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Science Interactive LTD Copyright 2005

Science base multimedia CD-ROM for PC is a collection of 38 units or tools totalling over 1150

PowerPoint slides. Each unit covers a wide range of different delivery and learning styles, offering an

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learning are supported through use of high quality images, graphics, challenging exercises andquestions. Units can be used in the classroom via an interactive whiteboard, data projector or used

during individual study via a PC or school network.

Unit 19: The Transitional Metals

Unit 18: Metals and their Properties

Unit 17: The Alkali Metals

Unit 16: The Periodic Table and its Elements

Unit 15: Genetic Engineering

Unit 14: Evolution and Human Impact

Unit 13: Inheritance and Selection

Unit 12: Mitosis and Meiosis

Unit 11: Flow of Energy and Elements through the Environment

Unit 10: Water Transport in Plants

Unit 9: Photosynthesis in Green Plants

Unit 8: Drugs and Bad Body Maintenance

Unit 7: Hormones and the Endocrine System

Unit 6: Human Homeostasis

Unit 5: Nervous System and the Senses

Unit 4: The Respiratory System

Unit 3: Healthy Body and Immunity

Unit 2: The Circulatory System

Unit 1: The Digestive System

Unit 38: Cells, Tissue, Organs and Organs systems

Unit 37: Natural Forces

Unit 36: Sound and Hearing

Unit 35: The Alkaline Earth Metals

Unit 34: The Earth and Plate Tectonics

Unit 33: Earth and Space

Unit 32: Newton's Forces and the Effects of Forces

Unit 31: Radioactivity

Unit 30: Light and the Electromagnetic Spectrum

Unit 29: Electricity

Unit 28: Generating Electricity and its Domestic Use

Unit 27: Energy

Unit 26: Rates of Reaction

Unit 25: The Noble Gases, their Properties and Uses

Unit 24: The Halogens, their Uses and Compounds

Unit 23: Ionic and Covalent Compounds

Unit 22: Elements, Molecules and Compounds

Unit 21: Rock Cycle

Unit 20: Crude Oil and its Products




Unit 28

Generating Electricity and its Domestic Use



Unit 28: Generating Electricity and its Domestic UseUnit 28: Generating Electricity and its Domestic Use Science Interactive LTD Copyright 2005

Understand: Keywords:

1. What is electricity and that electricity is a ‘flowof current’ around a conducting material.

2. The main uses of electricity in the home.

3. How domestic electricity is generated to meetsupply and demand.

4.How fossil and nuclear fuels are used togenerate electricity for residential, commercialand industrial users.

5. The contributions of combusting fossil fuels toacid rain and the greenhouse effect.

6. That there are many renewable forms of energythat can be used as an alternative to fossilfuels.

7. How to induce a current in a conductingmaterial and how do turbine generatorsproduce electricity

8. The role of power companies and the nationalgrid in distributing electricity to all users.

9. The difference between AC and DC electricity.

10. How voltage is transformed during its transportfrom producer to user.

11. How do electricity companies charge for our use and the dangers of using electricity.

Electricity, Energy, Current, Voltage, Watts,

Power, Joules, Generator, Fossil fuels,

Renewable, Turbine Power station,

Transformer, Pylons, Cables, Plug, Fuse,

Appliance, Electromagnetism, Dynamo,

Motor, Earthing, Circuit Breaker, Turbine,Acid rain, Greenhouse effect, Global warming

& Electrocution.

web: www.science-interactive.co.uk email: sales science-interactive.co.ukScience Interactive LTD PO BOX 50764 LONDON NW6 9AT

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Combusting fossil fuels like c_____, and natural gas produces h______ energy which

is used to produce super hot steam. The steam drives the turbines which are made

from huge magnets surrounded by a copper coil. The movement of the copper coilacross a magnetic field induces a c________ flow in the copper wire. Electrical energy

cannot be stored and is delivered instantly by the National Grid using a network of

overhead wires and underground cables clean and e fficiently to every home in Great

Britain.

Supplying the nation’s electricity:

Electricity at the flick of a switchElectricity at the flick of a switchScience Interactive LTD Copyright 2005

Word bank: coal heat current

The amount of electricity

that you use during a

year is calculated using

meter readings. Electricalenergy in the home can

be transformed into many

other forms of energy.

Customer

Electricity is then

transported along a huge

network of underground

or over ground copper cables to various users

including schools, homes

and factories.

Transmission

Notes

Diagram

Non-renewable fossil

fuels containing ‘ancient

energy’ is extracted

from deep underground.These fuels include

crude oil, natural gas

and coal.

Fuel

Combusting fossil fuels

generates large amounts

of heat energy which in

turn boils water producing steam. This

drive turbines producing

electricity.

Power station





Energy use in the homeEnergy use in the homeEnergy supplied to homes, schools, hospitals and industry needs to be immediate and reliable.

The national grid supplies electrical energy at the flick of a s_________. Demand for electrical

energy varies during the day, with peak demands in the morning, during working hours andearly evening. The lowest demand is during the n________. Power companies use reliable

sources of energy like nuclear power to maintain a steady supply. When the demand is high,

they can use energy produced by gas fired or hydroelectric power stations. These can be started

relatively quickly and cope with ‘ peak demands.’ When are these peak periods likely to occur ?

Electricity use in the home: Word bank: switch night

The percentage of energy used in homes, offices and other building varies over the year. In the

winter the majority of energy is used for home heating and lighting. In the summer there is

less demand because of the warm temperatures and long light evenings.

Notes:

4%

Cooking

7%47%42%

Diagram

Heating Lighting Other





Electrical power and the light bulbElectrical power and the light bulb oneone

Most of the electrical energy supplied to homes is used for lighting. The filament light bulb was invented

and patented by Thomas Edison in 1880. Edison knew that an electric current that flowed through a

filament would glow to provide a light source. He also noted that the thinner the wire, the more light would be produced. The only problem was finding the right material to make a filament that would burn long and

bright enough to produce sufficient light. On October 21st 1879, Edison made a filament from carbonised

silk inside a bulb with no air in it...the bulb lasted over 40 hours. Modern bulbs contain a tungsten filament

surrounded by Argon gas which is inert and prevents oxidation of the filament. These bulbs are designed to

last over 3000 hours.

Thomas Edison and the light bulb:

150W

Edison’s first light bulb produced less light and

lasted for less time when compared to modern

filament light bulbs. Modern bulbs contain atungsten filament surrounded by Argon gas which is

inert and prevents oxidation of the filament. These

bulbs are designed to last over 3000 hours.

First light bulb

Thomas Edison inventor of the filament light bulb,

allowed homes for the first time to use clean, safe

and cheap electrical energy rather than ‘town gas’ or candles which were expensive, polluting and

relatively unsafe to use. A successful scientist, he

had over 1000 patents to his name.

Notes

Diagram

Thomas Edison Patent application Modern light bulb




py g

Electrical power and the light bulbElectrical power and the light bulb twotwo

Thomas Edison’s bulbs, although revolutionary were expensive and short lasting. Dr. Lewis Latimer , a

draftsman, engineer and inventor worked with Thomas Edison on the incandescent light bulb and invented

carbon filaments for the Maxim electric incandescent lamp, an invention for which he received a patent for in 1881. Edison’s light bulbs only lasted a few days, Latimer solved this problem by inventing a carbon

filament which didn’t burn out. Due to this discovery, light bulbs became cheap and reliable, lighting

homes, offices and even whole cities like London, New York and Montreal. He also wrote ‘Incandescent

Electric Lighting: A Practical Description’ which was published in 1890.

Lewis Latimer and the light bulb:

Latimer’s light bulb was longer lasting than

Edison's and less expensive to produce. His light bulbs relied on an inexpensive carbon filament to

convert electrical energy into light energy. These

bulbs lasted many times longer than Edison’s.

Patent application

Lewis Latimer further developed the light bulb for

widespread use in homes and offices during 1881whilst working for the Edison lighting company. He

supervised the conversion to electric light bulbs by

cities including New York, London and Montreal.

Notes

Diagram

Lewis Latimer His work Modern light bulb




Electricity supply and demandElectricity supply and demand oneone

Currently we use f_______ fuels like methane (CH4), oil and coal to supply the energy to

generate domestic electricity to meet World demands. Increasingly, new technological

developments have been developed to utilise renewable forms of e_______. This will prolongour reserves of fossil fuels and reduce polluting gases like carbon dioxide and sulphur dioxide.

Generated electricity is transported to the commercial, industrial, transport and domestic users

by a huge network of over ground and underground cables called the national grid.

Users of electricity:

Different users of electrical energy require different voltages and amounts of electricity. Domestic and

industrial users have the greatest demand for electricity. Transport users like the train operators require

electricity at over 10,000 volts. Domestic users (households) require electricity at mains voltage which is

230 volts. All users also require the majority of their electrical energy during the day. Very little is used

during the night. Explain why the amount of electricity you need alters over a 24 hr cycle ?

TransportCommercialDomestic Industrial

Word bank: fossil energy




Electricity supply and demandElectricity supply and demand twotwo

Although we continue to use fossil fuels to generate e__________ for residential, industrial,

commercial and transport users, the demand in Britain for electrical energy over the last 30 years has

not significantly increased. This may be because we have more efficient devices or that Britain nolonger manufactures large goods like cars. Demand for electricity follows a 24 hr cycle, where the

peak demand is usually around the early evening. The lowest demand for electricity occurs during the

middle of the night. During the winter we use more electricity due to the cooler temperatures and

reduced d___________ hours. Explain why when most winter heating is supplied using methane ?

Supply and demand: Word bank: electricity daylight

The two biggest user groups of electrical energy are domestic

(homes) and industry (factories) They consume just under 60%of the supply of electrical energy. Interestingly 8% of all

energy is wasted or lost from the system because of resistance

in overhead and underground cables of the national grid.

Demand for electricity follows a 24 hr cycle with peak

demands during the early evening when we all return home and begin cooking dinner. The lowest demand is during the night

when we are all asleep and not using appliances. Winter

demand is higher because of heating and lighting demands.

Demand for electricity in all user groupsDemand for electricity winter & summer (2001)




Generating electricityGenerating electricityThere are many p________ stations in Great Britain supplying millions of watts of electrical

energy to all our homes, every single day. A large power station produces enough electricity for

a city or about a million kilowatts every hour of the day. The majority of power stations inGreat Britain use fossil fuels like crude oil, c______ and natural gas. There are other types of

power stations that use alternative energy sources like nuclear power. There are also smaller

generating stations that use renewable energy sources, for example solar power or biogas.

Think of five types of renewable energy sources ?

Generating electricity:Word bank: power coal

BiogasRenewable

Notes

Diagram

Most power stations found in Great Britain and Europe combust coal, oil or natural gas. These fossil fuels

are cheap, abundant and contains vast amounts of trapped energy. Fossils fuels are ancient stores of energy,

the fossilised remains of dead organisms which died many millions of years ago. Once used, they cannot be replaced in our life times. This is why they are called non-renewable fuels. In the next century, fossil

fuels will have nearly run out and we will have to develop alternative technologies to generate the electrical

energy we consume.

Fossil fuels Nuclear


G ti l t i it i f il f lG ti l t i it i f il f l



Generating electricity using fossil fuelsGenerating electricity using fossil fuels

WasteGases

Furnace Coke or coal

Boiler

Steam

Turbine

Generator

Transformer 1

Transformer 2 Transformer 3 Customer

Overhead cables

Smoke stack

400,000V

33,000V

240V

Gas fired power station

WasteGases

Furnace Coke or coal

Boiler

Steam

Turbine

Generator

Transformer 1


Overhead cables

Smoke stack

400,000V

33,000V

240V

Gas fired power station

Energy trapped in fossils fuels like coal, oil and natural gas is released during their combustion

in power station boilers. This energy is used to produce s________, which drives huge turbine

generators. The movement of the copper coil across a magnetic field induces a current flow inthe copper wire. Electrical e_______ cannot be stored and is delivered instantly by the National

Grid to the consumer.

Generating and supplying electricity: Word bank: steam energy

Steam produced from combusting fossil fuels like oil and gas drives the turbine generators. A

current is induced in the cables. Electricity is transported at over 400,000 volts from transformer

one and two. At high voltages and low currents less energy is wasted during its transport. It is then

stepped down to around 33,000 volts where, before reaching your house, it is stepped down further

by transformer three to 230 volts. This is then ready for use by domestic appliances.

Notes

Diagram


F il f lF il f l greenhouse effectgreenhouse effect



Altitude (km)

15 50

S o l a r r a d

i a t i o

n

R a d i a t e

d o u t t o

s p a c e

Absorbed in atmosphereby greenhouse gases

Altitude (km)

S o l a r r a d

i a t i o

n

R a d i a t e

d o u t t o

s p a c e

Absorbed in atmosphereby greenhouse gases

15 50

Carbon dioxides traps heat

energy from the sun. The

amount of carbon dioxide in theatmosphere is increasing by 3

billion tonnes a year.

The greenhouse effect

The World’s energy demand and

the use of crude oil is

increasing. China in the nexttwo decades will use more than

the USA.

World’s crude oil use

There are over 500 million cars,

all pumping out carbon dioxide

from the combustion of octane or petrol. Car use is set to double

over 20 years.

Rising levels of carbon dioxide

Over the last century, our use of fossil fuels has released huge amounts of carbon dioxide into

our atmosphere. This has disrupted the b_________ between carbon in the form of carbon

dioxide and carbon found tied up under rock in crude oil, natural gas and coal. Currently we areadding an extra 3 billion tonnes of carbon each year into the atmosphere. The carbon dioxide

molecule traps infra red h_____ from the Sun. Slowly our planet is warming because of the

rising carbon dioxide levels. How can you reduce your dependence on fossil fuels like petrol

and natural gas ?

The greenhouse effect:

Fossil fuelsFossil fuels greenhouse effectgreenhouse effect

Word bank: balance heat


F il f lFossil fuels acid rainacid rain



Carbon dioxide is not the only pollutant that is released into the environment during

the combustion of fossil fuels. S_________ and nitrogen are also present in crude oil.

During combustion, both sulphur and nitrogen combine with oxygen to form sulphur dioxide and nitrogen oxides. These gases form weak a_______ when they react with

water in the atmosphere. Acid rain can damage forests and plant life. It can also

acidify lakes and ponds, disrupting natures balance.

Acid rain:

Fossil fuelsFossil fuels acid rainacid rain

The pH of rainfall is lowest where you find the highest

population across the East Coast. Almost 150 millionAmericans live, work, drive and pollute in this area. The

pH of rain water in some areas of the Eastern USA

seaboard has a very acidic pH of around 4.2.

pH of precipitation across America

Notes

Diagram

With 280 million Americans each using on

average a staggering 3kw per hour every dayof the year, the amount of Sulphur dioxide

gas emitted per year for every square

kilometre of land is around 0.4 of a tonne.

Polluting the Earth’s atmosphere

Word bank: sulphur acids

Generating electricity using nuclear powerGenerating electricity using nuclear power




Generating electricity using nuclear power Generating electricity using nuclear power Using fossil fuels to produce electricity adds to acid rain and global warming. They are also

running out, making it necessary to find alternative e________ sources. A nuclear power

station uses radioactive substances like uranium235

as a fuel. As uranium235

decays, largeamounts of energy is released which is then used to heat water producing steam which drives

turbine generators. Nuclear fuels are a highly concentrated energy source, with large nuclear

power stations only requiring about 10 kg of nuclear fuel per day. The only problem is that

radioactive w_______ materials need to be safely stored for many thousands of years.

Nuclear power supplying electricity:

Containment building

Fuel r ods

Steam

Turbine

Generator

Transformer 1


Overhead cables

400,000V

33,000V

240V

Nuclear power station

Containment building

Fuel r ods

Steam

Turbine

Generator

Transformer 1


Overhead cables

400,000V

33,000V

240V

Nuclear power station

Word bank: energy waste

Steam produced from the energy given out during the radioactive decay of Uranium235 drives the

turbine generators. A current is induced in the cables. Using nuclear fuels, although expensive does

not produce any polluting gases like carbon dioxide or sulphur dioxide. Safely storing radioactive

waste materials and high decommissioning costs still limit their use here in Britain.

Notes

Diagram


Inside a nuclear power stationInside a nuclear power station



Inside a nuclear power stationInside a nuclear power stationElectrical energy is produced using nuclear energy. Increasingly, nuclear energy is used as

an alternative to the combustion of fossil fuels like c______ oil and natural gas. This is

partly because they are a finite resource and currently contribute to global warming because of c___________ dioxide emissions. A nuclear reactor uses Uraniun235 as a fuel

source. These uranium rods glow white hot, in turn heating water, producing s_______,

which drives a turbine and generates e__________.

Nuclear energy: Word bank: crude carbon steam electricity

One problem is the

radioactive waste and its

safe storage. It has to bestored for up to 10,000

years safely away from

humans.

About 8% of our

electrical energy is

produced using nuclear fuels. In future years

this will rise as fossil

fuel use decreases.

Uranium235 rods glow

white hot and heat water

turning it into steam.This drive the turbines

generators producing

electricity.

A nuclear power station

with a characteristic

dome housing theradioactive core. They

are very expensive to

build and decommission.

Notes

Electricity Radioactive waste

Diagram

Power station Radioactive core


Risks of using nuclear energyRisks of using nuclear energy



Risks of using nuclear energyRisks of using nuclear energyGenerating electricity using nuclear energy raises a number of issues and enjoys limited

support in Britain. Furthermore, using isotopes like Uranium235 poses certain risks to us

all, in addition to dealing with the large amounts of radioactive waste produced as a by product. There are many reasons ‘ for and against ’ using nuclear energy and Uranium235.

The biggest argument for includes reducing our use of f_______ fuels and that only a

small percentage of background radiation comes from the nuclear power industry.

Nuclear energy: Word bank: fossil

Three-mile island in the

US was a nuclear power

station. A coolant failure

led to a ‘meltdown’ and

an explosion in thereactor. The radioactive

cloud affected a huge

area.

Receiving high doses

from gamma radiation

can lead to death and

radiation sickness. After

the initial death toll inJapan up to 500,000

people died within 10

years from cancer.

In Japan, during WWII,

America dropped two

‘Atom bombs’ on Japan.

The photograph shows

Nagasaki in completeruins just hours after the

atomic bomb was

dropped and detonated.

During testing of

nuclear weapons and

warheads, US soldiers

were asked to ‘witness’

the bomb close to thetesting site. Many have

since died prematurely

from various cancers.

Notes

Radiation sickness Three-mile island

Diagram

Nuclear weaponry Nagasaki

Renewable energy sourcesRenewable energy sourcesScience Interactive LTD Copyright 2005



Renewable energy sourcesRenewable energy sourcesRenewable alternatives to using crude oil for generating electricity are now being

developed. These new technologies will reduce our dependence on crude oil, as well as

reducing carbon dioxide e__________. Many sources of energy that we currently useevery day are now renewable. This means that unlike coal, natural gas and crude oil, they

are not used up. Scientists will continue to work towards almost zero reliance on fossil

fuels for the future production of electricity.

Overview of renewable energy:Word bank: emissions

Using moving water, hydro-

electric dams are able to

generate clean electricity.The only problem is that you

need lots of space and lots of

rain every year.

Converting animal waste like

manure from farming into

methane, using bacteria is away of replacing fossil fuels

like natural gas. What is the

formula of methane?

Solar cells using solar

energy could power traffic

lights and street lamps.They are only useful in

countries with high rates

of sunshine.

Wind farms could supply

up to 20% of the energy

we use every year. Whydo people in the

countryside object to

these wind farms ?

BiogasWind Solar Hydroelectric


Generating electricity using biogasGenerating electricity using biogas



Fermentor

Turbine

Generator

Transformer 1 Customer

33,000V 240V

Manure Fermentor

Steam

Waste

Gases

Furnace

Boiler

Transformer 2

Biogas

Electricity can be generated on a small scale using biogas. Biogas is exactly the same as natural

gas, the fossil fuel extracted from underneath the north sea, but it is produced by b_________

respiring animal wastes like manure. This is therefore a renewable supply of gas which can beused in the same way as fossil fuels, with the heat energy used to produce steam, which in turn

drives a turbine generator. Why is the amount of electricity generated using this method very

small at present ?

Biogas supplying electricity:

Fermentor

Turbine

Generator


33,000V 240V

Manure Fermentor

Steam

WasteGases

Furnace

Boiler

Transformer 2

Biogas mini power station

Fermentor

Turbine

Generator


33,000V 240V

Manure Fermentor

Steam

WasteGases

Furnace

Boiler

Transformer 2

Biogas mini power station

Word bank: bacteria

Steam produced from the heat energy given out when natural gas (CH 4) is combusted with oxygen

drives the turbine generator. A current is induced in the cables. Electricity is transported to

commercial and domestic users only. Using biogas, although expensive and still contributing to

greenhouse gases does recycles animal waste like manure.

Notes

Diagram

Generating electricity using biogasGenerating electricity using biogas

Generating electricity using solar powerGenerating electricity using solar powerScience Interactive LTD Copyright 2005



Generating electricity using solar power Generating electricity using solar power Solar power can be used directly to generate small amounts of electricity using photovoltic

cells. These produce a low c________ and are only useful for producing electricity in remote

areas or for devices that only require a low current, for example calculators. Using solar power to heat water creating steam which then drives a turbine generator is another way the Sun’s

energy can be used to generate electricity. E_________ regions that receive plenty of sunshine

are ideal. The only problem is that the technology is still relatively expensive. Why is the UK

not an ideal location for solar panels or cells ?

Solar power supplying electricity: Word bank: current equatorial

Steam produced from the heat energy collected by solar reflectors drives the turbine and generator.

A current is induced in the cables. Electricity is transported to commercial and domestic users.

Using solar cells is expensive and is only viable in countries with good weather. Solar cells can be

used to directly generate electricity. These are very useful where there is demand for energy in very

remote areas like the desert or away from major towns and cities.

Notes

Diagram

Generating electricity using geothermal powerGenerating electricity using geothermal powerScience Interactive LTD Copyright 2005



Generating electricity using geothermal power Generating electricity using geothermal power Where the Earth’s crust is thin or where it contains large amounts of radioactive

substances like Uranium235 a ready heat source from ‘hot rocks’ is available. Water can be

superheated producing s_______. Geothermal power stations makes use of this energy byheating water and producing steam which then drives turbine generators. This is a

c_______, renewable energy source. If there is insufficient energy to produce steam, the

heated water is used in people’s homes. Why is this technology not used in England, but is

found in Iceland ?Geothermal power supplying electricity: Word bank: steam clean

Steam produced from the heat energy collected by water that is pumped deep into to the Earth’s

crust drives the turbine generator. A current is induced in the cables. Electricity is transported to

commercial and domestic uses only. These geothermal power stations are only found where theEarth’s crust is thin enough to allow the heating of water. Many cities in Iceland generate their

electricity using geothermal energy.

Notes

Diagram

Generating electricity using gravitational potential energyGenerating electricity using gravitational potential energyScience Interactive LTD Copyright 2005



Generating electricity using gravitational potential energyGenerating electricity using gravitational potential energyWater held behind a dam, stores huge amount of gravitational potential energy. When the

stored water is allowed to flow downhill, its kinetic energy is used to drive turbine generators,

which in turn produces electricity. Hydroelectric dams are usually constructed in mountainousareas with high yearly rainfall levels. The three gorges dam is the largest r__________ and is

currently under construction in China. When finished, it will generate millions of kilowatts of

electricity. Although this is renewable e_______ up to ten million people will be displaced

when the valley is flooded. Why is this technology used only in wet mountainous areas ?

Moving water supplying electricity: Word bank: reservoir energy

Large amounts of land and rainfall are required for any hydroelectric dam. The main

advantages of hydroelectricity is that it is a renewable form of energy and the start up time

from allowing the water drop to generating electricity is less than a second. Electrical energy

generated in this way is used to supply electrical power during peak demands.

Notes

Diagram


Understanding kilowattsUnderstanding kilowatts oneone



The power rating of an appliance tells us the number of joules that it uses every second

and the overall power of the appliance. If you were choosing between a 300 watt and 500

watt drill, you might choose the 500 watt drill if you had to drill through concrete. This is because the ‘strength’ of the drill will be higher, therefore the 500 watt drill will be more

able to drill very hard concrete. Below are some examples of the power ratings and the

energy (Js-1) that these d________ use, every second. Try looking for the power rating of

your computer and play station at home ? (found underneath or rear of the product)

Energy and the joule:

Understanding kilowattsUnderstanding kilowatts

Word bank: devices

A hearing aid, one of the

smallest electrical devices

running off small watch batteries uses only 0.0001

joules per second.

Hearing aid

A hair dryer has a

power rating of 900

watts and uses 900 joules of electrical

energy per second.

Hair dryer

Notes

Diagram

A city that has a

population of about ten

million people usesabout 30,000 million

joules per second.

City

A new born baby

weighing just 6 kg and

taking their fist stepsuses about 25 joules per

second.

Baby


Understanding kilowattsUnderstanding kilowatts twotwo



Understanding kilowattsUnderstanding kilowatts

2.5

2.0

1.5

1.0

0.5

0.0Light bulb (100 W)

Laptop (180 W)

Toaster (900 W)

Drill (1200 W)

Hair dryer (1500 W)

Kettle (2000 W)

Heater (2500 W) 2,500

2,000

1,500

1,000

500

0

W a t t s K

i l o w a t t s

A kilowatt hour is equal to the energy consumed by a 1,000 watt device that is switched for one

hour . The amount of e__________ a power plant generates or a customer uses over a period of

time is measured in kilowatt hours (kWh) Kilowatt hours are determined by multiplying thenumber of kW's a device uses by the number of hours the device remains switched on. For

example, if you use a 100 watt light bulb for 10 hours, you have used 1000 watts of power, or

1 kWh of electrical energy. The table below shows typical values for power usage of some

household appliances. Remember Power (Watts) = Voltage (V) x Current (I)Power ratings: Word bank: electricity

Cost of electricityCost of electricityScience Interactive LTD Copyright 2005



Cost of electricityCost of electricityThe cost of using electrical a___________ at home is calculated using the Kilowatt

hour. The electricity m_______ records how many kWh units of energy your house

uses per year.

Calculating the Kilowatt hour

Working out the cost of electricity:

Energy transferred (kWh) = Power (kW) x time (h) x cost of 1 kWh (£)

Word bank: appliances meter

____________ __________ ?

_____________ ___________ ?

3 kW x 6 h x 5p= ________

0.1 kW x 5.0 h x 5p= 2.5 pence

Total cost

6 mins30 mins6 h5.0 hTime used

Diagram(N.B. Cost of 1

kWh = 5p)

3 kW Washer 5 kW Cooker 500 W Dyson2 kW Toaster Appliance


The cost of electricity in your homeThe cost of electricity in your home



The cost of electricity in your homey yWe all have to pay for the electricity that we consume in our homes. In every home, you will

find an electricity meter . This records the amount of electrical e_______ your home uses. The

electricity company records the number of units (kilowatt hours) that you use every quarter bycomparing the previous reading with the current reading. Once the meter has been read, the

electricity company sends you a b_____ showing how many units you used, their cost and a

payment date. How can you help your parents reduce the amount they pay for their electricity ?

The cost of electricity:An example of an electricity bill

Notes

Diagram

A typical bill is sent every three months toyour home by electricity companies.

1: Account number

2: Bill date

3: Customer address

4: Number of units used5. Price per kilowatt hour

6: Total amount due including all charges

Electricity meter

Word bank: energy bill

Electricity and its dangersElectricity and its dangersScience Interactive LTD Copyright 2005



y gy gMains electricity, overhead cables and substations are all dangerous. The electricity that

we use in our homes has a voltage of 230 volts. At this voltage, the current carried in the

live wire has sufficient energy to kill you. Although there are many inbuilt s_______ measures, working with or using e__________ is dangerous, even when changing a plug

at home. If you are unsure of how to work safely with electricity or don’t know the basic

safety rules, you may cause the death of yourself or worse still: others.

Dangers of using electricity: Word bank: safety electricity

Illustrated by these pictures are some of the dangers of using or working with electricity. Picture 1:

An electrical fire caused by a short in a sub-station. Picture 2: Wherever you seen this sign ‘keep

out’ remember overhead cables and substations carry electricity at huge voltages. Picture 3: This person is highly trained and observes very stringent safety rules. Electricity will always flow to

Earth, even through you if you give it the opportunity. Remember electricity can kill !

Notes

Warning

Diagram

Electrical fires Electrocution


Domestic electricityDomestic electricity



Domestic electricityo est c e ect c tyA modern household circuit supplies electricity at 230 volts to lights, sockets and all appliances.

The live wire ( brown) carries the current with the highest voltage from the power station

through the main fuse box, meter and main residue c________ circuit breaker. Each socket and plug is also protected by its own fuse. Current, at a lower voltage returns to the power station

through the neutral wire ( blue). If l______ current should escape due to a fault in the appliance,

it is taken safely away through the Earth wire which is green and yellow in colour.

Mains circuit in the home:

meter

65999

kWh

L N E

F u s e 5

A

Fuse 13A

M

a i n s w i t c h

Socket ring main

Lights ring main

meter

65999

kWh

L N E

F u s e 5

A

Fuse 13A

M

a i n s w i t c h

Socket ring main

Lights ring main

Word bank: current live

There are two ‘ring main’

circuits.

Circuit 1: Supplies electricity

at 230 volts and 5 amps for

lights.

Circuit 2: Supplies electricity

at 230 volts and 13 amps for

the sockets.

Find where the electricitymeter is placed. What unit of

power does it measure ?

Notes


Safety features of domestic wiringSafety features of domestic wiring



y gy gElectricity is dangerous and using it at home requires some safety precautions. The l______

wire is the most dangerous...carrying mains voltage at 230 volts. This will easily kill you. The

n________ wire carries the current back to the power station, usually at a low voltage which isclose to zero. The e________ wire is for safety and only carries a current if there is a fault in the

appliance. There are many safety features that ensure that using electricity at home is as safe as

possible. Why is it also our responsibility to make sure we know the dangers of using electricity

when at home ?Safety at home:

L i v

ewi r e N

e u t r a l

Current surge breaks circuit

Electromagnet

In appliances, if the live wire

becomes loose, then the Earth

wire returns the stray current

back to Earth. Without an Earth

wire, the current might travel

through you and kill you.

A surge in current causes an

electromagnetic effect in the

RCCB. This causes the contact

point to pull apart therefore

breaking the current supply to

the house.

Main fuses will melt if there is

a current surge through the

live wire breaking the supply

to your house. Fuses fitted in

plugs and fuse boxes need to

be the correct rating.

Notes

Diagram

Earthing electricityRCCBMain fuse boxPart

Word bank: live neutral earth


The electrical plugThe electrical plug oneone



All appliances require a plug so that electricity can flow through the device supplying it

with electrical energy. Most appliances are now sold with a p_____ already fitted. A plug

has several features that makes it very safe to use: It has a tough plastic case, a cable gripto prevent the f______ from coming away from the plug and pins that a partially insulated.

A plug is also supplied with a fuse that breaks the circuit if there is a current surge. Try

wiring a plug safely. Make sure the live, earth and neutral are connected to the right pin ?

The plug one

The cable from the

plug to the appliance

should never be

broken. If it is then itneeds to be replaced

with new cable.

Electrical flex

There are three pins connected to

three wires: Live ( brown) takes

the current from the power

station, neutral ( blue) returns itand Earth (green & yellow) takes

stray current to ground.

Wiring a plug

Notes

Diagram

Features of a plug include its

tough outer case, insulated pins

and cable grips. You should

always replace a broken plugand make sure you do not

overload sockets.

Household plugs

Word bank: plug flex


The electrical plugThe electrical plug twotwo



Stops wires from

being pulled out.Grip

Takes supply at 230V

to your appliances.Live

Returns current to

p_________ station.

Neutral

Melts and b_______

the circuit.Fuse

Returns stray current

to e________.Earth

All plugs have to be fitted with the correct fuse. The fuse is required to protect the device

from potentially dangerous c________ surges. A current surge can damage your appliance

by melting circuits or if the current is large enough, it may even cause an electrical fire.When a current surges, the f______ wire will get hot and eventually melt, therefore

breaking the circuit. This stops a dangerous surge in current reaching your appliance. Why

do they make fuses with metals with relatively low melting points ?

The plug twoWord bank: current fuse earth breaks power

Fuses are made from metals

with low melting points.

When a current surges, the

fuse becomes hot. If thissurge is large enough it will

melt and break the circuit.

Melting fuseParts of a plug

Notes

Diagram

Wiring a plug: Practise

wiring a plug. You need to

connect the right wire to the

right terminal and makesure there are no loose

connections.

Household plugs

Understanding FusesUnderstanding Fuses




The fuse rating in amps depends on the appliance and the current it requires. The fuse rating is the

maximum current the fuse can carry without m___________. Only certain values are available: 3 A,

5 A, 13 A & 30 A.

Example: A drill has a power rating of 690 W and uses 230 V mains. What fuse should be fitted to

the drills plug ? Current = 690 W/230 V = 3 A. A 5 amp fuse should be fitted. A 3 amp would melt

and a 13 amp fuse might allow a damaging current to flow before melting.

Working out the correct fuse rating:

Equation: Current (Amps) = Power (W) / Voltage (V)

Word bank: melting

______________ ______________

_____________ ?

_______________ _______________

______________ ?

______________ ______________

_____________ ?

5750 W/230 V= 25 Amps

= 30 Amp fuse

Correctfuse

2000 W

230 V

115 W

230 V

2300 W

230 V

5750 W

230 V

Power (W)

Mains (V)

Diagram

KettlePlay stationWashing machineCooker Appliance


Understanding electromagnetismUnderstanding electromagnetism



If you place a magnetic compass near to a copper wire that is carrying a current, the compass’s

needle will be attracted away from ‘true north’ towards the wire. This is because a flow of

e__________ through a conductor has a slight magnetic effect. A temporary electromagnet can be created when a current flows through a wire which surrounds an iron core. The current

induces a magnetic effect in the iron core, as long as c__________ flows. Electromagnets are

used everywhere and are found in scrap yards, buzzers and electrical motors. Name three other

uses of electromagnets ?

Electromagnetism:

A wire carrying a current coiled around an iron core induces a

temporary electromagnetic. Electromagnets are used in a wide

range of applications. As soon as the power is switched off, themagnetic effect stops. You can also control the strength of an

electromagnet.

Even a small current in a wire

has an effect on a magnetic

compass. When reading acompass, you should never use

near electrical appliances.

Notes

Diagram

The electromagnetic effect and electromagnetismElectromagnetic effect

Word bank: electrons current


Uses of electromagnetismUses of electromagnetism



Electromagnets are used everywhere. They have several advantages over permanent magnets

because they can be switched on or off and they can be made many more times powerful than

permanent m_________. Iron is a valuable material and can be recycled and sorted from other materials using a ‘lifting electromagnet .’ A MRI (magnetic resonance image) is used to image

body tissues. This produces an image far clearer than ultrasound or X rays. Also, airport

security uses electromagnets to detect the presence of m______ on a passenger. When you pass

through, metals will sound the alarm. Why are metals considered a risk to airplane travel ?

Uses of electromagnetism: Word bank: magnets metals

An electromagnet is used to

increase air security when

flying. A metal object, for example, a gun or bullets will

trigger an alarm.

A powerful electromagnetic

is used to image the inside of

the human body. This deviceis called a magnetic

resonance imager or MRI.

A temporary electromagnet

is used to sort scrap iron and

steel from other scrap metalslike aluminium, zinc, copper

and magnesium.

Notes

Diagram

Airport securityMRI Scanner Recycling iron


Defining electricityDefining electricity



We see lightning, the effects of electrostatic charges or s______ electricity all the

time. We also see electrical energy being used by many devices, but where does it

come from ? The answer is inside the a______ of conducting materials like copper.Electricity is a flow of e_________ through a conducting material. A conducting

material consist of millions of atoms, where electrons are free to leave their o______

and flow in an electrical current.

Inside the atom:

Nucleus _______ ?Proton

In Orbits _______ ?Electron

Nucleus _______ ? Neutron

PositionChargeSub-Atomic

particle

The atom is made from protons, neutrons and

electrons which orbit the positive nucleus.

Electrons in metals are free to leave the atom

and flow in an current when a voltage is applied.

Some metals like copper and gold are goodconductors meaning they allow electrons to flow

easily from atom to atom.

-

--

-

-

-

-

-

- -

Diagram

Sub atomic particlesInside the atom

Word bank: static atom electrons orbit


FaradayFaraday his work his work

h l d b i k f hi k i h l i i d i i



Michael Faraday born 1791 is known for his work with electricity and magnetism. Despite

having little or no formal educational, Faraday went on to discover electromagnetic induction,

electropotentials in b_________, the electrical plasma arc and the Faraday cage. He publishedhis work in several volumes detailing all his discoveries. He also instituted the ‘Christmas

lectures’ which brought science to children. Imagine your life without electrical energy or

batteries ! Write a short description of how things would be different ?

Faraday and his work:

One of Faraday’s many

inventions included the

plasma arc. He demon-

strated this principle in

the 1830s.

The plasma arc

Notes

Diagram

Michel Faraday born

22nd September 1791

died August 25th 1867.

Pioneer in electricity

and magnetism.

Faraday

Faraday went on to discover electromagnetic

induction, electropotentials in batteries, the

electrical plasma arc and the Faraday cage. He

published his work in several volumes detailing all

his discoveries.

Faraday’s published work

Word bank: batteries


FaradayFaraday inducing a current inducing a current

Mi h l F d ’ di i 1831 h i i fi ld d d



Michael Faraday’s greatest discovery in 1831 was that a moving magnetic field produced an

electric current or flow of e__________ inside a conducting wire. Faraday, building on the

work of Charles Coulomb and Andre Ampere had demonstrated that when a wire crosses amagnetic field , a current is induced. The principle of electromagnetic induction was a landmark

in science, for it made possible the d_________ or generator which is able to produce cheap,

clean, transportable and relatively safe electrical energy. Find out what Coulomb and Ampere

discovered ?

Faraday and his work:

Motion

Current flow

Magnet

S o u t h

N or t h

Turbine generators

Notes

Diagram

Michel Faraday born

22ns September 1791

died August 25th 1867.

Pioneer in electricity

and magnetism from

1831 to 1855.

Faraday

Dynamos and turbine generators found in power stations both generate

electricity. They both have a coil of wire which spins at high speeds in a

magnetic field. When the wire coil crosses the magnetic field, a voltage is

induced across the wire. There are three ways to increase the size of voltage

induced in the copper coil: 1: Use a stronger magnet 2: Use a coil with more1: Use a stronger magnet 2: Use a coil with more

turns 3:Spin the coil faster.turns 3:Spin the coil faster.

Electromagnetic induction

Word bank: electrons dynamo


In a coal fired power station the steam produced when combusting fossil fuels like coal drives huge

Generating a current for domestic useGenerating a current for domestic use



In a coal fired power station, the steam produced when combusting fossil fuels like coal drives huge

turbine generators. These work a bit like an electric m_______ in reverse. Movement of the copper

coil across a magnetic field induces a c________ and voltage. The current enters and leaves the

generator through brushes, which are connected to ‘O’ rings. As the generator rotates (50 times asecond), the current moves back and forth. This is why it is called alternating current. Remember, it

is the movement of the copper coil across the magnetic field that gives sufficient energy to the

electrons to flow in a current .

Inducing an electric current:

S t e a m

t u r b i n

e g e n e r

a t o r

Word bank: motor current

Turbine generators

Notes

Diagram

Steam drives the turbine generators which produces an electric current. As the coil of copper wire

moves through the magnetic field, energy is transferred to the electrons. These generators are around

60% efficient and can generate up to 500,000 kilowatts per hour. Steam can be produced by either combusting fossil fuels like coal, gas and oil or by using nuclear energy. Why are power stations

situated near supplies of water and fossil fuels ?

Power station and turbine generators

Generating alternating currentGenerating alternating current oneone

The current produced by a turbine generator found in all power stations flows




The current produced by a turbine generator found in all power stations flows

momentarily in one direction and then, it r_________ and flows in the opposite direction.

This cycle is repeated continuously. The frequency of this change in direction is 50 times a

second or 50 H z . This is called ‘alternating current,’ generally shortened to AC. Mains

current is supplied as a___________ current, reversing its direction 50 times a second.

This type of current is fine for simple devices like light bulbs and toasters, but direct

current which flows in one direction only is required for complex machines like

televisions and computers.

Alternating current: Word bank: reverses alternating

iode laced in circuit

Time (S)

+23 0

0

-230

V o l t a g e

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

iode laced in circuit

Time (S)

+23 0

0

-230

V o l t a g e

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

Simple devices like toasters,

lights, kettles and heaters canuse normal mains alternating

current.

Using AC current

Notes

Diagram

The trace shows mains alternating current which changes

direction 50 times a second. This frequency gives some ideaof the speed the coil must turn inside the generator. Unit of

frequency is the Hertz (i.e. 50 Hz = 50 cycles per second)

Mains alternating current

Generating alternating currentGenerating alternating current twotwo

Dynamos and turbine generators found in power stations both generate electricity. They both




Dynamos and turbine generators found in power stations both generate electricity. They both

have a c______ of wire which spins at high speeds around a magnet. When the wire coil

crosses the magnetic field , a v________ is induce inside the wire. There are three ways to

increase the size of voltage induced in the copper coil:

Alternating current:

1: Use a stronger magnet 2:Use a coil with more tu1: Use a stronger magnet 2:Use a coil with more turns 3:Spin the coil faster rns 3:Spin the coil faster

Word bank: coil voltage

V o l t a

g e

+230V

-230V

Time 0.1Time 0.1 0.20.2 V o l t a

g e

+230V

-230V

Time 0.1Time 0.1 0.20.2

Driver

Axel

Copper coil

Iron core

Magnet

Contact

Output

Inside a bike dynamo

Notes

Diagram

The trace shows mains alternating current which

changes direction 50 times a second (50 Hz.) Notice

how the direction of the current follows the position of the armature that is found inside the turbine generator.

Mains alternating current

Direct currentDirect currentA current that continuously flows in one direction is called a ‘direct current ’ or




A current that continuously flows in one direction is called a direct current, or

abbreviated to DC. An example of direct current is the current supplied by a

b________ or cell. Direct current is used for electric trains, other motor drivendevices and complex devices like computers. These devices could not use alternating

current because of the change of polarity every 50th of a second. This means that a

motor would change direction 50 times per s_______ and effectively not turn in any

one direction.

Direct current: Word bank: battery second

Time (S)

+ 23 0

- 230

V o l t a g e

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

Time (S)

+ 23 0

- 230

V o l t a g e

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

Complex equipment requires

current that travels in onedirection only. AC current is

converted to DC current.

Using DC current

Notes

Diagram

A direct current is supplied by a battery. It only flows in

one direction. Alternating current can also be converted todirect current using a diode. Complex devices like

computers and motors require direct current.

Direct current in circuits


Fleming’s right hand ruleFleming’s right hand rule oneone

To determine the direction of a current flow in a circuit or single wire when it cuts across



To determine the direction of a current flow in a circuit or single wire when it cuts across

magnetic lines of flux (north to south), we use Fleming’s right hand rule. This simple rule

is easily used so that we can work out the d__________ of the current flow through asimple wire. Remember that understanding this rule, allows us to understand how we

generate electricity for commercial, residential and industrial users.

Fleming’s right hand rule:

Then your seCond finger indicates thedirection of the Current flow in the wire.

SeCondfinger

Rotate your hand about that finger until your

thuMb points to the direction of the Movement

of the wire.

ThuMb

Point your First finger in the direction of the

Magnetic Field (from north to south)First finger

RuleHand digitMovement of the wire

Magnetic field

Direction of currentSecond finger

First finger

ThumbMovement of the wire

Magnetic field

Direction of currentSecond finger

First finger

Thumb

Using Fleming’s right hand rule is simple and tells us the direction of a current in a

wire. This is determined by the direction of the movement of the wire across the

magnetic lines of flux. Practise this rule with your right hand and after a few

attempts it becomes very simple.

Notes

Rules

Diagram

Flemings right hand rule

Word bank: direction


Fleming’s right hand ruleFleming’s right hand rule twotwo

Work out the direction of current in the four examples below Use Fleming's right hand



Work out the direction of current in the four examples below. Use Fleming s right hand

rule to determine the direction of a current flow in a circuit or single wire when it cuts

across magnetic lines of flux (north to south.) Remember that understanding this ruleallows to understand how we generate electricity for commercial, residential and industrial

use.

Fleming’s right hand rule:

S

N

S

N

N

S

S

N

No movement

S

N

S

N

S

N

S

N

N

S

N

S

S

N

S

N

No movement

Work out which way the current flows in the wire ? (out of the page or into the

page) Start with the direction of magnetic lines of flux and then the movement of

the wire and work out the direction of the current in the wire. Practise until it

becomes second nature.

Diagram

Problem four Problem threeProblem twoProblem one


Transforming electricityTransforming electricityTransformers can be used to step up or step down voltage Most transformers at home



Step up or step down transformersInside a transformer

10,000 V to

230 V.

230V to5 V.

If the secondary coil has

fewer turns than the primary

coil then it is a step down

transformer, because the

secondary voltage is smaller

Step

down

230 V to

10,000 V.If the secondary coil has

more turns than the primary

coil then it is a step up

transformer, because the

secondary voltage is larger.

Step

up

Examples NotesType

Transformers can be used to step up or step down voltage. Most transformers at home

are used to provide a low voltage p_______ supply from high voltage domestic mains

electricity for devices like computers, radios and televisions. These devices requirelow voltages because of their delicate components and circuit boards. A transformer

uses alternating current in one coil to induce alternating current in another coil with a

different and l_________ voltage. When do we use step up transformers ?

Transformers and voltage: Word bank: power lower


Working with transformersWorking with transformersA transformer contains two coils of wire wound on an iron core These wires are



A transformer contains two coils of wire, wound on an iron core. These wires are

linked by the iron core. We can work out the output or input voltage or even the

number of turns for the primary or secondary coil by using the following formula.

Solving problems with transformers:

Secondary voltage Number of turns on secondary coil V2 = N2

Primary voltage Number of turns on primary coil V1 = N1

=Secondary voltage Number of turns on secondary coil V2 = N2

Primary voltage Number of turns on primary coil V1 = N1

=

???Step down/Step down

5 V??Output voltage (V2)

10 V20 V10 VInput voltage (V1)

5050 turns400 turnsSecondary turns ( N2)

?100 turns100 turnsPrimary turns ( N1)

Example threeExample two

Diagram

Example one

Power distribution and the national gridPower distribution and the national gridPower stations are usually found away from large cities. The electrical energy they produce needs to




be transported over large areas. A network (national grid ) of cables, pylons, substations and

transformers supply all the cities in England with electricity. Electrical energy is transported from the

producer to the user at very high v__________ and low c__________. This reduces resistance andthe ‘heating effect ’ therefore saving energy, fossil fuels and money.

Transformers and the national grid:Word bank: voltage current

Notes: AC electricity is generated by high speed turbines driven by steam produced from combusting fossil fuels like

coal. Before transport across the UK, electricity is stepped up to 400,000 V or higher to minimise the current andresistance. Closer to large cities and industrial areas, the voltage is stepped down to 132,000 V. Heavy industry like car

factories use electricity at 33,000 V. Light industry uses electricity at 11,000 V. In towns, local substations transform the

electricity to 230 V for domestic use. The customer is billed in kilowatt hours by electricity companies.

All users of electricitySubstation/transformers National grid network Power station


Extension questions and homework

1: Define the following terms: Electricity, Alternating current, Direct current, Turbine, Generator, Power-station,



g y, g , , , , ,

Transformer & National Grid.

2: Look at the three pictures below. Complete the table.

3: Answer the following:

a) The strength of a induced current depends on three factors. Name them and explain how each one affects thestrength of the current.

b) Use your knowledge of circuits to design an alarm against intruders using a 3 volt cell, a buzzer, a trip switch

and conducting wires.

c) How is the heating affect used in appliances like heaters and kettles.

d) Explain how fossil fuels like coal and natural gas are use to generate electricity.

e) Explain why it is important to use renewable alternative to fossil fuels to generate electricity.

Power station

Power cables

Electricity Meter

Role in electricity productionPicture


4: Look at the four pictures below. Complete the table:



5: Answer the following:a) Explain with a simple diagram the difference of the atoms in a conductor and an insulator.

b) Explain with a simple diagram how you would induce a current using a magnet, a copper wire and motion.

c) What devices would you use to measure the voltage and current in a circuit. Draw a circuit diagram using the

correct symbols.d) Draw the following circuits: (i) Parallel circuit with 3 bulbs, two cells (1.5 V) and 3 switches controlling all 3

bulbs independently. (ii) Series circuit with 2 bulbs, one cell (9 V) and one switch.

e) What devices in the home uses the heating effect. List 3 and draw one of them.

f) What devices in the home use electrical energy to produce kinetic energy, sound energy and light energy. List

three and draw one of them.

g) Why do all houses use parallel circuits for its sockets and lights.

Joules per second

3000 wattsToaster

What is the electrical energy converted to ?

2000 wattsHair Dryer

3000 wattsKettle

60 wattsBulb

Power ratingPicture


6: Complete the following table:

Correct fuse (3A, 5A, 10A & 13A)Current (I)Voltage (V)Power (W)Appliance



9230Tumble dryer

4230Hairdryer

230230TV

3 A1224Light bulb

( )( )g ( )( )pp


a) A vacuum cleaner is labelled 230 V & 460 W. When connected to the 230 V mains supply, what current does it

take.

b) When operating from the 230 V mains supply, the current in a heating element of an electric fire is 4.5 A.

Calculate the power of the heater in watts. How many joules per second of energy is transferred through the

device.c) The three conducting wires that form the electricity cable to a house are called.

d) Which wire in a standard plug carries the current back to the power station.

e) Which wire in a standard plug carries the current at the highest voltage. Explain your answer.

f) How does the fuse protect the appliance and why is having the correct fuse for the appliance important.

g) Explain the differences between a modern circuit breaker and a metal fuse. Detail how they work differently and

state which one gives you the user the most protection and why.

h) Explain why an appliance with a plastic case requires no earth cable but an appliance with a metal case requires

an earth cable. Why are appliances with plastic cases said to be double insulated.

i) Suggest why it is illegal to have a main socket fitted in the bathroom.

j) Explain why manufactures of lawnmowers and other outdoor power tools recommend that they should be used

with a residue current circuit breaker.k) Why should you never climb an electricity pylon or break into a substation.

l) Why should you always replace a plug that is broken.



a) What type of current will a transformer work with.

b) Explain why electricity is transported at high voltage and low current around the national grid.



c) Explain with the aid of a diagram how a cycle dynamo generates electricity for the front and rear lights.

9: Complete the following table:

1000240 V11,000 V

12,00011,000 V132,000 V20012 V240 V

10100200 V

10010100 V

Step downStep upSecondary turnsPrimary turnsSecondary voltage (AC)Primary voltage (AC)


A 24 V lamp needing 2 A is supplied from a transformer connected to 240 V mains.

a) What is the turns ratio of the primary to secondary coil.

b) How much power is supplied to the lamp [power (watts) = voltage x current]

c) How much current is taken from the mains.

d) How long in time, would 1 kW power the lamp for.

e) 460,000 watts (W) of power may be supplied through the national grid at (i) 230 V or (ii) 230,000 V. Calculate

the size of the current for each voltage.(f) Why is 230,000 V used despite the dangers of high voltage electrocution.

(g) What are the energy changes in the process which begins with natural gas arriving at the power station and ends

up in a light being switched on in your home.

h) What are the advantages and disadvantages of overhead and underground cable. Make a table and compare the

two methods of transporting electricity.

Internet:Go to google.co.uk and find out about generating electricity. Make a short summary, include diagrams and name

the website that you used.

electricity uses etc

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