gcse electricity to the home

8/11/2019 GCSE Electricity to the Home

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Electricity and movement

What is the connection between electricity and movement?


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Energy transfer in the home

Electricity in the home is an

essential source of energy for

many appliances.

In all electrical appliances,

electrical energy is transferred to

other types of energy, forexample:

a fanconverts electrical energy into kinetic energy

a speakerconverts electrical energy into sound energy

a kettleconverts electrical energy into heat energy

How is electrical energy created in the first place?


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How is electrical energy produced?

Most methods of producing electricity involve converting

movement (i.e. kinetic energy) into electrical energy.

How does this key energy transfer take place?

Coal, oil, gas and nuclear

power stations convert kinetic

energy from high-pressure

steam into electrical energy.

Wind turbines convert kinetic

energy from wind into

electrical energy.


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Electricity is created from

the movement of a wire in a

magnetic field, or the

movement of a magnetic

field within a coil of wire.

Creating electricity from movement

In power stations and wind turbines, induction takes place in

generators. Here, a large turbine spins a magnet around

within a set of coils, inducing a large electrical current.

This is called

electromagneticinduction. It was discovered

by Michael Faraday, a British

chemist and physicist, in 1831.


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Electromagnetic induction


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Factors affecting induction

Electricity is induced when a

magnet moves inside a coil

of wire. When the magnet

stops moving, so does the

electrical current.

What factors affect the size of the electrical current induced?

The speedof the magnetthe faster it moves, the

larger the current.

The strengthof the magnetthe stronger the magnet,the larger the current.

The number of turnsin the coilthe more turns in the

coil, the larger the current.


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How can motion produce a current?



Electrical power is the rate at which an electrical appliance

uses electrical energy. All appliances have a power rating.

What is electrical power?

Power is measured in watts(W). 1000 watts = 1 kilowatt

(kW).1 watt of power means that 1 joule of energy is used

every second.

Appliances that need to create heat,

such as washing machines, cookers,

hair dryers and kettles, usually use

the most power.

TVs, radios and computers usually

use the least amount of power.



Power is measured in watts(W) or kilowatts(kW).

Current is measured in amps(A).

Voltage is measured in volts(V).

What are the units of power, current and voltage?

What is the formula for electrical power?

power = current x voltage

P =Ix V

In electrical devices, power can be calculated using the

formula:



A formula triangle helps you to rearrange a formula.

The formula triangle for P = IVis shown below.

Cover up whatever quantity you are trying to find to leave

the calculation required.

So to find current (I),cover up I which givesthe formula

I =P

V

Can I use a formula triangle?

x



A filament bulb has a potential

difference of 200V across it and a

current of 0.2A running through it.

How is power calculated?

At what power is the filament bulb

operating?

= 40W= 0.2

A x 200

V

P = IV



Electrical power calculations



Power is measured in kilowatts (kW) and the time ismeasured in hours (h), so what are the units of electricity

measured in?

1 unit of electricity = 1 unit of electrical energy

Example:

How many units of electricity is 17.6 kWh? 17.6 units

The amount of electrical energy (i.e. the amount of electricity)

used by an appliance depends on its power and how long

the electricity is used for.

electrical energy = power x time

Calculating the units of electricity

= 1 kilowatt hour (kWh)



Electricity costs money, which is

why every home has an

electricity meter.

The units of electrical energy are

called kilowatt hours(kWh).

How is electricity paid for?

The cost of an electricity bill is calculated from the number

of units used.

The meter records how much

electricity is used in a house in

units of electrical energy.



The cost of electricity is the number of units of electrical

energy multiplied by the cost per unit.

Example:

How much would 10 units of electricity cost at a price of

9p per unit?

cost = 10units x 9p/unit

cost = number of units x cost per unit

How much does electricity cost?

= 90p



A kettle uses 45.2 kWh of energy.

If electricity costs 10p per unit, how

much does it cost to use the kettle?

Number of units:

Cost of electricity:

Buying electricity example

= 45.2 units

number of units of electricity = number of kilowatt hours

= 452 p or 4.52

= 45.2units x 10p/unit




An iron that operates at a power of 3 kW

for 4 hours uses electricity that costs 8p

per unit. How much does it cost for theelectricity used by the iron in that time?

Number of units:

Cost of electricity:

Buying electricity example

= 12

units

= 12kWh

= 3kW x 4h

number of units of electricity = number of kilowatt hours

= 96p

= 12 units x 8p/unit




Buying electricity calculations



generator A machine that converts kinetic energy intoelectrical energy by induction.

induction Generating a current in a wire by moving thewire in a magnetic field, or by moving a magnet inside a coil

of wire.

kilowatt hour The unit of electrical energy.

power The rate at which energy is transferred.

watt The unit of power. 1 watt = 1 joule of energytransferred every second.

Glossary



Anagrams


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