AQA GCSE Triple Science - Physics

Name 8 energy stores

Thermal
Kinetic
Gravitational potential
Elastic potential
Chemical
Magnetic
Electrostatic
Nuclear

What are the four ways that energy is transferred?

Mechanically, electrically, by heating, by radiation

What is a closed system?

Neither energy nor matter can enter or leave. The net change in the total energy of a closed system is always zero.

What does work done mean?

Energy transferred

What happens to an object's g.p.e. store and kinetic energy when it falls?

The object's gravitational potential energy store is transferred to its kinetic energy store.

What is the equation for kinetic energy?

Kinetic energy = 0.5 x mass x (velocity)^2

What is the equation for gravitational potential energy?

Gravitational potential energy = mass x gravitational field strength x height

What is specific heat capacity?

The amount of energy needed to raise the temperature of 1kg of a substance by 1 degree C.

What is the conservation of energy principle?

Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed

Describe the transfer of energy in a closed system for a cold spoon and hot soup. Assume the flask is a perfect thermal insulator.

Energy is transferred from the thermal energy store of the soup to the useless thermal energy store of the spoon (causing the soup to cool down slightly). Energy transfers have occurred within the system, but no energy has left the system - so the net change in energy is zero.

What is power?

The rate of energy transfer or the rate of doing work

What is energy measured in?

Joules (J)

What is power measured in?

watts

What is one watt?

1 joule of energy transferred per second

What are the two equations for calculating power?

Power(W) = energy transferred(J) / time(s)
Power(W) = work done(J) / time(s)

What is conduction?

conduction is the process where vibrating particles transfer energy to neighbouring particles

How does conduction happen?

The thermal energy in the object causes the particles to vibrate more and collide with each other. This causes the energy to be transferred between particles' kinetic energy stores

In what states does convection occur?

Liquid and gas

What is convection?

Convection is where energetic particles move away from hotter to cooler regions

How does convection happen?

Unlike in solids, the particles are able to move. When you heat a region of a gas or liquid, the particles move faster and the space between individual particles increases. This causes the density to decrease. The warmer regions will rise above the cooler, denser regions, and the process repeats.

What do lubricants do?

Reduce the friction between objects' surfaces when they move. They are usually liquids so they can flow easily between objects and coat them.

How do you prevent energy losses through heating in a house?

Have thick walls made from a material with low thermal conductivity
Use thermal insulation

Give four examples of thermal insulation and what they do

Cavity walls - inner and outer wall with an air gap between them. This reduces conduction through the walls
Loft insulation - fibreglass wool is often used as it has pockets of trapped air. It helps convection currents from being created
Double glazed windows - two sheets of glass with an air gap between them. This prevents conduction through the windows
Draught excluders - around doors and windows to reduce energy transfers by convection

What 3 ways are there to improve the efficiency of energy transfers?

Insulating objects
Lubricating them
Making them more streamlined

What are the two equations for calculating efficiency?

Efficiency = useful output energy transfer / total input energy power
Efficiency = useful power output / total power output

What are the three main fossil fuels?

Coal
Oil
(Natural) Gas

What are two disadvantages of fossil fuels?

They will run out
They damage the environment

What are the 7 renewable energy resources?

Solar
Wind
Waves
Hydro-electricity
Bio-fuel
Tides
Geothermal

What are two disadvantages of renewable energy resources?

Don't provide much energy
Some are unreliable as they depend on the weather

Give some transportation methods and which energy resources they use

Vehicles - petrol and diesel from oil
Steam trains - coal is used to boil water to produce steam
Vehicles - biofuels, or biofuels and petrol/diesel

How are non-renewable energy resources used for heating?

Natural gas is used to heat water which is then pumped into radiators
Coal is burnt in fireplaces
Electric heaters for heating

How are renewable energy resources used for heating?

Geothermal pump is used to heat buildings
Solar water heaters heat water which is then pumped into radiators in the building
Burning biofuels or using electricity from renewable resources can also be used

How does a wind turbine work?

The turbine turns a generator which produces electricity

On average what percentage of the time do wind turbines produce electricity?

70-85

Give 5 disadvantages of wind turbines

Spoil the view
Can be very noisy
Cannot increase supply when there's extra demand
Turbines stop when there is no wind or it is too strong
Initial costs are quite high

Give 4 advantages of wind turbines

No pollution
No fuel costs
Minimal running costs
No permanent damage to the landscape

Where are solar cells most often used?

Calculators and watches

Give 4 advantages of solar cells

No pollution
Very reliable in sunny countries
Energy is free
Running costs are almost nil

Give 1 disadvantage of solar cells

Initial costs are high

Where is geothermal power possible?

Volcanic areas where the hot rocks lie near to the surface

Give three advantages of geothermal power

Can generate electricity or heat buildings directly
Very few environmental problems
Reliable resource

Give 2 disadvantages of geothermal power

There aren't very many suitable places
The cost of building a plant is high

Give 4 advantages of hydro-electric power

Provides an immediate response to an increased demand for electricity
Reliable
No fuel costs
Minimal running costs

Give 3 disadvantages of hydro-electric power

Possible loss of habitat
Reservoirs look unsightly
The flooding of the valley has an impact on the environment as rotting vegetation releases methane and carbon dioxide

Give three advantages of wave power

No pollution
No fuel costs
Minimal running costs

Give 5 disadvantages of wave power

Disturbs the sea bed
Spoils the view
Hazard to boats
Initial costs are high
Fairly unreliable as they stop working when the wind drops

What are tidal barrages?

Big dams built across river estuaries, with turbines in them. As the tide comes in,it fills up the estuaries. The water is then allowed out through turbines at a regulated speed

Give 5 advantages of tidal barrages

No pollution
Reliable
No fuel costs
Minimal running costs
Has the potential for generating lots of energy

Give 2 disadvantages of tidal barrages

Spoils the view
Alters the habitat of the wildlife

What are bio-fuels made from?

Plants and waste

Give 2 advantages of bio-fuels

Carbon neutral
Reliable

Give 3 disadvantages of bio-fuels

Cost to refine bio-fuels so they can be used is high
In some areas, large areas of forest have been cleared to make room for bio-fuel crops
Some animals have lost their habitats due to planting these crops

Give 6 environmental problems caused by non-renewable resources

Carbon dioxide is released which causes global warming
Sulfur dioxide causes acid rain
Views can be spoilt by coal mining or power plantns
Oil spillages
Nuclear waste is dangerous and difficult to dispose of
Nuclear power carries the risk of a catastrophe

What is the national grid?

A system of cables and transformers that covers the UK and connects power statons to consumers. It transfers electrical power from power stations anywhere on the grid to anywhere else on the grid where it is needed

When does the demand for electricity increase?

When people get up in the morning
Coming home from school or work
When it gets dark or cold outside
Popular events being shown on TV

How do you transmit lots of power through the national grid?

High potential difference or a high current

What is the problem with using a high current to transmit lots of power?

Lots of energy is lost as the wires heat up

For a given power, what does increasing the pd do?

Decreases the current, which decreases the energy lost by heating the wires and the surroundings

How is potential difference changed?

By transformers

How do transformers work?

They step the potential difference up at one end for efficient transmission and then bring it back down again to safe, usable levels at the other end