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Physics > CP3 > Flashcards

CP3 Flashcards

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1
Q

What different types of energy stores are there?

A
  1. Chemical energy
  2. Kinetic energy
  3. Thermal energy
  4. Elastic potential energy
  5. Gravitational potential
  6. Nuclear energy
  7. Sound energy
  8. Electrical energy
  9. Light energy
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2
Q

How does energy travel?

A

It travels by being transferred between different stores (e.g. When an electric kettle is used to heat water, energy transferred to the kettle by electricity ends up as a store of thermal energy in the hot water)

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3
Q

What is a system?

A

A set of things being studied (e.g. a kettle, the water in it and its surroundings form a simple system)

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4
Q

What is the law of conservation of energy?

A

The idea that energy can never be created or destroyed, only transferred from one store to another.

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5
Q

What is the unit of measuring energy?

A

Joules (J).

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6
Q

What happens to some energy transferred in a system?

A

Despite energy always being conserved, it is not always transformed into forms of energy that are useful. This is called wasted energy and can be things like thermal energy on the outside of a kettle etc.

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7
Q

How do you represent energy stores and transfers?

A

By using a flow diagram which shows the energy transfers when a car brakes.

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8
Q

What is a Sankey diagram?

A

A diagram showing energy transfers, where the width of each arrow is proportional to the amount of energy it represents.

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9
Q

What are the energy transfers in a process including an object projected up a slope?

A

The objects energy is transferred from the kinetic energy to gravitational potential energy as it slows down and climbs higher.

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10
Q

What are the energy transfers in a process including a moving object hitting an obstacle?

A

The objects energy is transferred from kinetic energy to elastic energy. Some energy remains in the object’s kinetic store as it moves away after the collision.

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11
Q

What are the energy transfers in a process including a vehicle slowing down?

A

The objects energy is transferred from kinetic energy (energy stored in the moving car) to thermal energy (energy stored in the hot brakes)

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12
Q

How can friction between moving parts be reduced?

A

By using lubrication (a lubricant)

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13
Q

What is a lubricant?

A

A substance placed between two moving surfaces to reduce the friction between them

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14
Q

What is wasted energy?

A

Energy that is dissipated and cannot be used for other useful energy transfers.

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15
Q

What are some examples of lubricants?

A

Oil, Grease, Other liquids, Gases etc.

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16
Q

Why is friction bad?

A

As it can create lots of wasted energy such as thermal energy which is wasted energy.

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17
Q

What is efficiency?

A

A way of describing how good a machine is at transferring energy into useful forms.

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18
Q

What number range is given to rate the efficiency of a machine?

A

It is a number between 0-1, the higher the number, the more efficient the machine.

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19
Q

What is the formula for efficiency?

A

Efficiency=useful energy transferred by the device/total energy supplied to the device

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20
Q

What is the formula triangle for efficiency, useful energy and total energy?

A

Useful energy
Efficiency | Total energy

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21
Q

How can the efficiency of an object be increased?

A

For mechanical processes:
1. By reducing friction
2. By making sure all the fuel going into an engine is burned
3. By finding a way of using the energy transferred by heating that would otherwise be wasted

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22
Q

What is insulation?

A

A method of reducing energy transfer often by using insulating materials.

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23
Q

How does insulation help keep our houses warm?

A

It slows down the rate at which energy is transferred out of a house by heating.

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24
Q

What ways can energy be transferred by heating?

A
  1. By conduction
  2. By convection
  3. By radiation
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25
Q

How can energy by transferred by heat in conduction?

A

Vibrations are passed on between particles in a solid.

26
Q

How can energy by transferred by heat in convection?

A

Part of a fluid that is warmer than the rest rises and sets up a convection current.

27
Q

How can energy by transferred by heat in radiation?

A

It is the only way energy can be transferred through a vacuum. Infrared radiation can also pass through gases and some solid materials. Infrared radiation is absorbed and emitted easily by dull, dark surfaces, and is absorbed and emitted poorly by light, shiny surfaces.

28
Q

What does thermal conductivity mean?

A

A measure of how easily energy can pass through a material by heating. A material with low thermal conductivity is a good insulating material.

29
Q

What does the rate of energy transfer through a material by heating depend on?

A
  1. The thickness of the material
  2. The thermal conductivity of the material
  3. The temperature difference across the material
30
Q

What is the effects of the thickness and thermal conductivity of the walls on its rate of cooling?

A

The thicker the walls, the worse the rate of cooling. The less the thermal conductivity, the worse the rate of cooling. The less the temperature difference, the worse the rate of cooling.

31
Q

What are some good thermal insulators?

A

Wood materials.

32
Q

What is gravitational potential energy?

A

Energy that is stored because of an object’s position in a gravitational field.

33
Q

What happens to an object every time it moves upwards?

A

It stores more and more gravitational potential energy.

34
Q

What is the equation for gravitational potential energy?

A

Change in gravitational potential energy (J) = Mass (KG) x Gravitational field strength (N/KG) x Change in vertical height (M)

35
Q

What are the units for the gravitational potential energy equation?

A

GPE = m x g x h (m=mass, g=gravitational field strength, h=change in vertical height

36
Q

What is the formula triangle for GPE, Mass, GFS and Vertical height?

A

GPE
Mass | GFS | Vertical Height

37
Q

What is the value of gravitational field strength on earth?

A

Approximately 10N/kg.

38
Q

What is kinetic energy?

A

Energy that is stored in moving objects.

39
Q

What is the equation for kinetic energy?

A

1/2 x mass(kg) x speedˆ2 (m/sˆ2)

40
Q

What are the units for the kinetic energy equation?

A

KE= 1/2 x m x vˆ2 (KE=kinetic energy, m=mass, v=speed)

41
Q

What is the formula triangle for kinetic energy, Mass and speed?

A

kinetic energy
1/2 | m | vˆ2

42
Q

What are nuclear fuels and what are they useful for?

A

Radioactive metals such as uranium which are used in nuclear power stations to generate electricity. They are very useful for spacecraft, where the mass of the fuel is important.

43
Q

What are fossil fuels?

A

Fuels such as coal, oil and natural gas that were formed from the dead remains of organisms over millions of years.

44
Q

What is most of the UK’s electricity generated from?

A

From fossil fuels such as coal, oil and natural gas.

45
Q

What is a non-renewable energy source?

A

An energy source that will run out because you can’t renew your supply of it.

46
Q

What is oil used for?

A

They are used in most vehicles, aeroplanes and ships as they store a lot of energy and they are easy to store and to use in engines.

47
Q

What is natural gas used for?

A

It is burnt to heat homes or for cooking.

48
Q

How do fossil fuels relate to climate change?

A

Burning fossil fuels release carbon dioxide and other gases. Carbon dioxide emissions contribute to climate change, causing pollution problems.

49
Q

How can you reduce pollution?

A

You can reduce pollution by cutting down the use of fossil fuels. Renewable resources are sustainable ways to reduce pollution.

50
Q

What are renewable resources?

A

An energy resource that will never run out. Most renewable energy resources do not cause pollution or emit carbon dioxide when used to generate electricity because no fuel is burned.

51
Q

What are some advantages and disadvantages to non-renewable energy?

A

Advantages: Cheap to access, Quickly obtainable
Disadvantages: Harmful for the environment, Non-renewable

52
Q

Why is nuclear energy not a suitable solution for reducing climate change?

A

Despite it not emitting any carbon dioxide or other gases, the waste they produce is radioactive and it is expensive to dispose of safely. Also, if a major radioactive accident occurs, it could have very serious consequences.

53
Q

What are some advantages and disadvantages to renewable energy?

A

Advantages: Less climate change, Reliable and sustainable
Disadvantages: Expensive, Requires a lot of space

54
Q

What are some types of renewable resources?

A
  1. Solar cells
  2. Hydroelectricity
  3. Wind turbines
  4. Bio-fuels
55
Q

How do Solar Cells work?

A

They convert solar energy directly into electrical energy, in solar farms or on house roof-tops.

56
Q

How does Hydroelectricity work?

A

It is generated by falling water in places where water can be trapped in high reservoirs, which spins a generator that generates electricity.

57
Q

How do Wind Turbines work?

A

They can be used to generate electricity as long as the wind speed is not too slow or fast. The wind makes the turbines spin which spins a generator that generates electricity.

58
Q

How does Tidal Power work?

A

It can generate electricity when turbines in a huge barrier (dam) across a river estuary turn as the tides flow in and out.

59
Q

How do Bio-fuels work?

A

They can be used in the same way as fossil fuels but they are made from animal wastes or from plants instead. They are carbon neutral as when they burn, they release the same amount of carbon dioxide that they took from the atmosphere when the plants grew.

60
Q

Why can’t we only use renewable resources at this time?

A

Because most are not available all the time. It takes a lot of land and resources to produce them as well.

61
Q

What is the general trend of renewable and non-renewable resources in recent times?

A

The trend for non-renewable is that less coal and oil is being used than before while more natural gas is being used now. The trend for renewable resources is that all forms of renewable resources are being more widely used than they used to be.

Physics (13 decks)

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