GCSE AQA Physics - Energy

Law of Conservation of Energy

Energy cannot be created or destroyed, only transferred between energy stores.

8 Energy Stores

Thermal (Internal), Kinetic, Gravitational Potential, Elastic, Chemical, Electrostatic, Nuclear, Magnetic

System

An object or group of objects.

Closed System

A system in which no matter or energy can enter or leave.

What happens when a system changes?

Energy is transferred

How can energy be transferred?

Mechanically (a force doing work), electrically (work done by a moving charge), by heating or by radiation.

Work done

Energy transferred when a force moves an object along a distance or when a current flows.

Heating

Transferring thermal energy from one object to another with a lower temperature.

Kinetic Energy

Energy an object has because it is moving.

Gravitational Potential Energy

Energy due to an object’s position in a gravitational field.

Elastic Potential Energy

Energy an object has when it is squashed or stretched.

Limit of proportionality

The point beyond which the force applied to an elastic object is no longer proportional to the extension.

Specific Heat Capacity

The amount of energy required to raise the temperature of 1kg of a substance by 1°C.

Power

Rate of energy transfer or rate of work done.

Conduction

Energy transfer by vibrating particles colliding onto neighbouring particles.

Convection

Energy transfer by energetic particles moving from a hotter to a colder region.

Specific Heat Capacity unit

J/kg°C

Power unit

watt

Describe the energy changes involved when a ball is thrown upwards and then returns to it’s starting position

• Upwards - KE is converted to GPE

• Peak - Maximum GPE, no KE

• Downwards - GPE is converted to KE

Describe energy transfers in a bungee jump

• Falling - GPE converts to KE

• Chord tightens - KE converts to EPE

• Lowest point - initial GPE = final EPE

Friction

The force that opposes an object’s motion.

Dissipated/wasted energy

Energy being stored in a way that is not useful

Lubricants

Liquids that reduce friction between the surfaces of two objects.

Insulation

Reducing rate of energy transfer through heating

Thermal conductivity

The rate of energy transfer by heating through conduction.

Thermal Insulator

A material with a lower thermal conductivity

How can we insulate a home? (4)

• Cavity wall insulation

• Loft insulation

• Double glazing

• Draught excluder

Factors affecting energy transfer through a material

• Material’s thermal conductivity

• Temperature difference between 2 sides of material

• Material’s thickness

Efficiency =

Useful energy output / Total energy input

Non-Renewable energy resources

Energy resources that will run out one day.

Renewable energy resources

Energy resources that will never run out.

Examples of non-renewable energy resources

Coal, Oil, Natural Gas, Nuclear

Examples of renewable energy resources

Solar, wind, wave, hydroelectric, tidal, geothermal, biofuel

Uses of energy resources

Transport, electricity and heating

Characteristics of renewable (4)

• Will never run out

• Smaller environmental impact

• Provide less energy

• Less reliable if they depend on weather

Characteristics of non-renewable (4)

• Will run out

• Greater environmental impact

• Reliable

• Relatively abundant

Describe the environmental impact of fossil fuels (2)

• Carbon dioxide causes global warming

• Sulphur dioxide leads to acid rain

Advantages of Nuclear (2)

• Large amount of energy for small quantities of fuel

• No greenhouse gas emissions

Disadvantages of Nuclear (3)

• Nuclear waste is harmful and must be stored for centuries

• Non-Renewable

• Nuclear accidents

Disadvantages of Biofuel (3)

• Plants release CO2 when burned

• Land is destroyed

• Reduces land available

Advantages of Tidal (2)

• Renewable

• Cheap to run (tides are natural)

Disadvantages of hydroelectric (2)

• Requires flooding - destroys habitats

• High initial cost