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Physics > Topic 3: Conservation Of Energy > Flashcards

Topic 3: Conservation Of Energy Flashcards

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1
Q

What are the different energy stores?

A 
Chemical energy 
Kinetic energy
Gravitational potential energy
Elastic potential energy/ strain energy
Thermal energy
Nuclear/atomic energy
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2
Q

Examples of chemical energy:

A

Energy stores in food, fuel and batteries.

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3
Q

Examples of kinetic energy:

A

Energy stored in moving objects.

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4
Q

Examples of nuclear energy:

A

Energy stored inside atoms.

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5
Q

Examples of gravitational energy:

A

Stored in objects in a high position.

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6
Q

Examples of elastics/stretch energy:

A

Squashed, twisted or stretched materials

E,g
Elastic band
Elastic
Spring

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7
Q

Examples of thermal energy:

A

Stored in hot objects.

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8
Q

What is a system (in physics)?

A

Describes something in which we are studying change.

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9
Q

What is the law of conservation of energy?

A

Energy cannot be created or destroyed just transferred from one source into another.

This means that the total energy transferred by a system is the same as the energy out into the system.

Units for measuring energy is joules (J)

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10
Q

How can e ergo transfers be unuseful?

A

Although it is always conserved it is not always transferred into useful energy transfers. A lot of energy is normally wasted as thermal energy.

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11
Q

What does dissapitated mean?

A

It means when energy (spreads out) and cannot be used for other energy transfers - it’s wasted.

This normally happens when energy is transferred to surrounding BY heating.

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12
Q

How does friction lead to energy dissipated energy?

A

Machines waste energy when they get hot. Whenever two moving parts touch each other, friction causes them to heat up. THE THERMAL ENERGY STORED IN THE HOT MACHINES CAN BE TRANSFERRED BU HEATING, which dissipates the energy.

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13
Q

What does efficiency mean?

A

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

The efficiency of a machine is given a number between 0-1. 1 being very efficient.

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14
Q

What equation can be used to work out efficiency?

A

Efficiency = useful energy/total energy

There are no units.

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15
Q

Why can’t efficiency be a number over 1.

A

It a,ways has to be a number between 0 and 1. If it goes over it means you’ve made more energy which is impossible.

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16
Q

How can you increase efficiency?

A

By reducing the amount of wasted energy it can increase efficiency in a device or process.

E.g. for a mechanical process such as engines it may mean reducing friction so less energy is given out by heating. Lubricant or oil could do this.

Or finding a way of using the energy transferred by heating so it’s not wasted.

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17
Q

What does insulation mean and what does it do?

A

Insulation slows down the rate at which energy is transferred out of and ‘object’ by heating such as a house.

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18
Q

What are the three ways heat can be transferred?

A
  • Conduction
  • convection
  • radiation
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19
Q

How does conduction transfer heat?

A

In conduction vibrations are passed on between particles in a solid. Metals are good thermal conductors (because they are solid).

Particles near the war end vibrate. Particles collide and transfer energy. Energy transferred to surroundings.

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20
Q

How does convection transfer energy by heating?

A

In convection part of a fluid that is warmer than the rest rises so it becomes less dense. Water can’t escape so moves along surface. Water is cooled becomes more dense and so sinks. Water moves along botttom of beaker

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21
Q

How does radiation transfer energy by heating?

A

Radiation is the only way energy can be transferred in a vacuum. Infrared radiation can a,so pass through gases and some solids. It is given off form warm objects as waves.

22
Q

Why is radiation u I que and important?

A

Because it doesn’t need particles. This means he sun uses radiation to heat the earth.

23
Q

Why to metals transfer heat better?

A

Because they have free flowing electrons.

24
Q

What happens to an object of is has low thermal conductivity?

A

This means the energy is not transferred through the very easily by heating.

25
Q

Why are materials that contain air good insulators?

A

Because air has a very low thermal conductivity. When air is trapped it cannot form convection currents and so does not transfer much energy.

26
Q

What does the rate of energy when transferred through materials by heating depend on?

A

The thickness of the material and its thermal conductivity and on the temperature difference across it. The rate of energy transfer is reduced by increasing thickness, decreasing thermal conductivity and decreasing temperature difference.

27
Q

How is a vacuum flask adapted to store hot or cold liquids?

A
  • plastic stopper
  • glass walls with silver coating on both sides. (Reflect heat back)
  • vacuum between walls (can transfer energy through convection)
  • plastic spacer
28
Q

How is gravitation potential energy stored?

A

Stored because of an objects position in a gravitational field.
Any object stored above surface of earth contains a stores of GP energy. The higher it is the bigger the store.

29
Q

What does the amount of GPE in an object depend on?

A

The mass of the object. The strength of gravity and how far the is movies upwards.

30
Q

What is the equation for GPE?

A

Change in GPE= mass x gravitational field strength x change in vertical height

31
Q

What is the equation for kinetic energy?

A

Kinetic energy = 1/2 x mass x speed spqaured

32
Q

Name one way in which nuclear fuels are important?

A

They store a lot of energy in a small piece of material. Makes them useful for spacecrafts where the mass of the fuel is important. (e.g uranium)

33
Q

How is electricity generated in the UK?

A

using nuclear fuels or fossil fuels, coal, oil and natural gas.

34
Q

What does non renewable energy resources mean.

A

They will run out one day. We have a limited supply of them.

35
Q

What is oil used for?

A

Petrol and diesel are made from oil. They are used in most vehicles, aeroplanes and ships because they store a lot of energy and are easy to store and use in engines.

36
Q

What is natural gas used for?

A

Burn to heat homes or for cooking (stove).

37
Q

Why are burning fossil shells bad for the environment?

A

They release carbon dioxide and other gases (such as soulful dioxide that causes acid rain.) carbon dioxide emissions contribute to climate change as it is a green house gas.

38
Q

Why is burning natural gas better than burning coal?

A

Because it causes less pollution. Natural gas power stations also emit less carbon dioxide than other fossil fuelled power stations but produce the same amount of electricity.

39
Q

Why are nuclear power stations better for environment than fossils fuelled ones?

A

They don’t produce carbon dioxide or any other harmful gases that can cause harm to the environment.

They are also cheaper to run during their life.

40
Q

What are the drawbacks of nuclear power stations?

A
  • They produce radioactive waste and some of it will stay radioactive for millions of years.
  • This is expensive to dispose of safely.
  • They are also very expensive to decommission safely at the end of the power stations life. (More expensive than a fossil fuelled one)
41
Q

Wha happens if there is a nuclear power station leak.

A

Radioactive materials are released into the atmosphere. It can also pollute the sea and spread.

42
Q

What are renewable energy resources?

A

Resources that will not run out. Most of them do not cause pollution or emit carbon dioxide when used to generate electricity.

43
Q

What are solar cells and what do they do?

A

They convert solar energy directly into electrical energy. In ‘solar farms’ or on house roof tops. It can also be used to heat watering homes. However it is not available all the time.

44
Q

What is hydroelectricity and how is it used?

A

Generated by falling water falling into places where water can be trapped in high reservoirs. Available all the time (as long as reservoir our doesn’t dry up). A hydroelectric power station can be started and stopped very quickly unlike nuclear and fossil fuelled ones.

45
Q

What are wind turbines and how are they

used?

A

Can be used to generate electricity as long as wind speed is not too slow or fast. However slot of them are needed to produce the same amount of energy as a fossil fuelled power station and they ruin the landscape.

46
Q

What is total power and how is it used?

A

An generate electricity when turbines in a huge barrage (dam) across an estuary turn as tide flows in and out. Not available all the time but is available at predictable times. Not many places in UK that are suitable for a barrage and can affect birds and wildlife that live and feed on tidal mudflats.

Can also be places in water currents in the sea to generate electricity.

47
Q

What are bio fuels?

A

Can be used in the same way as fossil fuels. Made from animal waster from plants, waste wood. Some rips are also grown especially for this.

48
Q

Why are bio fuels carbon neutral?

A

Because when they burn they release the same amount of carbon dioxide that they took from the atmosphere when the plant or animal grew.

49
Q

What is the argument against carbon fuels begin carbon neutral?

A

Energy is also needed to grow and harvest the crops to turn them into a fuel so most bio fuels can also be described as not being carbon neutral.

50
Q

Why can we not only use renewable energy resources?

A

Because of them are not available all the time. It also takes a lot of land to obtain the energy such as solar farms or wind turbine farms.

Physics (11 decks)

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