is a limit to the number of sockets that can be supplied by take it for granted. It is a powerful and versatile energy but can be one cable. there is a fuse. The fuse is usually either a 3-ampThe fuse current (for for appliances most or all of up the circuits inOne modern device houses that isreduces fed via an the likelihood of harm from electric shock is the RCD. 10 years, far ahead of average growth in the rest of Europe. • the copper does not get too hot. dangerous if not used properly.’ to 660 Watts) or a 13-amp fuse (for appliances RCDup to which almost is between 3 kilowatts). the main fuse and their mcbs or fuses. Cables with large diameters have less resistance than those with smaller Electricity enters and leaves a house through the live and neutral wires. The market has been fully opened to competition since Fig.4 A radial circut with two sockets diameters. In general, domestic circuits are classified as lighting circuits Where a 3-amp fuse is sufficient it should be used. A fault then is more Normally, the amount of electricitySerious entering accidents is with matched electricity by in exactlythe home theare rare but each year Socket 1 Socket 2 February 2005. or power circuits. likely to blow this fuse only, rather than both blowWhat it and is also the trip earth the mcb rod? same amount leaving. If there is athere fault is ahowever, small number it often of fatalities involves and some serious injuries. Most of Fuse or mcb LLive Two-way switch on the consumer unit.Socket 1 Socket 2 Socket 3 Socket 4 electricity from a live wire going tothe earth, accidents possibly that occur through are due a eitherperson. to carelessness This or to a lack The earth wire in a domestic circuit is connected to an earth electrode in of awareness of some basic rules that should always be observed How lighting circuits are connected Fuse or mcb L Live You can find out more about ESB Customer Supply by logging In general, almost all the power consumed in athe house ground is which converted provides into a low-resistance is calledpath via a the residual ground itselfcurrent to or an earth-leakagewhen using electricity.’ current. N Neutral NNeutral onto www.esb.ie and www.sciencetechnologyaction.com Two simple lighting circuits are shown below. The first circuit is used where Fuse or mcb the transformer. At the transformer, the neutral is connected to a plate in heat. AppliancesE Earth LLive that generate a lot of heat, like electric fires or kettles, there is a single switch, usually at the door of a room. the ground. This is why electricity will flow Afrom fault live current to earth. to earth has implications.The above Even is an 100 extract mA fromcan thecause booklet a fire. The SafeAn Use of Electricity Fig.1 Image of consumer unit and meter use large currents and consume a lot of power. At 220V, the current per even smaller current, 30 mA, can killin the a person.Home which is produced by the ESB in cooperation with the Fuse or mcb L Live kilowatt is about 4.5 amps. Many other appliances such as radios or Electro Technical Council of Ireland. The booklet contains essential An alternative approach is the ring circuit. Here the circuit takes the form The RCD consists of a circuit breakerinformation which on electrical is tripped safety if in thegeneral currents and also hints and rules The conductors in the circuit are copper and are insulated. The resistanceof a ring with both endsmobile of the ringphone connected chargers to the need consumer little unit. power. Both which you should always follow. must be low enoughN Neutrathat,l “live” wires are connected to one Emcb,Earth both neutralsN Neutra tol the neutral, both entering and leaving on the live and neutral wires differ by more than 30 Be careful with electricity When sockets are fitted as shown below, the circuit is called a radial circuit. earths to earth. This has the advantage that the current demanded can mA. Domestic RCDs will usually also trip if a certain current, for example • at the rated current, the drop in voltage between the consumer unit (It radiates out from the consumer unit.) Because each socket can supply The booklet is available on www.esb.ie. flow two ways and is spread over two conductors. A ring circuit can 63 A, is exceeded. ‘Electricity is so much a part of modern living that we can often Fig.2 and Lighting the circut,load oneis low switch contain more sockets 13than amps two radial there circuits. is a limit to the number of sockets that can be supplied by take it for granted. It is a powerful and versatile energy but can be one cable. The current for most or all of the circuits in modern houses is fed via an • the copper does not get too hot. dangerous if not used properly.’ RCD which is between the main fuse and their mcbs or fuses. Cables with large diameters have less resistance than those with smaller Fig.Socket4 A 1 radialSocket circut 2 Socket with 3 Stwoocket sockets4 diameters. In general, domestic circuits are classified as lighting circuits Serious accidents with electricity in the home are rare but each year Socket 1 Socket 2 or power circuits. Fuse or mcb LLive What is the earth rod? there is a small number of fatalities and serious injuries. Most of the accidents that occur are due either to carelessness or to a lack The earth wire in a domestic circuit is connected to an earth electrode in of awareness of some basic rules that should always be observed How lighting circuits are connected Fuse or mcb L Live the ground which provides a low-resistance path via the ground itself to when using electricity.’ Two simple lighting circuits are shown below. The first circuit is used where E Earth N NeutraNl Neutral the transformer. At the transformer, the neutral is connected to a plate in E Earth the ground. This is why electricity will flow from live to earth. there isFuse a singleor mcb switch,LLive usually at the doorTwo-way of a switchroom. The above is an extract from the booklet The Safe Use of Electricity in the Home which is produced by the ESB in cooperation with the FuseN orNeutra mcbl L Live Electro Technical Council of Ireland. The booklet contains essential An alternative approach is the ring circuit. Here the circuit takes the form information on electrical safety in general and also hints and rules of a ring with both ends of the ring connected to the consumer unit. Both which you should always follow. N Neutral “live” wires are connected to one mcb, both neutrals to the neutral, both earths to earth. This has the advantage that the current demanded can The booklet is available on www.esb.ie. flow two ways and is spread over two conductors. A ring circuit can Fig.2 Lighting circut, one switch contain more sockets than two radial circuits.
Socket 1 Socket 2 Socket 1 Socket 2 Socket 3 Socket 4
Fuse or mcb L Live Fuse or mcb LLive N Neutral E Earth
E Earth N Neutral
Fuse or mcb LLive Two-way switch
NNeutral
Socket 1 Socket 2 Socket 3 Socket 4
Fuse or mcb LLive
E Earth N Neutral
Socket 1 Socket 2
Fuse or mcb L Live N Neutral E Earth
Socket 1 Socket 2 Socket 3 Socket 4
Fuse or mcb LLive
E Earth N Neutral Fuse or mcb L Live
FuseN Neutra or lmcb L Live
N Neutral
Fuse or mcb L Live
FuseN Neutra or lmcb L Live
N Neutral
Fuse or mcb LLive Two-way switch
NNeutral
Fuse or mcb LLive Two-way switch
NNeutral
Socket 1 Socket 2
Fuse or mcb L Live Socket 1 Socket 2 N Neutral E Earth Fuse or mcb LLive Two-way switch Fuse or mcb L Live N Neutral Fuse EorEarth mcb LLive Two-way switch NNeutral NNeutral
Socket 1 Socket 2 Socket 3 Socket 4 Socket 1 Socket 2 Socket 3 Socket 4
Fuse or mcb LLive Fuse or mcb LLive
E Earth N Neutral
E Earth N Neutral
Socket 1 Socket 2
Socket 1 Socket 2 Fuse or mcb L Live Fuse or mcb L Live N Neutral E Earth Fuse or mcb L Live Fuse or mcb L Live N Neutra l Electricity in Home N Neutral the E Earth N Neutra l Electricity in Home the
The second circuit is used where there are two switches, for example at How is electricity supply delivered to each of two doors to a room. The type of switch used is called a two-way a house? switch and, if the light is off, as drawn, either switch will switch it on. If the Socket 1 Socket 2 Socket 3 Socket 4 light is on, either switch can switch it off. Examine the circuit and see why The ESB maintains a national network of high tension power this is so. Fuse or mcb LLive lines. The voltages on these lines are as high as 400 kV. Such The second circuit is used where there are two switches, for example at voltages are not delivered to domestic premises. Instead the Two-way switch How is electricity supply delivered to each of two doors to a room. The type of switch used is called a two-way Fuse or mcb LLive voltage is stepped down Socketat transformers 1 Socket to2 a S ocketmore 3 suitable Socket 4 switch and, if the light is off, as drawn, either switch will switch it on. If the E Earth N Neutral a house? lower value. A two-wire cable is used to bring electricity to NNeutral light is on, either switch can switch it off. Examine the circuit and see why the home. The neutral is connected to a metal plate in the Fig.5 A ring circut with four sockets What is ESB Customer Supply? The ESB maintains a national network of high tension power this is so. Fuse or mcb LLive ground, and so is at 0V. Therefore, the neutral is said to be Fig.3 Lighting circut, two two-way switches ESB Customer Supply supplies electricity to 1.8 million lines. The voltages on these lines are as high as 400 kV. Such earthed. The voltage on the live wire alternates to 311V above Other circuits customers (on the basis of published tariffs). It provides voltages are not delivered to domestic premises. Instead the Fuse or mcb LLive Two-way switch and below this 50 times a second giving an effective 220V. Other types of domestic load use large currents and are supplied by Lighting circuits do not require large currents. Typically, a circuit breaker customers with services which meet their needs (for voltage is stepped down at transformers to a more suitable At the house, a main fuse and meter are installed. or fuse of 6 amps is used. The conductors in lighting cables therefore independent radial circuits which are not connected to any other appliance. E Earth N Neutral need not be very thick. One 100 Watt bulb uses less than half an amp as The most common are immersion (water) heaters, cookers and electric example, budget accounts, direct debit and other payment NNeutral lower value. A two-wire cable is used to bring electricity to shown below. showers. Cookers and showers require very thick conductors. options) and with appropriate advice to help them use How is electricity distributedFig. 5in A the ring house?circut with four sockets the home. The neutral is connected to a metal plate in the Fuse or mcWhatb L Live is ESB Customer Supply? electricity more efficiently while saving money at the IV = Power 0.45 A x 220V = 100 W The cable is then terminated on a consumer unit. From the consumer unit Why use fuses and mcbs? same time. ground, and so is at 0V. Therefore, the neutral is said to be Socket 1 Socket 2 Fig.3 Lighting circut, two two-way switches different circuits are run to the various points where electricity is needed ESB Customer Supply supplies electricityA fuse is to a wire 1.8 that million will get hot and melt (“blow”) if the circuit is above its earthed. The voltage on the live wire alternates to 311V above Other- lights, sockets, circuits cookers etc. These circuits are all fed with the 220V from Therefore, a 6 amp mcb couldN safelyNeutra lprotect a circuit feeding more than ESB Customer Supply employs approximately 650 people ten 100 W bulbs. In practice,customers the lighting circuits (on the for a number basis of of rooms published are tariffs).rated current. It By provides melting, the fuse disconnects the live wire from the load, the consumer unit, so all domestic circuits are in parallel. Fuse or mcb and in any one year issues 11 million bills and handles over and below this 50 times a second giving an effective 220V. Lighting circuits do not require large currents. Typically, a circuit breaker Other types of domestic load use large currents and are suppliedconnected by in parallel andL Livesupplied through one mcb. It is not convenient reducing the risk of overheating and fire. The live wire connection to every circuit is fed through a safety device N Neutral customers with services which meet their needs (for 3 million telephone calls from customers. or fuse of 6 amps is used. The conductors in lighting cables therefore independent radial circuits which are not connected to any other appliance.to have all lights fail at the same time so it is common to have two or more Like a fuse, a miniature circuit breaker disconnects the live wire if the At the house, a main fuse and meter are installed. which cuts off the circuit if the current demanded becomes excessive. This E Earth lighting circuits in a house.example, budget accounts, direct debit andcurrent other is too payment large. It is a switch with contacts that open very quickly. need not be very thick. One 100 Watt bulb uses less than half an amp as Thecan bemost a fuse common or a miniature are circuit immersion breaker (mcb).(water) heaters, cookers and electric As a business unit within ESB, Customer Supply has over shown below. showers. Cookers and showers require very thick conductors. options) and with appropriate advice Circuit to help breakers them are faster use and more precise than fuses and they can be 75 years experience in providing electricity services to reset. The circuit breakers on a distribution board are very compact and How is electricity distributed in the house? Power circuits for appliances (sockets) customers throughout Ireland. Fuse or mcb L Live electricity more efficiently while savingare called money miniature at circuit the breakers. IV = Power 0.45 A x 220V = 100 W The cable is then terminated on a consumer unit. From the consumer unit Why use fuses and mcbs? The term appliance is asame general time. term for any thing powered through a Ireland has one of the fastest-growing electricity markets in Socket 1 Socket 2 plug and a flexible cable. The standard plug is designed to carry up to 13 different circuits are run to the various points where electricity is needed amps, though most appliances need considerably less. Inside the plug What is a residual current device (RCD)? the developed world. It grew over 40 per cent over the last N Neutral A fuse is a wire that will get hot and melt (“blow”) if the circuit is above its - lights, sockets, cookers etc. These circuits are all fed with the 220V from Therefore, a 6 amp mcb could safely protect a circuit feeding more than there is a fuse. The fuseESB is usually Customer either a 3-amp Supply fuse (for employs appliances upapproximately 650 people 10 years, far ahead of average growth in the rest of Europe. rated current. By melting, the fuse disconnects the live wire from the load, One device that reduces the likelihood of harm from electric shock is the RCD. the consumer unit, so all domestic circuits are in parallel. ten 100 W bulbs. In practice, the lighting circuits for a number of rooms are to 660 Watts) or a 13-amp fuse (for appliances up to almost 3 kilowatts). Electricity enters and leaves a house through the live and neutral wires. The market has been fully opened to competition since Fuse or mcb L Live reducing the risk of overheating and fire. and in any one year issues 11 million bills and handles over connected in parallel and supplied through one mcb. It is not convenient Where a 3-amp fuse is sufficient it should be used. A fault then is more Normally, the amount of electricity entering is matched by exactly the February 2005. The live wire connection to every circuit is fed through a safety device likely to blow this fuse only,3 million rather than telephone both blow it callsand also from trip the customers. mcb toN haveNeutra alll lights fail at the same time so it is common to have two or more Two-way switch same amount leaving. If there is a fault however, it often involves some Like a fuse, a miniature circuit breaker disconnects the live wireon ifthe the consumer Fuse unit. orSocket mcb L1LiveSocket 2 Socket 3 Socket 4 which cuts off the circuit if the current demanded becomes excessive. This lighting circuits in a house.E Earth electricity from a live wire going to earth, possibly through a person. This current is too large. It is a switch with contacts that open very quickly. As a business unit within ESB, Customeris calledSupply a residual has current over or an earth-leakage current. You can find out more about ESB Customer Supply by logging can be a fuse or a miniature circuit breaker (mcb). In general, almost all the powerNNeutra consumedl in a house is converted into onto www.esb.ie and www.sciencetechnologyaction.com Circuit breakers are faster and more precise than fuses and they Fcanuse orbe mc b LLive heat. Appliances that generate75 years a lot of experience heat, like electric in fires providing or kettles, electricityA fault current services to earth has to implications. Even 100 mA can cause a fire. An Power circuits for appliances (sockets) reset. The circuit breakersFig.1 on Imagea distribution of consumer board unit and are meter very compactuse largeand currents and consume a lot of power. At 220V, the current per even smaller current, 30 mA, can kill a person. are called miniature circuit breakers. kilowatt is about 4.5 amps.customers Many other throughout appliances such Ireland. as radios or The RCD consists of a circuit breaker which is tripped if the currents The term appliance is a general term for any thing powered through a The conductors in the circuit are copper and are insulated. The resistance mobile phone chargers need little power. must be low enough that, E Earth N NeutraIrelandl has one of the fastest-growing electricityentering and markets leaving on inthe live and neutral wires differ by more than 30 Be careful with electricity plug and a flexible cable. The standard plug is designed to carry up to 13 When sockets are fitted as shown below, the circuit is called a radial circuit. mA. Domestic RCDs will usually also trip if a certain current, for example • at the rated current, the drop in voltage between the consumer unit (It radiates out from the consumer unit.) Because each socket can supply amps, though most appliances need considerably less. Inside the plug What is a residual current device (RCD)? the developed world. It grew over 40 per63 cent A, is exceeded. over the last ‘Electricity is so much a part of modern living that we can often and the load is low 13 amps there is a limit to the number of sockets that can be supplied by take it for granted. It is a powerful and versatile energy but can be there is a fuse. The fuse is usually either a 3-amp fuse (for appliances up One device that reduces the likelihood of harm from electric shock is theone RCD. cable. 10 years, far ahead of average growth in Thethe current rest offor Europe.most or all of the circuits in modern houses is fed via an • the copper does not get too hot. dangerous if not used properly.’ to 660 Watts) or a 13-amp fuse (for appliances up to almost 3 kilowatts). RCD which is between the main fuse and their mcbs or fuses. ElectricityCables with largeenters diameters and leaves have less a houseresistance through than those the with live smaller and neutral wires. The market has been fully opened to competition since Fig.4 A radial circut with two sockets Where a 3-amp fuse is sufficient it should be used. A fault then is more Normally,diameters. In the general, amount domestic of electricitycircuits are classified entering as islighting matched circuits by exactly the Serious accidents with electricity in the home are rare but each year February 2005.Socket 1 Socket 2 likely to blow this fuse only, rather than both blow it and also trip the mcb sameor power amount circuits. leaving. If there is a fault however, it often involves some What is the earth rod? there is a small number of fatalities and serious injuries. Most of Fuse or mcb LLive Two-way switch on the consumer unit.Socket 1 Socket 2 Socket 3 Socket 4 electricity from a live wire going to earth, possibly through a person. This the accidents that occur are due either to carelessness or to a lack The earth wire in a domestic circuit is connected to an earth electrode in of awareness of some basic rules that should always be observed How lighting circuits are connected Fuse or mcYoub canL Live find out more about ESB Customer Supply by logging In general, almost all the power consumed in a house is converted into is called a residual current or an earth-leakage current. the ground which provides a low-resistance path via the ground itself to when using electricity.’ NNeutral N Neutral onto www.esb.ie and www.sciencetechnologyaction.com Fuse or mcb Two simple lighting circuits are shown below. The first circuit is used where the transformer. At the transformer, the neutral is connected to a plate in heat. AppliancesLLive that generate a lot of heat, like electric fires or kettles, E Earth Athere fault is acurrent single switch, to earth usually has at implications. the door of a room. Even 100 mA can cause a fire. An the ground. This is why electricity will flow from live to earth. The above is an extract from the booklet The Safe Use of Electricity Fig.1 Image of consumer unit and meter use large currents and consume a lot of power. At 220V, the current per even smaller current, 30 mA, can kill a person. in the Home which is produced by the ESB in cooperation with the kilowatt is about 4.5 amps. Many other appliances such as radios or Fuse or mcb L Live Electro Technical Council of Ireland. The booklet contains essential An alternative approach is the ring circuit. Here the circuit takes the form The RCD consists of a circuit breaker which is tripped if the currents information on electrical safety in general and also hints and rules The conductors in the circuit are copper and are insulated. The resistance mobile phone chargers need little power. of a ring with both ends of the ring connected to the consumer unit. Both which you should always follow. must be low enough that, E Earth N Neutral entering and leaving NonNeutra thel live and neutral wires differ by more “live”than wires30 are connectedBe to onecareful mcb, both neutrals with to electricitythe neutral, both When sockets are fitted as shown below, the circuit is called a radial circuit. mA. Domestic RCDs will usually also trip if a certain current, for exampleearths to earth. This has the advantage that the current demanded can • at the rated current, the drop in voltage between the consumer unit (It radiates out from the consumer unit.) Because each socket can supply The booklet is available on www.esb.ie. 63 A, is exceeded. flow two ways and is spread‘Electricity over two is so conductors. much a A part ring circuit of modern can living that we can often and the load is low 13 amps there is a limit to the number of sockets that can be supplied by Fig.2 Lighting circut, one switch contain more sockets than two radial circuits. take it for granted. It is a powerful and versatile energy but can be one cable. The current for most or all of the circuits in modern houses is fed via an • the copper does not get too hot. dangerous if not used properly.’ RCD which is between the main fuse and their mcbs or fuses. Cables with large diameters have less resistance than those with smaller Fig.4 A radial circut with two sockets Socket 1 Socket 2 Socket 3 Socket 4 diameters. In general, domestic circuits are classified as lighting circuits Serious accidents with electricity in the home are rare but each year Socket 1 Socket 2 or power circuits. What is the earth rod? Fuse or mcb LLivethere is a small number of fatalities and serious injuries. Most of the accidents that occur are due either to carelessness or to a lack The earth wire in a domestic circuit is connected to an earth electrode in of awareness of some basic rules that should always be observed How lighting circuits are connected Fuse or mcb L Live the ground which provides a low-resistance path via the ground itself to when using electricity.’ Two simple lighting circuits are shown below. The first circuit is used where N Neutral the transformer. At the transformer, the neutral is connected to a plate in E Earth N Neutral E Earth the ground. This is why electricity will flow from live to earth. there is a single switch, usually at the door of a room. Fuse or mcb LLive Two-way switch The above is an extract from the booklet The Safe Use of Electricity in the Home which is produced by the ESB in cooperation with the Fuse or mcb L Live NNeutral Electro Technical Council of Ireland. The booklet contains essential An alternative approach is the ring circuit. Here the circuit takes the form information on electrical safety in general and also hints and rules of a ring with both ends of the ring connected to the consumer unit. Both which you should always follow. N Neutral “live” wires are connected to one mcb, both neutrals to the neutral, both earths to earth. This has the advantage that the current demanded can The booklet is available on www.esb.ie. flow two ways and is spread over two conductors. A ring circuit can Fig.2 Lighting circut, one switch contain more sockets than two radial circuits.
Socket 1 Socket 2 Socket 3 Socket 4 Socket 1 Socket 2
Fuse or mcb Fuse or mcb LLive L Live N Neutral E Earth
E Earth N Neutral
Fuse or mcb LLive Two-way switch
NNeutral
Socket 1 Socket 2 Socket 3 Socket 4
Fuse or mcb LLive
E Earth N Neutral
Socket 1 Socket 2
Fuse or mcb L Live N Neutral E Earth
Socket 1 Socket 2 Socket 3 Socket 4
Fuse or mcb LLive
E Earth N Neutral Fuse or mcb L Live
FuseN Neutra or lmcb L Live
N Neutral
Fuse or mcb LLive Two-way switch
NNeutral
Socket 1 Socket 2
Fuse or mcb L Live N Neutral Fuse EorEarth mcb LLive Two-way switch
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Socket 1 Socket 2 Socket 3 Socket 4
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E Earth N Neutral
Socket 1 Socket 2
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The second circuit is used where there are two switches, for example at How is electricity supply delivered to each of two doors to a room. The type of switch used is called a two-way a house? switch and, if the light is off, as drawn, either switch will switch it on. If the Socket 1 Socket 2 Socket 3 Socket 4 light is on, either switch can switch it off. Examine the circuit and see why The ESB maintains a national network of high tension power this is so. Fuse or mcb LLive lines. The voltages on these lines are as high as 400 kV. Such voltages are not delivered to domestic premises. Instead the Fuse or mcb LLive Two-way switch voltageSyllabus is stepped Reference down at transformers to a more suitable Activities Examination Questions Biographical Notes E Earth N Neutral lower value. A two-wire cable is used to bring electricity to NNeutral • Energy saving devices make sense, look at the difference in running Fig.5 A ring circut with four sockets theLeaving home. TCertificatehe neutral is Physics: connected to a metal plate in the 2004 Higher Level What is ESB Customer Supply? Alessandro Volta ground, and so is at 0V. Therefore, the neutral is said to be costs for a CF and incandescent bulb. Electricity 7, Domestic circuits Fig.3 Lighting circut, two two-way switches Read the following passage andESB answer Customer the following Supply supplies questions. electricity to 1.8an million Italian physist famous as a pioneer in electricity. He was professor of earthed. The voltage on the live wire alternates to 311V above Other circuits • If you are watching the light from a lamp when a kettle, or something customers (on the basis of published tariffs). It providesphysics at the Royal School in Como and then at the University of Pavia. He andJunior below Certificate this 50 times Science: a second giving an effective 220V. Other types of domestic load use largeYour currents home and is aresupplied supplied with by electricity at 230 volts, 50 Hertz. At the electrical Lighting circuits do not requireelse, largeis also currents. switched Typically, on, aa circuitsmall breaker reduction in brightness may be seen. customers with services which meet their needsinvented (for the electrophorus in 1775, an instrument that produced charges independent radial circuits which are not connectedsupply intake to any other position appliance. is your main consumer unit or fuse board. At the AtSection the house, 3C5, a mainElectricity fuse and in meterthe home are installed. or fuse of 6 amps is used.Ohm’s The conductors law says inthat lighting if the cables current therefore through a resistance increases the of static electricity. He also developed the voltaic pile, a type of battery. In The most common are immersion (water) heaters, cookers and electric example, budget accounts, direct debit and other payment need not be very thick. Onevoltage 100 Watt across bulb uses it increases. less than half It seemsan amp asstrange to think of the conductors position you will find your main switch. Your sockets, immersion group and shown below. showers. Cookers and showers require very thick conductors. options) and with appropriate advice to help themhonour use of his work, Napoleon made him a Count in 1810. How is electricity distributed in the house? as a resistance but they are and the 220V supply in the house is bathroom heater (or shower) are protected by Residual Current Devices Fuse or mcb L Live electricity more efficiently while saving money at the IV = Power 0.45 A x 220V = 100 W (RCD) installed in your fuse board. These provide a high degree of safety The cable is then terminated on a consumer unit. From the consumer unit reduced by the voltage drop caused by the extraWhy current. use fuses and mcbs? same time. Socket 1 Socket 2 Georg Simon Ohm different circuits are run to the various points where electricity is needed on these circuits and it is important that they are tested at least every 3 A fuse is a wire that will get hot and melt (“blow”) if the circuit is above its - lights, sockets, cookers etc. These circuits are all fed with the 220V from Therefore, a 6 amp mcb• couldIn theN safely Neutra1950s, lprotect it was a circuitcommon feeding for amore rural than house with electricity to have electric months. The final circuits are protectedESB byCustomer Miniature Supply Circuit employs Breakers. approximately 650was people a German physicist, whilst working as a high school teacher, started rated current. By melting, the fuse disconnects the live wire from the load, the consumer unit, so all domestic circuits are in parallel. ten 100 W bulbs. In practice,lights, the lighting one socket circuits and,for a number possibly of rooms an electric are cooker. How has life changed Fuse or mcb L Live reducing the risk of overheating and fire. and in any one year issues 11 million bills and handleshis researchover with the recently invented electrochemical cell, invented by connected in parallel and insupplied the last through 50 years? one mcb. How It ismany not convenient sockets are there in your home? It is advisable to contact your local ESB about cheaper night tariffs, these The live wire connection to every circuit is fed through a safety device N Neutral 3 million telephone calls from customers. Italian Count Alessandro Volta. Using equipment of his own creation, Ohm to have all lights fail at the same time so it is common to have two or more Like a fuse, a miniature circuit breaker could disconnects make the significant live wire if savings the to your electricity bill. Storage heaters may whichLearning cuts off the circuit Objectives if the current demanded becomes excessive. This E Earth lighting circuits in a house. current is too large. It is a switch with contacts that open very quickly. determined that the current that flows through a wire is proportional to its can be a fuse or a miniature circuit breaker (mcb). • Consider the second lighting circuit which has two two-way switches. be used to avail of these cheaper rates.As a business unit within ESB, Customer Supply has over Circuit breakers are faster and more precise than fuses and they can be cross sectional area and inversely proportional to its length. This is Ohm’s On completing this section, the student should be able to: If a third (or even a fourth or fifth) switch is required, this is possible 75 years experience in providing electricity services to Power circuits forby inserting appliances a different (sockets) type of switch in the reset.circuit The between circuit breakers the two- on a distributionEach board plug are top very contains compact anda small cartridge fuse. Cartridge fuses are supplied law and can be written as V = IR where V is voltage, I is current and R is are called miniature circuit breakers. customers throughout Ireland. • Describe the ideas behind electricity distribution and use in way switches. This switch is called an intermediate switch. It has four with a rating of 1A, 2A, 3A, 5A and 13A. A fuse should never be replaced resistance. The term appliance is a general term for any thing powered through a Ireland has one of the fastest-growing electricity markets in the home plug and a flexible cable. Theterminals. standard You plug can is designed insert asto carry many up asto 13you wish. Can you guess what an by anything other than a suitable fuse. amps, though most appliances need considerably less. Inside the plug What is a residual current device (RCD)? the developed world. It grew over 40 per cent over the last intermediate switch does? (Adapted form ‘Home Safety’, Register of Electrical Contractors of Ireland. RECI) • Outline some safety aspects of using electricity there is a fuse. The fuse is usually either a 3-amp fuse (for appliances up One device that reduces the likelihood of harm from electric shock is the RCD. 10 years, far ahead of average growth in the rest ofAndre Europe. Marie Ampere to 660 Watts) or a 13-amp• Check fuse (for the appliances cable attachedup to almost to 3 ankilowatts). appliance. ItElectricity usually entershas three and leaves wires. a house through(a) Name the live and and giveneutral the wires. colour of theThe wire market that should has been be connected fully opened to tothe competition since • Identify different types of circuits and protective devices Where a 3-amp fuse is sufficient it should be used. A fault then is more a French physicist, is best known for defining a way to measure the flow of These are coloured brown, blue and green/yellowNormally,. Looking the amount into of electricitythe entering fuse is matched in a standard by exactly three-pin the plug.February (7) 2005. likely to blow this fuse only, rather than both blow it and also trip the mcb same amount leaving. If there is a fault however, it often involves some current, which was named after him, the ampere. He also laid the foundation • State the formula relating power, voltage and current Fuse or mcb plugLLive when the back is takenTwo-way off,switch there are three pins and a cord on the consumer unit.Socket 1 Socket 2 Socket 3 Socket 4 electricity from a live wire going to earth, (b)possibly Explain through why a replacingperson. This a fuse with a piece of aluminium for the science of electrodynamics. Among his accomplishments was grip visible. The green yellow earth wire is is connected called a residual to thecurrent pin or inan earth-leakage current. You can find out more about ESB Customer Supply by logging In general, almost all the powerNNeutra consumedl in a house is converted into foil is dangerous. (7) onto www.esb.ie and www.sciencetechnologyaction.comfiguring out a way to measure the strength of a magnetic field in relation Fuse or mcb LLive the top centre. The neutral wire is blue and connected to the pin on heat. Appliances that generate a lot of heat, like electric fires or kettles, A fault current to earth has implications. Even 100 mA can cause a fire. An to an electric current, known as Ampere’s theorem. Ampere’s law is a rule use large currents and consumethe left a lot (normally of power. markedAt 220V, the “N”). current The per pin on the right is the live pin (c) A table lamp has a power rating of 100W. What is the Fig.1 Image of consumer unit and meter even smaller current, 30 mA, can kill a person. that deals with the mutual interaction of current-carrying wires. kilowatt is about 4.5 amps.and Many it is other connected appliances to such a fuse. as radios The or other end of the fuse (normally most suitable fuse for the lamp? (7) The conductors in the circuit are copper and are insulated. The resistance mobile phone chargers needmarked little power. “L”) is connected to the brown live wire.The RCDWhen consists wiring of a circuitplug breaker which is tripped if the currents must be low enough that, E Earth N Neutral entering and leaving on the live and neutral(d) wires Some differ electrical by more thanappliances 30 are Besupplied careful with two-pinwith electricity plugs. When sockets are fitted asit shown is important below, the circuitthat theis called cord a radial grip circuit. grips the outermA. Domestic sheath RCDsand notwill usually just also trip if a certain current, for example You can find out more about these and other great • at the rated current, the drop in voltage between the consumer unit (It radiates out from the consumer unit.) Because each socket can supply Why is the earth wire not required in these devices? (7) the wires. Some appliances only have two 63 wires, A, is exceeded. brown and blue. ‘Electricity is so much a part of modern living that we can often and the load is low 13 amps there is a limit to the number of sockets that can be supplied by scientists at www.sciencetechnologyaction.com General Learning Points (e) Sketch a voltage-time graph of takethe 230Vit for granted. supply. It is(7) a powerful and versatile energy but can be one cable. Connect them as above. The current for most or all of the circuits in modern houses is fed via an • the copper does not get too hot. dangerous if not used properly.’ RCD which is between the main fuse and their mcbs or fuses. Cables• Small with large electric diameters currents have canless resistancekill. than those with smaller (f) Explain how a Residual Current Device (RCD) operates. (7) Fig.4 A radial circut with two sockets diameters. In general, domestic circuits are classified as lighting circuits Serious accidents with electricity in the home are rare but each year Socket 1 Socket 2 (g) Give one advantage of a Residual Current Device (RCD) or• power People circuits. conduct electricity. A typical person has a resistance of What is the earth rod? there is a small number of fatalities and serious injuries. Most of over a Miniature Circuit Breaker.the (MCB) accidents (7) that occur are due either to carelessness or to a lack between 1.5 kΩ and 5 kΩ. It varies with the individual and whether True or False The earth wire in a domestic circuit is connected to an earth electrode in Fuse or mcb of awareness of some basic rules that should always be observed Howthe lighting skin is wet circuits or not. are connected L Live the ground which provides a low-resistance(h) path Storage via the heaters ground itselfhave to a large heat capacity. Why? (7) Indicate whether the following are true (T) or false (F) when using electricity.’ Two simple lighting circuits are shown below. The first circuit is used where N Neutral the transformer. At the transformer, the neutral is connected to a plate in E Earth there• Evenis a single a current switch, usuallyas low at as the 7mA door ofcan a room. prevent the victim from letting go. by drawing a circle around T or F. the ground. This is why electricity will flowFor from furtherlive to earth. examples of pastThe paper above isexam an extract questions from the booklet check The Safe Use of Electricity out www.sciencetechnologyaction.comin the Home which is produced by the ESB in cooperation with the Fuse or mcb L Live (a) Fuses protect people from shocks T F Electro Technical Council of Ireland. The booklet contains essential • For a resistance of 1.5 kΩ the current would be about 150 mAAn alternative and approach is the ring circuit. Here the circuit takes the form information on electrical safety in general and also hints and rules from arm to arm through the heart. This is likely to be fatal. of a ring with both ends(b) of Your the ring electricity connected bill to charges the consumer for the unit. total Both voltage you have used T F which you should always follow. N Neutral “live” wires are connected to one mcb, both neutrals to the neutral, both earths to earth. This (c)has Thethe advantage green/yellow that the wire current in a plugdemanded goes canto the earth pin at the top T F Revise the Terms • Fuses do not protect people from shocks, the current required to kill The booklet is available on www.esb.ie. flow two ways and is spread over two conductors. A ring circuit can Did You Know? a person is much lower than the rating of any household fuse. (d) A two-way switch is needed to light two bulbs at the same time Fig.2 Lighting circut, one switch contain more sockets than two radial circuits. T F Can you recall the meaning of these terms? Revising the • For simplicity, no earth wire was shown in the lighting circuits but (e) A 6A fuse can cater for 10 100W bulbs T F • When the State was founded in 1922, hundreds of small electricity terminology is a powerful aid for recall and retention. schemes existed. These provided limited electricity supply in cities metal light fittings must be earthed. (f) PeopleSocket 1 areSocket good 2 S ocketinsulators 3 Socket 4 T F and towns. Transformers; neutral; earthed; live; consumer unit; parallel; fuse; • Most electricity is converted into heat. Where a lot of heat is generated, (g) When switched on, a kettle uses less electricity than a 100W T F Fuse or mcb LLive miniature circuit breaker (mcb); insulated; resistance; load; lighting circuits; bulb (the bulb is obviously much hotter). • There was also a proposal to dam the river Shannon near Limerick and a lot of electricity (energy) is consumed. power circuits; two-way switch; appliance; radial; ring; residual current; build a hydro-electric electricity station. The government appointed (h) All domestic circuits are in series T F earth-leakage current; electrode • 220 V is an effective mean, the peak voltage is 311 V (220 x √2) Siemens, a German engineering firm, to provide a detailed scheme for because the neutral is earthed it is at 0V. E Earth(i) N ModernNeutral supplies will cut off if an earth-leakage of 50 mA is T F this. The work was started in 1925. detected Check the Glossary of Terms for this lesson at Fuse or mcb LLive Two-way switch www.sciencetechnologyaction.com (j) The fuse in a plug is in series with the live wire T F • This was a giant project and associated with it was a vision of a properly NNeutral planned and organised electricity supply needed for the development (k) A 6A fuse can cater for a 2.5 kW kettle T F of the new State. (l) Big fuses are best because they blow less often T F • Legislation was passed to create the organisation to do this and the Check your answers to these questions on ESB was formed in 1927. It gradually took over the major existing www.sciencetechnologyaction.com suppliers and created an essential national electricity supply body.
Socket 1 Socket 2
Fuse or mcb L Live N Neutral E Earth
Socket 1 Socket 2 Socket 3 Socket 4
Fuse or mcb LLive
E Earth N Neutral Fuse or mcb L Live
FuseN Neutra or lmcb L Live
N Neutral
Fuse or mcb LLive Two-way switch
NNeutral
Socket 1 Socket 2
Fuse or mcb L Live N Neutral Fuse EorEarth mcb LLive Two-way switch
NNeutral
Socket 1 Socket 2 Socket 3 Socket 4
Fuse or mcb LLive
E Earth N Neutral
Socket 1 Socket 2
Fuse or mcb L Live Fuse or mcb L Live N Neutral E Earth N Neutra l Electricity in Home the Electricity in Home the
The second circuit is used where there are two switches, for example at How is electricity supply delivered to each of two doors to a room. The type of switch used is called a two-way a house? switch and, if the light is off, as drawn, either switch will switch it on. If the Socket 1 Socket 2 Socket 3 Socket 4 light is on, either switch can switch it off. Examine the circuit and see why The ESB maintains a national network of high tension power this is so. Fuse or mcb LLive lines. The voltages on these lines are as high as 400 kV. Such
voltages are not delivered to domestic premises. Instead the Fuse or mcb LLive Two-way switch Syllabus Reference Activities Examinationvoltage is stepped down Questions at transformers to a more suitable Biographical Notes E Earth N Neutral lower value. A two-wire cable is used to bring electricity to NNeutral • Energy saving devices make sense, look at the difference in running Fig.5 A ring circut with four sockets Leaving Certificate Physics: 2004the home. Higher The neutral Level is connected to a metal plate in the Alessandro Volta What is ESB Customer Supply? costs for a CF and incandescent bulb. ground, and so is at 0V. Therefore, the neutral is said to be Electricity 7, Domestic circuits Read the following passage and answer the following questions.Fig.3 Lighting circut,an two Italian two-way physist switches famous as a pioneer in electricity. He was professor of ESB Customer Supply supplies electricity to 1.8 million earthed. The voltage on the live wire alternates to 311V above Other circuits • If you are watching the light from a lamp when a kettle, or something physics at the Royal School in Como and then at the University of Pavia. He customers (on the basis of published tariffs). It provides Junior Certificate Science: Yourand belowhome isthis supplied 50 times with a electricitysecond giving at 230 an volts, effective 50 Hertz. 220V. At the electrical Other types of domestic load use large currents and are supplied by else, is also switched on, a small reduction in brightness may be seen. Lighting circuits do inventednot require thelarge electrophorus currents. Typically, in a1775, circuit anbreaker instrument that produced charges customers with services which meet their needs (for supply intake position is your main consumer unit or fuse board. At the independent radial circuits which are not connected to any other appliance. Section 3C5, Electricity in the home Ohm’s law says that if the current through a resistance increases the At the house, a main fuse and meter are installed. or fuse of 6 amps isof used.static The electricity. conductors He in also lighting developed cables therefore the voltaic pile, a type of battery. In The most common are immersion (water) heaters, cookers and electric example, budget accounts, direct debit and other payment voltage across it increases. It seems strange to think of the conductors position you will find your main switch. Your sockets, immersion groupneed and not be very thick. One 100 Watt bulb uses less than half an amp as shown below. honour of his work, Napoleon made him a Count inshowers. 1810. Cookers and showers require very thick conductors. options) and with appropriate advice to help them use as a resistance but they are and the 220V supply in the house is bathroomHow is electricityheater (or shower) distributed are protected in the by Residualhouse? Current Devices Fuse or mcb L Live electricity more efficiently while saving money at the (RCD) installed in your fuse board. These provide a high degree of safety IV = Power 0.45 A x 220V = 100 W reduced by the voltage drop caused by the extra current. The cable is then terminated on a consumer unit. From the consumer unit Why use fuses and mcbs? same time. Georg SimonSocket Ohm 1 Socket 2 ondifferent these circuits circuits are runand to itthe is various important points thatwhere they electricity are testedis needed at least every 3 A fuse is a wire that will get hot and melt (“blow”) if the circuit is above its • In the 1950s, it was common for a rural house with electricity to have electric months.- lights, sockets, The fi cookersnal circuits etc. These are protectedcircuits are all by fed Miniature with the 220V Circuit from Breakers.Therefore, a 6 amp wasmcb coulda GermanN safelyNeutra lprotectphysicist, a circuit whilst feeding working more than as a high school teacher, started ESB Customer Supply employs approximately 650 people rated current. By melting, the fuse disconnects the live wire from the load, lights, one socket and, possibly an electric cooker. How has life changed the consumer unit, so all domestic circuits are in parallel. ten 100 W bulbs. In practice, the lighting circuits for a number of rooms are Fuse or mcbhis LresearchLive with the recently invented electrochemicalreducing cell,the risk invented of overheating by and fire. and in any one year issues 11 million bills and handles over in the last 50 years? How many sockets are there in your home? It is advisable to contact your local ESB about cheaper night tariffs,connected these in parallel and supplied through one mcb. It is not convenient The live wire connection to every circuit is fed through a safety device N Neutral Italian Count Alessandro Volta. Using equipment of his own creation, Ohm 3 million telephone calls from customers. could make significant savings to your electricity bill. Storage heatersto have may all lights fail at the same time so it is common to have two or more Like a fuse, a miniature circuit breaker disconnects the live wire if the Learning Objectives which cuts off the circuit if the current demanded becomes excessive. This E Earth lighting circuits in a determinedhouse. that the current that flows through a wirecurrent is proportional is too large. It isto aits switch with contacts that open very quickly. • Consider the second lighting circuit which has two two-way switches. becan used be a fuse to availor a miniature of these circuit cheaper breaker rates. (mcb). As a business unit within ESB, Customer Supply has over cross sectional area and inversely proportional to Circuitits length. breakers This are is faster Ohm’s and more precise than fuses and they can be On completing this section, the student should be able to: If a third (or even a fourth or fifth) switch is required, this is possible 75 years experience in providing electricity services to by inserting a different type of switch in the circuit between the two- Each plug top contains a small cartridge fuse. Cartridge fuses are suppliedPower circuitslaw andfor canappliances be written as (sockets) V = IR where V is voltage,reset. I Theis current circuit breakers and R onis a distribution board are very compact and are called miniature circuit breakers. customers throughout Ireland. • Describe the ideas behind electricity distribution and use in way switches. This switch is called an intermediate switch. It has four with a rating of 1A, 2A, 3A, 5A and 13A. A fuse should never be replaced resistance. The term appliance is a general term for any thing powered through a Ireland has one of the fastest-growing electricity markets in the home terminals. You can insert as many as you wish. Can you guess what an by anything other than a suitable fuse. plug and a flexible cable. The standard plug is designed to carry up to 13 amps, though most appliances need considerably less. Inside the plug What is a residual current device (RCD)? the developed world. It grew over 40 per cent over the last intermediate switch does? (Adapted form ‘Home Safety’, Register of Electrical Contractors of Ireland. RECI) • Outline some safety aspects of using electricity there is a fuse. The Andrefuse is usually Marie either a Ampere 3-amp fuse (for appliances up One device that reduces the likelihood of harm from electric shock is the RCD. 10 years, far ahead of average growth in the rest of Europe. • Check the cable attached to an appliance. It usually has three wires. (a) Name and give the colour of the wire that should be connectedto to660 the Watts) or a 13-amp fuse (for appliances up to almost 3 kilowatts). Electricity enters and leaves a house through the live and neutral wires. The market has been fully opened to competition since • Identify different types of circuits and protective devices Where a 3-amp fusea isFrench sufficient physicist, it should beis bestused. knownA fault then for definingis more a way to measure the flow of These are coloured brown, blue and green/yellow. Looking into the fuse in a standard three-pin plug. (7) Normally, the amount of electricity entering is matched by exactly the February 2005. likely to blow this fusecurrent, only, rather which than was both named blow it andafter also him, trip the the ampere.mcb Hesame also amount laid the leaving. foundation If there is a fault however, it often involves some • State the formula relating power, voltage and current plug when the back is taken off, there are three pins and a cord Fuse or mcb LLive Two-way switch (b) Explain why replacing a fuse with a piece of aluminium on the consumer unit.forSocket the 1 scienceSocket 2 Socket of electrodynamics. 3 Socket 4 Among his electricity accomplishments from a live wire was going to earth, possibly through a person. This grip visible. The green yellow earth wire is connected to the pin in is called a residual current or an earth-leakage current. You can find out more about ESB Customer Supply by logging foil is dangerous. (7) In general, almost allfiguring the powerNNeutra out consumed l a way to in measurea house is theconverted strength into of a magnetic field in relation onto www.esb.ie and www.sciencetechnologyaction.com the top centre. The neutral wire is blue and connected to the pin on Fuse or mcb LLive heat. Appliances thatto generatean electric a lot current, of heat, like known electric as fires Ampere’s or kettles, theorem. A faultAmpere’s current tolaw earth is hasa rule implications. Even 100 mA can cause a fire. An the left (normally marked “N”). The pin on the right is the live pin (c) A table lamp has a power rating of 100W. What is the use large currents and consume a lot of power. At 220V, the current per Fig.1 Image of consumer unit and meter that deals with the mutual interaction of current-carryingeven smaller wires. current, 30 mA, can kill a person. and it is connected to a fuse. The other end of the fuse (normally most suitable fuse for the lamp? (7) kilowatt is about 4.5 amps. Many other appliances such as radios or marked “L”) is connected to the brown live wire. When wiring a plug The conductors in the circuit are copper and are insulated. The resistance mobile phone chargers need little power. The RCD consists of a circuit breaker which is tripped if the currents (d)must Some be low electricalenough that, appliances are supplied with two-pin plugs. E Earth N Neutral entering and leaving on the live and neutral wires differ by more than 30 Be careful with electricity it is important that the cord grip grips the outer sheath and not just When sockets are fitted as Youshown can below, find the circuit out is morecalled a radialabout circuit. these andmA. Domestic other RCDsgreat will usually also trip if a certain current, for example • atWhy the ratedis the current, earth thewire drop not in required voltage between in these the devices?consumer unit(7) (It radiates out from the consumer unit.) Because each socket can supply the wires. Some appliances only have two wires, brown and blue. 63 A, is exceeded. ‘Electricity is so much a part of modern living that we can often and the load is low 13 amps there is a limit to thescientists number of sockets at www.sciencetechnologyaction.com that can be supplied by General Learning Points (e) Sketch a voltage-time graph of the 230V supply. (7) take it for granted. It is a powerful and versatile energy but can be Connect them as above. one cable. The current for most or all of the circuits in modern houses is fed via an • the copper does not get too hot. dangerous if not used properly.’ RCD which is between the main fuse and their mcbs or fuses. • Small electric currents can kill. (f)Cables Explain with large how diameters a Residual have lessCurrent resistance Device than (RCD) those with operates. smaller (7) Fig.4 A radial circut with two sockets diameters. In general, domestic circuits are classified as lighting circuits Serious accidents with electricity in the home are rare but each year (g) Give one advantage of a Residual Current Device (RCD) Socket 1 Socket 2 • People conduct electricity. A typical person has a resistance of or power circuits. What is the earth rod? there is a small number of fatalities and serious injuries. Most of over a Miniature Circuit Breaker. (MCB) (7) the accidents that occur are due either to carelessness or to a lack between 1.5 kΩ and 5 kΩ. It varies with the individual and whether True or False The earth wire in a domestic circuit is connected to an earth electrode in Fuse or mcb of awareness of some basic rules that should always be observed the skin is wet or not. (h)How Storage lighting heaters circuits have a large are heatconnected capacity. Why? (7) L Live the ground which provides a low-resistance path via the ground itself to Indicate whether the following are true (T) or false (F) when using electricity.’ Two simple lighting circuits are shown below. The first circuit is used where N Neutral the transformer. At the transformer, the neutral is connected to a plate in E Earth • Even a current as low as 7mA can prevent the victim from letting go. by drawing a circle around T or F. Forthere isfurther a single switch, examples usually at ofthe pastdoor of papera room. exam questions check the ground. This is why electricity will flow from live to earth. The above is an extract from the booklet The Safe Use of Electricity out www.sciencetechnologyaction.com in the Home which is produced by the ESB in cooperation with the (a) Fuses protect people from shocks T F Fuse or mcb L Live Electro Technical Council of Ireland. The booklet contains essential • For a resistance of 1.5 kΩ the current would be about 150 mA and An alternative approach is the ring circuit. Here the circuit takes the form information on electrical safety in general and also hints and rules from arm to arm through the heart. This is likely to be fatal. (b) Your electricity bill charges for the total voltage you have used of a ring with both ends of the ring connected to the consumer unit. Both T F which you should always follow. N Neutral “live” wires are connected to one mcb, both neutrals to the neutral, both (c) The green/yellow wire in a plug goes to the earth pin at the top T F earths to earth. ThisRevise has the advantage the that Terms the current demanded can • Fuses do not protect people from shocks, the current required to kill The booklet is available on www.esb.ie. Did You Know? flow two ways and is spread over two conductors. A ring circuit can a person is much lower than the rating of any household fuse. (d) A two-way switch is needed to light two bulbs at the same time T F Fig.2 Lighting circut, one switch contain more socketsCan than youtwo radial recall circuits. the meaning of these terms? Revising the • For simplicity, no earth wire was shown in the lighting circuits but (e) A 6A fuse can cater for 10 100W bulbs T F • When the State was founded in 1922, hundreds of small electricity terminology is a powerful aid for recall and retention. schemes existed. These provided limited electricity supply in cities metal light fittings must be earthed. (f) People are good insulators T F Socket 1 Socket 2 Socket 3 Socket 4 and towns. Transformers; neutral; earthed; live; consumer unit; parallel; fuse; • Most electricity is converted into heat. Where a lot of heat is generated, (g) When switched on, a kettle uses less electricity than a 100W T F Fuse or mcb miniatureLLive circuit breaker (mcb); insulated; resistance; load; lighting circuits; bulb (the bulb is obviously much hotter). • There was also a proposal to dam the river Shannon near Limerick and a lot of electricity (energy) is consumed. power circuits; two-way switch; appliance; radial; ring; residual current; build a hydro-electric electricity station. The government appointed (h) All domestic circuits are in series T F earth-leakage current; electrode • 220 V is an effective mean, the peak voltage is 311 V (220 x √2) Siemens, a German engineering firm, to provide a detailed scheme for because the neutral is earthed it is at 0V. (i) Modern supplies will cut off if an earth-leakage of 50 mA is T F this. The work was started in 1925. E Earth N Neutral detected Check the Glossary of Terms for this lesson at Fuse or mcb LLive Two-way switch www.sciencetechnologyaction.com (j) The fuse in a plug is in series with the live wire T F • This was a giant project and associated with it was a vision of a properly planned and organisedNNeutral electricity supply needed for the development (k) A 6A fuse can cater for a 2.5 kW kettle T F of the new State. (l) Big fuses are best because they blow less often T F • Legislation was passed to create the organisation to do this and the Check your answers to these questions on ESB was formed in 1927. It gradually took over the major existing www.sciencetechnologyaction.com suppliers and created an essential national electricity supply body.
Socket 1 Socket 2
Fuse or mcb L Live N Neutral E Earth
Socket 1 Socket 2 Socket 3 Socket 4
Fuse or mcb LLive
E Earth N Neutral