Energy Resources and Energy Transfer. Contents Thermal Energy Transfer Thermal Energy Transfer Efficiency Efficiency Energy Resources Energy Resources.

Energy ResourcesEnergy Resourcesand Energy Transferand Energy Transfer

ContentsContents

Thermal Energy TransferThermal Energy Transfer EfficiencyEfficiency Energy ResourcesEnergy Resources Work, Power and EnergyWork, Power and Energy Electromagnetic ForcesElectromagnetic Forces Electromagnetic InductionElectromagnetic Induction

Heat TransferHeat Transfer

A cup of coffee will cool down because it is giving out heat energy into the surroundings

This drink (taken out of the fridge) will warm up because it is taking in heat energy from the surroundings

Heat is transferred in order to equalise the temperatures of the object and its environment

ConductionConduction

Atoms in a substance are always Atoms in a substance are always vibrating. If the substance gets vibrating. If the substance gets hotter, the atoms vibrate more. hotter, the atoms vibrate more. The heat energy is given to the The heat energy is given to the atoms, which makes them move atoms, which makes them move about fasterabout faster

Every time they collide with Every time they collide with another atom, the heat energy another atom, the heat energy is transferredis transferred

This is how heat travels through This is how heat travels through a solida solid

ConvectionConvection

Hot air rises in cold air. Hot Hot air rises in cold air. Hot water rises in cold waterwater rises in cold water

This is called convectionThis is called convection When hot air rises, colder air When hot air rises, colder air

has to move in to replace ithas to move in to replace it Convection cannot happen in Convection cannot happen in

solids, as the atoms aren't able solids, as the atoms aren't able to move around to move around

RadiationRadiation

Hot objects radiate heat to their Hot objects radiate heat to their colder surroundingscolder surroundings

Black and dull surfaces emit and Black and dull surfaces emit and absorb radiation wellabsorb radiation well

White and shiny surfaces do not White and shiny surfaces do not emit radiation well and reflect emit radiation well and reflect radiation instead of absorbing itradiation instead of absorbing it

InsulationInsulation

Air can convect the heat energy Air can convect the heat energy away from a house if it is able to away from a house if it is able to move. If the air is trapped in move. If the air is trapped in small spaces it can't move so it small spaces it can't move so it doesn't convect the heat energydoesn't convect the heat energy

Fibreglass keeps the air stillFibreglass keeps the air still Trapped air Trapped air insulatesinsulates heat by heat by

not allowing it to escapenot allowing it to escape

Double glazing works in this wayDouble glazing works in this way

PowerPower

Which boils quicker?Which boils quicker?Kettle with high power ratingKettle with high power rating

oror Kettle with low power ratingKettle with low power rating

Power = how quickly the energy is transferredPower = how quickly the energy is transferred(from electrical to heat energy)(from electrical to heat energy)

High power = Kettle heats up quicklyHigh power = Kettle heats up quicklyLow power = Kettle heats up slowlyLow power = Kettle heats up slowly

PowerPower

The power rating of a light bulb...

Power = how much energy is given to an appliance per unit of time

Power (Watts) = voltage x current

P

IV

Cost of ElectricityCost of Electricity

1 unit = 1kWh Number of units = power rating x time used

EfficiencyEfficiency

Power = energy transfer per secondPower = energy transfer per second

Power = energy transferred/time takenPower = energy transferred/time taken

(W) (W) (J)(J) (sec)(sec)

During a movement or change of state (etc.) energy is During a movement or change of state (etc.) energy is usually lost as heat energy to the surroundingsusually lost as heat energy to the surroundings

The energy inputted is therefore always higher than The energy inputted is therefore always higher than the useful energy taken outthe useful energy taken out

Efficiency = (useful energy out/energy in) x 100 = %Efficiency = (useful energy out/energy in) x 100 = %

E

TP

Non-Renewable FuelsNon-Renewable Fuels

All power stations generate electricity:All power stations generate electricity:

- Fuel is used to produce heat energy- Fuel is used to produce heat energy

- The heat energy heats water and turns it into steam- The heat energy heats water and turns it into steam

- The steam is pushed at high pressure along pipes to - The steam is pushed at high pressure along pipes to the turbinesthe turbines

- The steam makes the turbines spin, turning a - The steam makes the turbines spin, turning a generator which then produces electricitygenerator which then produces electricity

- The electricity is then supplied to houses, factories - The electricity is then supplied to houses, factories and schools via the national gridand schools via the national grid

Non-renewable (fossil) fuels are oil, gas and coal Non-renewable (fossil) fuels are oil, gas and coal

Nuclear FuelsNuclear Fuels

Uranium is the fuel used in many nuclear power Uranium is the fuel used in many nuclear power stationsstations

Uranium is not burnt like coal or gas but undergoes Uranium is not burnt like coal or gas but undergoes nuclear fissionnuclear fission

Atoms of uranium are split up which releases large Atoms of uranium are split up which releases large amounts of energyamounts of energy

Nuclear fission produces harmful radiation so people Nuclear fission produces harmful radiation so people are scepticalare sceptical

Waste from these reactions is also radioactiveWaste from these reactions is also radioactive Accidents are serious but very rareAccidents are serious but very rare

Electromagnetic ForcesElectromagnetic Forces

A current (I) has a magnetic field (B) around itA current (I) has a magnetic field (B) around it A wire has a circular magnetic field around itA wire has a circular magnetic field around it

If the current changes direction, so does the fieldIf the current changes direction, so does the field

Electromagnetic ForcesElectromagnetic Forces

Magnets attract magnetic materials using a magnetic Magnets attract magnetic materials using a magnetic fieldfield

The magnetic field surrounds the magnet, and gets The magnetic field surrounds the magnet, and gets weaker as the distance from the magnet increasesweaker as the distance from the magnet increases

Magnets should be called permanent magnetsMagnets should be called permanent magnets

the magnetism is always therethe magnetism is always there

Electricity makes a magnet much strongerElectricity makes a magnet much stronger This can be turned on and offThis can be turned on and off

Electromagnetic ForcesElectromagnetic Forces

Magnets pick up paper clips etc.Magnets pick up paper clips etc.

Electromagnets pick up cars etc.Electromagnets pick up cars etc.

weak

strong

The magnetic field around a coil electromagnet can be The magnetic field around a coil electromagnet can be increased by:increased by:

- Increasing the current flowing through the wire- Increasing the current flowing through the wire

- Adding loops on the coil (loops are long lengths of - Adding loops on the coil (loops are long lengths of wire)wire)

- Placing an iron or steel core inside the coil- Placing an iron or steel core inside the coil

Basic electromagnetBasic electromagnet

Electromagnetic ForcesElectromagnetic Forces

The Motor EffectThe Motor Effect::

- When two magnets are placed close to each other, - When two magnets are placed close to each other, they the fields affect each other produce a forcethey the fields affect each other produce a force

If a wire carrying a current is placed inside this If a wire carrying a current is placed inside this magnetic field, a force is produced. This is called the magnetic field, a force is produced. This is called the motor effectmotor effect

The direction of the force will depend on the direction The direction of the force will depend on the direction of the magnetic field and the direction of the current in of the magnetic field and the direction of the current in the fieldthe field

Electromagnetic ForcesElectromagnetic Forces

Fleming’s Left Hand RuleFleming’s Left Hand Rule::

- When creating a force, use Fleming’s LH Rule to - When creating a force, use Fleming’s LH Rule to determine in which way the motor will spindetermine in which way the motor will spin

- -

Electromagnetic ForcesElectromagnetic Forces

We can increase the force produced by:We can increase the force produced by:

- increasing the current- increasing the current

- increasing the number of coils- increasing the number of coils

- increasing the magnetic field strength (stronger - increasing the magnetic field strength (stronger magnet)magnet)

Electromagnetic ForcesElectromagnetic Forces

Electromagnetic InductionElectromagnetic Induction

• When a magnet is moved into a coil, an electrical current is induced

• When the magnet stops,the induced current stops

• When the magnet reverses, the electrical current reverses

Electromagnetic InductionElectromagnetic Induction

Increase the voltage? … 3 ways…

1. Stronger magnet

2. Speed of magnet

3. Number of coils

TransformersTransformers

TransformersTransformers

4 coils produce 10V 8 coils produce 20V

Power stations step-up the voltage to reduce energy losses(but v high voltage)

Pylons to houses step-down the voltage to reduce risk of electrocution

TransformersTransformers

SummarySummary

Thermal energy is transferred by conduction, Thermal energy is transferred by conduction, convection and radiationconvection and radiation

Efficiency % = (useful output/total input) x 100Efficiency % = (useful output/total input) x 100 Fossil fuels are widely used energy resources but Fossil fuels are widely used energy resources but

these are non-renewablethese are non-renewable E = PxT, P = V x I, uE = PxT, P = V x I, units = power (kW) x time (hr) Electromagnetic forces are used to create Electromagnetic forces are used to create

movementmovement Movement is used to create voltage using Movement is used to create voltage using

electromagnetic inductionelectromagnetic induction