EnergyEnergy

W. Richards

Worthing High School

The 9 types of energy…The 9 types of energy…

Kinetic (movement)

Sound

Light

Heat

Nuclear

Electrical

Chemical

Gravitational potential

Elastic potential

ConvectionConvection

Convection is all about when a gas or liquid (“fluid”) moves and carries heat with it. When the fluid is heated it ____________. This means that it will become less __________ than the colder fluid around it. Because of this the warmer fluid will try to “_______” over the colder fluid, and this is why warm air rises. This is called a convection ___________. This is how heat reaches us from the ___________ in this room.

Words to use: expands, radiators, dense, heated, current, float

Some questions on convection…Some questions on convection…

1) Freezers in supermarkets are often left open to the air. Explain why the food does not melt easily.

2) Explain why a hot air balloon rises in the air.

3) Explain why an ice cube floating at the top of a drink will cool al of the drink.

ConductionConductionConduction is all about when heat is transferred along a

_________. The heat is passed on by ___________ in the molecules. These vibrations get bigger when the solid has more energy (i.e. when it is being __________).

There are two main differences to convection:

1) Convection happens in _________ (i.e. liquids and gases), whereas conduction mainly happens in solids,

2) In __________ the fluid moved around and carried the heat with it, whereas in _________ the solid doesn’t actually move – the heat is passed on by the particle vibrations.

Words – vibrations, conduction, heated, solid, convection, fluids

RadiationRadiationRadiation is when heat moves around in electromagnetic _________ like light does. Any hot object will emit heat radiation – the hotter it is, the more radiation it emits. This type of radiation is called __________, and to much of it will cause _________. Dark, matt colours will absorb AND emit the _____ infra-red radiation, and light, shiny colours will ________ it.

The main difference between radiation and the other two types of heat transfer is that conduction and convection could only happen in solids, liquids or gases, whereas radiation will happen through an _____ _____. This is just as well, as otherwise we wouldn’t be able to get any heat from the ___.

Words – sun, reflect, infra-red, waves, most, empty space, sunburn

CCR definitionsCCR definitions

This is when heat is passed through a solid by vibrations in the molecules.

This is when heat is transferred by infra-red waves.

This is when a fluid is heated and expands, causing it to rise and carry the heat with it.

A unit of energy

A unit of electricity (energy)

Calculating the cost of Calculating the cost of electricityelectricity

Clearly, this depends on two things: the POWER RATING of the appliance and HOW LONG you leave it on for. Electricity is measured in “units”, also called “kilowatt hours” (kWh).

To work out how much something would cost use two steps:

1) Find out how many units have been used:

No. of units = Power rating x Time appliance is on for

(in kWh) in kW in hours

2) Multiply the number of units by how much each one costs:

Cost of electricity = no. of units used x cost of each unit

in pence in kWh in pence

Energy and PowerEnergy and PowerThe POWER RATING of an appliance is simply how much energy it uses every second.

In other words, 1 Watt = 1 Joule per second

E

TP

E = Energy (in joules)

P = Power (in watts)

T = Time (in seconds)

Gravitational Potential Gravitational Potential EnergyEnergy

To work out how much gravitational potential energy an object gains when it is lifted up we would use the simple equation…

GPE = Weight x Height raised

In Joules (J) in Newtons (N) in metres (m)

Some example Some example questions…questions…

How much gravitational potential energy have the following objects gained?:

1) A brick that weighs 10N lifted to the top of a house (10m),

2) A 10,000N car lifted by a ramp up to a height of 2m,

3) A 700N person lifted up 50m by a ski lift.

How much GPE have the following objects lost?:

1) A 2N football dropping out of the air after being kicked up 30m,

2) A 0.5N egg falling 10m out of a bird nest,

3) A 10,000N car falling off its 2m ramp.

EfficiencyEfficiency

Efficiency is a measure of how much USEFUL energy you get out of an object from the energy you put INTO it.

Efficiency = Useful energy given out by the device

Energy put into it

e.g. if 2000 joules of electrical energy are put into a kettle and 500 joules of heat energy are gained from it, its efficiency is 500/2000 x 100% = 25%

x100%

Some examples of Some examples of efficiency…efficiency…

1) 5000J of electrical energy are put into a motor. The motor converts this into 100J of movement energy. How efficient is it?

2) A laptop can convert 400J of electrical energy into 240J of light and sound. What is its efficiency? Where does the rest of the energy go?

3) A steam engine is 50% efficient. If it delivers 20,000J of movement energy how much chemical energy was put into it?

Renewable vs. non-renewable Renewable vs. non-renewable fuelsfuels

A ________ energy source is one that can be _______ (“renew = make again”), e.g. _____, solar power etc.

A ___________ energy source is one that when it has been used it is gone forever. The main examples are ____, oil and gas (which are called ______ ____, as they are made from fossils), and nuclear fuel.

Words to use – non-renewable, coal, renewable, fossil fuels, wood, renewed

Power stationsPower stations

Cooling tower

Turbine

Generator

Transformer

Boiler

What does What does each part each part

do?do?

The boiler is where the fuel is burnt to boil water

The steam from the boiler is used to turn a turbine

The turbine is connected to the generator, which acts like a dynamo – it generates electricity out of movement

The steam is cooled down and turned back into water in the cooling tower

““Start up” timesStart up” times

Each type of power station differs in how long it takes to “start it up”:

Shortest time

Longest time

Gas

Oil

Coal

Nuclear

PollutionPollution

When a fuel is burned the two main waste products are _____ dioxide and ________ dioxide.

Carbon dioxide destroys the ____ layer and helps to cause the _______ ______.

Sulphur dioxide, when dissolved in ________, causes ______ _____.

Words – sulphur, ozone, carbon, acid rain, greenhouse effect, rainwater

To conclude…To conclude…Power stations using coal, oil, gas or nuclear fuels can whack out the energy, BUT…

Problem 1 – Fossil fuels and nuclear sources will RUN OUT

Problem 2 – Burning fossil fuels will pollute the atmosphere

Problem 3 - Nuclear plants run the risk of contamination and the cost of shutting them down (“decommissioning”) is very high

So what’s the solution?

Other ways of generating Other ways of generating electricity…electricity…

Can we drive the turbine DIRECTLY?

Other ways of generating Other ways of generating electricity…electricity…

Wind

TidalWave

Hydro-electric

What are the disadvantages of these What are the disadvantages of these renewable forms of energy?renewable forms of energy?

Source Disadvantages

Wind

Wave

Tidal

Hydroelectric

Source Disadvantages

Wind Depends on weather, visual pollution, difficult to “store”

Wave Harms wildlife, depends on size of waves, depends on weather

Tidal Depends on size of tides, harms wildlife, visual pollution

Hydroelectric Habitats can be destroyed, only good as a “short term” supply

Also, these sources all have high setting up costs

Other options…Other options…

Geothermal energy – water is heated using heat given off by radioactive rocks underneath the surface of the Earth

Solar energy – using solar panels light can be converted straight into electricity

Matching supply and Matching supply and demand…demand…

“Baseline” power stations

Hydroelectric power station might “kick in” here

Further renewable Further renewable problems…problems…

Although renewable fuels are free, the energy we get from them is “dilute”. This means that we have to spend a lot of money on generators to make them worthwhile.

This is why solar panels are only used in small things (like calculators) or extremely remote locations (like satellites).

SummarySummary

Renewable sources of energy are cheaper, cleaner and will not run out. However, they are incapable of providing all the energy we need, so we will have to

go on burning fossil fuels for now.