SP3 - Conservation of Energy

Question 1

What are the energy stores and transfers?

Answer 1

Stores - thermal, kinetic, chemical, nuclear, gravitational potential, elastic potential
Transfers - by sound, by light, by heating, by electricity, by forces

Question 2

What is the law of conservation of energy?

Answer 2

Energy cannot be created or destroyed, only transferred from one form to another. In a closed system, the total energy input is equal to the total energy output.

Question 3

What are energy flow diagrams?

Answer 3

Energy flow diagrams are diagrams used to show the transfers of energy in a system. They show the store(s) the energy started off in, the store(s) it ends up in, and the way in which energy is transferred from one store to another.

Question 4

What are Sankey diagrams?

Answer 4

Sankey diagrams show the amount of energy inputted and the amount of energy transferred usefully and wastefully. They can be used to calculate efficiency.

Question 5

What is efficiency?

Answer 5

Efficiency is a measure of how much of the energy/power supplied is transferred usefully.

Efficiency = useful energy transferred / total energy supplied

OR…. Efficiency = useful power transferred / total power supplied

Question 6

How can you increase the efficiency of a system?

Answer 6

Lubrication - reduces frictional forces between objects in a system (e.g. oiling a bike chain makes it easier to ride)
Thermal Insulation - reduces heat loss by conduction and convection

Question 7

What methods do we use to keep houses warm?

Answer 7

Cavity wall insulation - two layers of wall with a gap in the middle filled with insulating foam which stops energy loss by conduction and convection.
Double glazing - two panes of glass with sealed air between them which stops heat transfer by conduction (as particles in air are very spread out)
Carpets - reduces heat loss through the floor
Loft insulation - reduces heat loss through the roof.

Question 8

What is conduction?

Answer 8

Conduction is a method of heat transfer. One part of a material is heated, which causes its particles to gain kinetic energy and vibrate more, causing the particles next to them to vibrate as well due to an increased number of collisions. The vibrations are passed through the material and the heat is distributed evenly throughout it.

Question 9

What is convection?

Answer 9

Convection is a method of heat transfer. Part of a fluid is warmer than another, so it rises, but as it rises it cools, causing it to fall again. It heats up so rises once more. This is called a convection current.

Question 10

What is radiation?

Answer 10

Radiation is a method of heat transfer. Heat is transferred by infrared waves, and so this method of heat transfer does not require particles, so can happen through a vacuum (e.g. heat from sun reaches Earth by radiation).

Question 11

What is gravitational potential energy?

Answer 11

Gravitational potential energy (GPE) is the energy stored by an object because of its position in a gravitational field.

GPE (J)= m(kg) x g (N/kg) x h (m)

Question 12

What is kinetic energy?

Answer 12

Kinetic energy is the energy stored in moving objects.

KE (J) = 1/2 x m(kg) x v^2(m/s)

Question 13

What are non-renewable resources?

Answer 13

Non-renewable resources are energy sources which will run out one day because we are using them faster than they can be produced.

Examples include fossil fuels (coal, oil, natural gas) and nuclear power.

Question 14

What are the pros and cons of nuclear power?

Answer 14

Pros - produces lots of energy per kg of fuel, produces no CO2, can respond to demand
Cons - danger of nuclear disasters, dangerous nuclear waste is created with a very long half-life.

Question 15

What are the pros and cons of fossil fuels?

Answer 15

Pros - reliable and can respond to demand, lots of energy per kg of fuel
Cons - non-renewable, burning fossil fuels contributes to climate change (CO2) and acid rain (SO2)

Question 16

What are renewable resources?

Answer 16

Renewable resources are energy sources which will never run out because they are being produced at the same rate as or faster than we are using them.

Examples include solar, wind, wave and hydroelectric power.

Question 17

What is solar power + pros and cons

Answer 17

Solar cells convert heat energy from the Sun directly into an electrical current.

Pros - renewable, does not produce CO2, costs of running a solar farm are low.

Cons - not reliable as only produces energy when it’s sunny, solar farms take up a lot of space, it is expensive to build solar farms.

Question 18

What is wind power + pros and cons

Answer 18

Wind power is generated when the wind blows. The wind turns a turbine, which turns a generator, which produces electricity.

Pros - renewable, does not produce CO2, costs of running a wind farm are low.

Cons - not reliable as only produces energy in windy conditions, it is expensive to set up a wind farm, does not produce as much energy as non-renewable sources

Question 19

What is geothermal power + pros and cons

Answer 19

Hot rocks heat water, which turns into steam and turns a turbine, which turns a generator, which produces electricity.

Pros - reliable as is not weather dependent, renewable, does not produce CO2

Cons - location dependent (only used in areas of volcanic activity), costs a lot to set up geothermal power stations

Question 20

What is hydroelectric power + pros and cons

Answer 20

Dams trap water high up (so stores GPE), forming reservoirs. Water is let through the dam, which turns a turbine, which turns a generator, which produces electricity.

Pros - reliable and can respond to demand, renewable, doesn’t produce CO2

Cons - location dependent (can only build hydroelectric dams where water naturally goes from high to low), can cause damage to local habitats and may force people to relocate.

Question 21

What is tidal power + pros and cons

Answer 21

Tidal barrages in river estuaries produce electricity as when the tides come in, they trap water on one side of the dam and slowly allow it through, which turns a turbine, which turns a generator, which produces electricity.

Pros - renewable, does not produce CO2, reliable (as tides always happen twice a day)

Cons - not many places are suitable for tidal barrages, may damage birds/fish + ecosystems.

Question 22

What are bio-fuels + pros and cons

Answer 22

Bio-fuels can be used in the same way as fossil fuels. They are made by burning animal waste / plants. They are thought to be carbon neutral because when the plants are burned, they produce the same amount of CO2 as they took in while growing.

Pros - renewable, reliable, substitute for fossil fuels

Cons - not really carbon neutral due to transport and harvesting, takes up lots of space which could be used for farming.