Edexcel IGCSE Physics : 4 Energy Resources and Energy Transfers

List the methods of energy transfer

mechanically
electrically
by heating
by radiation

List the energy stores

chemical
kinetic
gravitational
elastic
thermal
magnetic
electrostatic
nuclear

State the principle of conservation of energy

Energy cannot be created or destroyed , energy is always conserved and can only be transferred from store to store

State the relationship between efficiency, useful energy output and total energy output

Describe the energy transfers of everyday and scientific devices , including Sankey diagrams

when drawing a Sankey diagram you draw connected arrows

to the left of the arrow you write the total energy

at the end of each arrow you write the store which it has been transferred to

How can thermal energy transfer take place ?

conduction
convection
radiation

How does thermal energy transfer take place by conduction ?

when part of a conductor gets heated

the particles being heated gain kinetic energy and move faster

they therefore collide more often with the particles next to them and transfer kinetic energy to them

this repeats till it is transferred to the whole object

How does thermal energy transfer take place by convection?

when a fluid is heated

the bottom part close to the heat , gains ke and becomes less dense

the warmer fluid then moves upwards as it is less dense

the upper part of the fluid therefore moves down and the heated part moves up

the upper part then cools down and becomes more dense meanwhile the bottom part heats up and becomes less dense

they then switch place

this repeats as a convection current

How does thermal energy transfer take place by radiation?

thermal radiation given off by the sun

infrared waves transfer energy to an object increasing its thermal energy store

the object absorbs infrared waves and heats up

Explain how convection can cause everyday phenomena?

• Off-shore breeze and On-shore breeze ,

• convection currents cause on-shore breeze to happen in the day causing the land to heat up more quickly than the sea( brings hot air to land)

• Convection currents cause off-shore breeze to happen at night causing the land to cool down more quickly than the sea ( takes hot air away from land)

Lightning is caused by convection currents in thunder clouds , causing charged particles to stick together at the bottom of a cloud , resulting in lightning strikes

How is emission and absorption of radiation related to surface and temperature?

• The darker an object is the better it is at absorbing radiation , black is the best

• The lighter an object is the better it is at reflecting radiation , white is the best

• The more matt an object is the better it is at absorbing radiation , matte black is the best

• The more shiny an object is the better it is at reflecting radiation, shiny white is the best
If an object is a good absorber it will be a poor reflector and vice versa

Practical: investigate thermal energy transfer by conduction, convection and radiation

How can unwanted energy transfer be reduced ?

unwanted energy transfer can be prevented by using insulation

e.g. if we put an electrical insulator around a wire it prevents unwanted transfer of electricity

it is the same for heat

State the relationship between work done, force and distance moved

work done = force x distance moved

W = F x d

What is work done ?

work done is energy transferred

State the relationship between gravitational potential energy, mass, gravitational field strength and height

gravitational potential energy = mass × gravitational field strength × height

GPE = m × g × h

State the relationship between kinetic energy , mass and speed

How does conservation of energy produce a link between GPE , KE and work?

The conservation of energy principle states that energy cannot be created or destroyed, only transferred from store to store

Gravitational Potential Energy (GPE): When an object is lifted, work is done against gravity, storing energy as GPE. The higher the object, the more GPE it has.

Kinetic Energy (KE): When the object falls, its GPE converts into KE, increasing its speed as it descends.

Work: The work done to lift the object (force times distance) is equal to the GPE gained. Conversely, as the object falls, the work done by gravity converts GPE into KE.

What is power ?

rate of transfer of energy or the rate of doing work

State the relationship between power, work done, and time taken

power = work done/ time taken

P = W/t

Describe the energy transfers involving generating electricity using wind?

wind causes wind turbines to turn

which causes a generator to rotate

this transfers energy from the kinetic energy store of the air

Describe the energy transfers involving generating electricity using water?

wave power: dams, converts kinetic energy of moving waves to electrical energy by spinning turbines
HEP: stores water in a reservoir , storing energy as GPE ,
when it is released it flows down a pipe gaining KE , water moves turbine/generator

Describe the energy transfers involving generating electricity using geothermal resources?

magma heats earth surface

cold water is pumped underground , where it is heated

turns to steam

energy transfers from thermal energy of rock to thermal energy of water

the steam turns turbines which turn generators generating electric current

Describe the energy transfers involving generating electricity using solar heating systems?

sunlight focused using mirrors onto a furnace

where water is heated to convert it into steam to drive turbines and a generator

Describe the energy transfers involving generating electricity using solar cells?

EM radiation (from sunlight) to the earth is collected by photovaltic cells

when light hits them they create an electric current which transfers energy electrically

Describe the energy transfers involving generating electricity using fossil fuels?

fossil fuels (oil,coal,gas) are burnt in a boiler

converting chemical energy in the fuel to thermal energy of the water

this heats water and it becomes team

this steam is forced under a high pressure over a turbine connected to a generator

Describe the energy transfers involving generating electricity using nuclear power ?

use nuclear fission to create a chain reaction which releases energy

from the nuclear store to kinetic store

then from the kinetic store to the thermal store of the moderator

a coolant is pumped through the reactor which transfers thermal energy from the moderator to the water

which turns to steam which turns a turbine/generator

What are the advantages of electricity production from renewable sources?

little release of CO2
resources are

inexhaustible

HEP short start up time so it can meet rapid demand

zero fuel cost

What are the advantages of electricity production from non-renewable sources?

reliable, not dependent on weather

high capacity to provide lots of energy

nuclear emits large quantities of CO2 or SO2

What are the disadvantages of electricity production from renewable sources?

low capacity don't provide much energy

unreliable as they are weather dependent

high installation cost for power plants

high maintenance cost

large structures can be damaging to visual impact

What are the disadvantages of electricity production from non-renewable sources?

release CO2- greenhouse gas - global warming

release SO2 - acid rain - kill plants and fish

nuclear waste-dangerous

expensive to decommission nuclear planets

mining and drilling for fuel is damaging to local environment

power plants take a long time to start up

resources are finite