AQA GCSE Physics Year 9: Energy

What is a system?

An object or group of objects

What happens when a system changes?

There is a change in the way energy is stored. It is transferred from one store to a different store.

What has kinetic energy?

moving objects

How do you work out the extension of a spring?

Extension = length when there is a force - length when there is no force

If the spring constant is larger is the spring stiffer or less stiff?

Stiffer

What is the gravitational field strength of earth?

9.8 N/kg

What is power?

The rate at which energy is transferred/ the rate at which work is done

What is the power of an energy transfer of 1 joule per second?

1 watt

What is efficiency?

The fraction of the energy supplied to a device which is transferred in a useful form.

How do you calculate percentage efficiency?

Efficiency x 100

Find a good solution to this problem: sound created by machinery causes energy transfer to the surroundings

Cut out noise, e.g by tightening loose parts

Find a good solution to this problem: when a current passes through a wire, the wire's resistance causes it to heat up

Use wires in circuits with as little resistance as possible

Find a good solution to this problem: air resistance causes energy transfer to the surroundings

Streamline the shapes of moving objects to reduce air resistance

Find a good solution to this problem: friction between the moving parts causes heating

Lubricate the moving parts to reduce friction

What are the 4 types of energy transfer?

. Mechanical work

. Electrical work

. Radiation

. By heating

What is mechanical work?

a force moving an object through a distance

What is electrical work?

charges moving due to a potential difference (voltage)

What is heating?

When energy is transferred as objects heat up.

What is radiation?

energy transferred as a wave, e.g light and infrared - light radiation and infrared radiation are emitted from the sun.

What is a renewable energy source?

One that can be replenished as it is used.

What is thermal conductivity?

A measure of how quickly energy is transferred through a material via conduction. The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material.

What do we call thermal energy being transferred by heating in fluids (liquids and gases)?

Convection

What do we call thermal energy being transferred by heating in solids?

Conduction

What is a fossil fuel?

Natural, finite fuel formed from the remains of living organisms, e.g coal, oil and natural gas

What is nuclear fuel?

Radioactive materials, usually uranium or plutonium, used in nuclear reactors.

What is hydroelectricity?

Electricity that is generated by the movement of water

What is geothermal energy?

Energy from the heat of the Earth.

Where does all energy on Earth originally come from?

the sun

What happens when we burn fossil fuels?

They release carbon dioxide, adding to the greenhouse effect, and sulphur dioxide which causes acid rain.

What energy source makes up most of the electricity generated globally?

fossil fuels

Why do fossil fuels make up most of the energy generated globally?

. the high power output they give compared to other energy resources, like wind and water waves

. the existing infrastructure for extracting, transporting and processing fossil fuels - this makes fossil fuels cheaper than setting up new alternatives

What new energy source is on the rise in developed countries? What are it's pros and cons?

. Nuclear fuel

. Can release large amounts of energy compared to fossil fuels and does not emit carbon dioxide

. The radioactive waste produced is difficult to store and dispose of

State the following about coal: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: no

Reliability: high

Energy density: high

Uses: heating, electricity generation, transport

Environmental impact: Air pollution (CO2, carbon monoxide, sulphur dioxide, methane, etc.) and ash particles (carbon)

Other factors: Cheap and running out in about 50 years

State the following about oil: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: no

Reliability: high

Energy density: high

Uses: heating, electricity generation, transport

Environmental impact: Air pollution (CO2, carbon monoxide, sulphur dioxide, methane, etc.) and ash particles (carbon)

Other factors: Cheap and running out in about 50 years

State the following about natural gas: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: no

Reliability: high

Energy density: high

Uses: heating, electricity generation, transport

Environmental impact: Air pollution (CO2, carbon monoxide, sulphur dioxide, methane, etc.) and ash particles (carbon)

Other factors: Cheap and running out in about 50 years

State the following about nuclear: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: no

Reliability: high

Energy density: high

Uses: electricity generation

Environmental impact: Radioactive waste

Other factors: Accidents are deadly, meltdowns can occur, no emissions, expensive

State the following about biomass/biofuels: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: yes

Reliability: high

Energy density: medium

Uses: heating, electricity generation, transport

Environmental impact: CO2 produced but this is offset because the trees use CO2 from the atmosphere so it's carbon neutral

Other factors: Cheap. Collecting enough fuel can be difficult. Can lead to deforestation. Uses land that could be used to grow food.

State the following about solar: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: yes

Reliability: low

Energy density: low

Uses: heating, electricity generation,

Environmental impact: high emissions in production but while running no impact

Other factors: Running costs are low, costs a lot to install, used remotely, dependant on weather

State the following about wind: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: yes

Reliability: low

Energy density: very low

Uses: electricity generation

Environmental impact: Turbines take up space (habitats) but can still be used for farming, harmful to birds

Other factors: no wind = no power, tourist attraction but some think they're an eyesore, interrupt TV signal

State the following about geothermal: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: yes

Reliability: high

Energy density: high

Uses: heating, electricity generation,

Environmental impact: Dangerous gases can sometimes be released, local habitats are altered

Other factors: Running costs are low, can be hard to find suitable areas, triggers earthquakes

State the following about hydroelectricity: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: yes

Reliability: high

Energy density: medium

Uses: electricity generation

Environmental impact: Destroys habitats and plant life

Other factors: Expensive to build

State the following about tidal: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: yes

Reliability: high

Energy density: high

Uses: electricity generation

Environmental impact: Damages marine life and can block sewage

Other factors: Costs are low, only works twice a day and in some suitable places, expensive to build

State the following about wave: renewable, reliable, energy density, uses, environmental impact, other factors

Renewable: yes

Reliability: high

Energy density: low

Uses: electricity generation

Environmental impact: harmful to marine life, could release toxic chemicals

Other factors: Noisy, causes hazards to ships

What are the units for energy?

Joules (J)

What are the units for mass?

kg

What are the units for speed?

m/s

What are the units for extension (of a spring)?

m

What are the units for spring constant?

N/m

What are the units for force (applied)?

newtons (N)

What are the units for gravitational field strength?

N/kg

What are the units for any distance (e.g height)?

m

What are the units for time?

seconds (s)

What are the units for power?

Watts (W)

What are the units for work done?

Joules (J)