Topic 3 - Conservation of energy

Question 1

What is meant by conservation of energy?

Answer 1

Conservation of energy means energy is never created or destroyed

Question 2

What do energy transfer diagrams show?

Answer 2

You can draw diagrams to show energy transfer. The boxes represent energy stores and the arrows show energy transfers

Question 3

What are the energy stores?

Answer 3

• kinematic (anything moving)
• thermal (any object)
• chemical (can release energy by a chemical reaction)
• gravitational potential (anything in gravitational field)
• elastic potential (anything stretched)
• electrostatic (two charges that attract or repel)
• magnetic (two magnets that attract or repel)
• nuclear (atomic nuclei release energy from this store in nuclear reactions)

Question 4

What is a kinetic energy store?

Answer 4

A moving object has energy in its kinematic store. The greater an objects mass and the faster its speed, the more energy it has in its kinetic energy store

Question 5

What is gravitational potential energy?

Answer 5

An object at a height has energy in its gravitational potential energy store.

Question 6

What is a closed system?

Answer 6

A closed system is a system that can be treated completely on its own, without any energy being exchanged to or from the surroundings.

Question 7

What are the energy transfers?

Answer 7

• Mechanically
• Electrically
• By heating
• By radiation

Question 8

Where there are energy transfers in a closed system…?

Answer 8

There is no net change to the total energy in that system

Question 9

When do mechanical processes become wasted?

Answer 9

Mechanical processes become wasted when they cause a rise in temperature so dissipating energy in heating the surroundings

Question 10

What happens in all system changes?

Answer 10

In all system changes energy is dissipated so that it is stored in less useful ways

Question 11

What is lubrication?

Answer 11

Lubrication reduces energy transferred by friction and reduces the amount of unwanted energy. For objects that are touching each other, lubricants can be used to reduce the friction between them. Lubricants can flow easily between objects and coat them (oils)

Question 12

What is thermal insulation?

Answer 12

Insulation reduces the amount of unwanted energy.

Question 13

What are effects of the thickness and thermal conductivity of the walls of a building on its rate of cooling?

Answer 13

In a building, the lower the thermal conductivity of its walls, the slower the rate of energy transfer through them. The air gap in cavity walls reduces the amount of energy transferred by conduction. Thicker walls slow down the rate of energy transfer. The building will cool slowly.

Question 14

What is meant by efficiency?

Answer 14

Efficiency is the usefulness of energy. Energy is only useful when it is transferred from one store to a useful store.

Question 15

What does the conservation of energy principle mean?

Answer 15

Total energy input = useful energy output + wasted energy

Question 16

The less energy wasted…?

Answer 16

The more efficient a device is said to be

Question 17

What do Sankey Diagrams show?

Answer 17

How efficient a device is. They show the total energy supplied to device, energy wasted and useful energy transferred

Question 18

What are non-renewable energy resources?

Answer 18

resources that will run out one day

Question 19

What are examples of non-renewable energy resources?

Answer 19

• Fossil fuels (coal, oil and gas)

- Nuclear Energy

Question 20

What are the advantages of non-renewable energy resources?

Answer 20

They’re reliable, there’s still plenty of fuel around to meet current demand. Cost to extract fossil fuels is relatively low. Fossil fuel power plants are cheap to build and run.

Question 21

What are the disadvantages of non-renewable energy?

Answer 21

Nuclear power plants are costly to build. Fossil fuels are slowly running out. They create environmental problems - fossil fuels release co2 which ads to the greenhouse effect and contributes to global warming. Burning coal releases sulfur dioxide which causes acid rain. Nuclear waste is hard to dispose of

Question 22

What are renewable resources?

Answer 22

Resources that will never run out

Question 23

What are examples of renewable resources?

Answer 23

• Bio-fuels
• Wind
• The sun (solar)
• Hydro-electricity
• Tides

Question 24

Whats are advantages of renewable resources?

Answer 24

• They won’t run out

- There damage isn’t as bad as non renewable resources’

Question 25

Whats the disadvantage of renewable resources?

Answer 25

• They don’t provide much energy and some of them are unreliable because they depend on the weather

Question 26

What are bio-fuels?

Answer 26

Bio-fuels are made from plants and waste. They’re renewable resources that can be burnt to make electricity or run cars.

Question 27

What is wind power?

Answer 27

Wind turbines produce electricity. They prevent pollution and are a renewable resource.

Question 28

What are solar cells?

Answer 28

Solar cells are made from materials that use energy transferred by light to create an electric current. They can power electric road signs and satellites. They prevent pollution. Renewable resource

Question 29

What is hydro-electricity?

Answer 29

Producing hydro-electricity usually involves flooding a valley by building a big dam. Rainwater is caught and allowed out through turbines. It prevents pollution. It can immediately respond to increased electricity demand. Renewable resource

Question 30

What are tidal barrages?

Answer 30

Tidal barrages are big dams built across river estuaries with turbines in them. As the tide comes in it fills up the estuary. The water is then let out through turbines at a controlled speed to generate electricity. Prevents pollution. Renewable.

Question 31

What are reasons for a change in the type of energy resources we use?

Answer 31

• changes in cost
• breakthrough in technology
• understanding of how they affect the environment
• reliability

Question 32

How can you make something more efficient?

Answer 32

By lubrication and thermal insulation. Decreasing the amount of wasted energy means that a higher proportion of the supplied energy is transferred to useful stores, so the efficiency of the process is increased

Question 33

What are the changes in the way energy is stored when an object is projected upwards or up a slope?

Answer 33

The object does work against the gravitational force, so energy is transferred mechanically from the kinetic energy store of the object to its gravitational potential energy store

Question 34

What are the changes in the way energy is stored when a moving object hits an obstacle?

Answer 34

An object has energy in its kinetic energy store. Some of this is transferred mechanically to the object’s kinetic energy store. Some energy is also transferred mechanically to the thermal energy stores of both objects that hit together. The rest is carried away by sound

Question 35

What are the changes in the way energy is stored when an object is being accelerated by a constant force?

Answer 35

Gravity does work on the object, so the object constantly accelerates towards the ground. Energy is transferred mechanically from the object’s gravitational potential energy store to it’s kinetic energy store

Question 36

What are the changes in the way energy is stored when a vehicle is slowing down?

Answer 36

Energy in the kinetic energy store of the object is transferred mechanically and then by heating to the thermal energy stores of the object and surface

Question 37

What are the changes in the way energy is stored when bringing water to boil in an electrical kettle

Answer 37

Energy is transferred electrically from the mains to the heating element of the kettle and then by heating to the thermal energy store of the water

Question 38

How is energy transferred mechanically?

Answer 38

a force acting on an object

Question 39

How is energy transferred electrically?

Answer 39

a charge doing work against resistance

Question 40

How is energy transferred by heating?

Answer 40

energy transferred from a hotter object to a colder object

Question 41

How is energy transferred by radiation?

Answer 41

energy transferred by waves