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AQA GCSE Physics > Energy > Flashcards

Flashcards in Energy Deck (100)
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1

Name the energy stores:

-Thermal energy stores
-Kinetic energy stores
-Gravitational energy stores
-Elastic potential energy stores
-Chemical energy stores
-Magnetic (spectrum) energy stores
-Electrostatic energy stores
-Nuclear energy stores

2

What are the four ways in which energy is transferred?

-Mechanically (force doing work)
-Electrically (work done by moving charges)
-Heating
-Radiation (waves)

3

What is a system?

a collection of particles

4

What happens when a system changes?

Energy is transferred. It is transferred into or away from the system, between different objects in the system or between different types of energy stores.

5

What are closed systems?

Closed systems are systems where neither matter nor energy can enter or leave it. The net change in the total energy of a closed system is always zero.

6

How is energy transferred in a kettle?

electrically to the thermal energy store of the kettle's heating element which then transfers by heating to the water's thermal energy store.

7

What does work done mean?

Energy transferred

8

How can work be done?

Work can be done when current flows (energy is transferred against resistance in a circuit) or by a force moving an object.

9

What type of energy is stored for anything that is moving?

Kinetic

10

How is energy transferred to and from the kinetic energy store?

It is transferred to the kinetic energy store when an object gains speed and is transferred away from this store when an object slows down.

11

What increases the amount of energy in the kinetic energy store?

The larger the mass and the faster the speed of the object

12

What is the equation for calculating kinetic energy?

Kinetic energy (j) = 1/2 x Mass(kg) x (speed x speed)(m/s)

KE = 0.5 x mv^2

13

What energy do raised objects store?

gravitational potential energy

14

What does the amount of energy transferred to the gravitational potential energy store depend on?

It depends on the object's mass, height and the strength of the gravitational field the object is in. The higher the object is lifted, the more energy that is transferred

15

What is the equation for finding the change in energy of an object's gravitational potential energy stores for a change in height?

G.P.E (J) = Mass(kg) x Height(m) x gravitational field strength (N/kg)

G.P.E = mgh

16

What energy transfer do falling objects undergo?

Energy from the object's gravitational potential energy store is transferred to its kinetic energy store

17

What is the relationship between the amount of energy in the G.P.E store and the kinetic energy store for a falling object with no air resistance?

Energy lost from the G.P.E store = Energy gained in the kinetic energy store

18

What effect does air resistance have on the energy transfer of a falling object?

It causes some energy to also be transferred to other energy stores

19

What effects can squashing and stretching have on the transfer of energy?

can transfer energy to its elastic potential energy store

20

What is the equation for working out energy in the elastic potential energy store so long as the limit of proportionality has not been exceeded?

Elastic potential energy(J) = 0.5 x spring constant (N/m) x extension^2 (m)

EPE = 0.5 x k x e^2 or EPE = 0.5 x F x e

21

Why do different materials have different specific heat capacities?

Because more energy needs to be transferred to the thermal energy stores of some materials to increase their temperature than others.

22

What happens in materials that need to gain lots of energy in their thermal energy stores to warm up?

These types of materials also transfer loads of energy when they cool down again. They can "store" a lot of energy.

23

What is specific heat capacity?

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

24

What is the formula with specific heat capacity?

energy transferred by heating(J) = Mass(kg) x specific heat capacity (J/kg degrees. Celsius ) x temperature change
E = mcΔØ

25

What is the law of the conservation of energy?

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

26

What is dissipated energy?

Dissipated energy is the energy that is not usefully transferred into the store that you want it to go. It is sometimes called "wasted energy"

27

How does energy transfer wastefully in a closed system?

Energy transfers occur within the system to "waste" stores but no energy has left the system so the net change in energy is zero

28

What is power?

Power is the rate of energy transfer.

29

What is power measured in?

Power is measured in Watts. One watt = 1 joule of energy transferred per second

30

What are the equations for calculating power?

Power(W) = Energy transferred (J) /Time (s)
P = E/t

Power(W) = Work done(J) / Time (s)

W = J/s

31

What is a powerful machine?

A powerful machine is one which transfers a lot of energy in a short space of time

32

Where does energy transferred to an object by heating go?

It goes to the thermal energy store of an object. The energy is shared across the kinetic energy stores of the particles in the object.

33

What is conduction?

the particles in the part of the object that is being heated gain energy and vibrate faster. The particles collide and this causes energy to be transferred between particle's kinetic energy stores

34

What is thermal conductivity?

Thermal Conductivity is a measure of how quickly energy is transferred through a material using conduction. Materials with high thermal conductivity transfer energy between particles quickly.

35

What is convection?

Convection is where energetic particles in a liquid or gas move away from hotter to cooler regions. (When a region of a liquid or gas is heated , the particles move faster and the space between the particles increases (less dense). The warmer and less dense region will rise above the denser and cooler regions)

36

How is energy transferred between a radiator and nearby air particles?

The air particles collide with the radiator and energy is transferred through conduction

37

What is a frictional force?

A frictional force is a force that goes against something when its moving. This causes energy in the system to be dissipated.

38

How can friction be reduced between two objects?

Using lubricants

39

How can you prevent energy loss through heating in a house/building?

-By having thick walls with low thermal conductivity (this slows rate of energy transfer)
-Using thermal insulation

40

What are some thermal insulation methods?

-Loft Insulation
-Cavity Walls
-Double-Glazed Windows
-Draught excluders

41

How do cavity walls and double-glazed windows work?

They both have an inner and outer layer (ie. wall or window) with an air gap in between. This reduces the amount of energy transferred by conduction through the windows or walls. Foam can be put in the cavity wall air gap to also reduce energy transfer by conduction

42

What does loft insulation do?

Loft insulation reduces convection currents being created in lofts

43

What do draught excluders do?

They are put around doors and windows to reduce energy transfer by conduction

44

What is waste energy?

The input energy that is transferred to a useless energy store

45

How can you improve the efficiency of energy transfers?

-Insulation
-Lubrication
-Streamlining

46

What is the equation for calculating the efficiency of an energy transfer?

Efficiency = Useful output energy transfer/total input energy transfer

47

How do you calculate the efficiency of an energy transfer if you know the power input and output?

Efficiency = Useful power output/total power input

48

What are the features of non-renewable energy resources?

-They will all run out one day
-They do damage to the environment
-They provide most of our energy
-They are fossil fuels and nuclear fuel (uranium and plutonium)

49

What are the three main fossil fuels?

-Coal
-Oil
-Natural Gas

50

What are the features of renewable energy resources?

-They will never run out (can be renewed)
-Damage the environment but less harmfully
-Don't provide as much energy
-Less reliable(weather dependent)

51

What are the renewable energy resources?

-The Sun - heating panel,solar panel, solar tower
-Wind
-Water waves
-Hydro-electricity
-Bio-fuel, e.g. methane and ethanol
-Tides
-Geothermal

52

What are the two common things that energy resources are used for?

-Transport:
petrol and diesel powered vehicles (created from oil),
coal is used in steam powered trains, some cars run on bio-fuels
-Heating:
natural gas to heat water for radiators, coal for fireplaces, electric heaters, geothermal heat pumps, solar water heaters

53

What are the advantages of wind turbines?

-No fuel costs
-Minimal maintenance and running costs
-No permanent damage to landscape
-No pollution

54

What are the disadvantages of wind turbines?

-Very noisy
-Spoil landscape
-Have to be put in windy places
-Produce energy 70-85% of the time as they are wind reliant
-1500 of them=one coal-fired power station
-High initial cost
-Can't increase power output

55

What are the advantages of solar cells?

-Good source for low power objects (e.g. watches, calculators, road signs etc.)
-No pollution
-Reliable in sunny places
-Cost effective even in Britain
-Energy is free
-Low maintenance cost

56

What are the disadvantages of solar cells?

-Generate electricity on a relatively small scale
-Can't increase power output
-Expensive to make

57

What are the advantages of Geothermal power?

-Reliable
-Free energy
-Little damage to environment
-Can generate electricity or heat buildings directly

58

What are the disadvantages of Geothermal power?

-Aren't many suitable locations for Geothermal power plants (in volcanic areas or where hot rocks lie near the Earth's surface)
-Cost of building a power plant is high compared to the amount of energy it produces

59

Where does most of our electricity come from?

Nuclear power or fossil fuels

60

Are we using more or less energy now?

The electricity use in the UK rapidly increased in the 20th Century but has been decreasing slowly throughout the 21st century as electrical appliances become more efficient and we are more aware of it.

61

Why do more people want to use renewable energy resources?

They want to use more renewable energy resources as we are aware of the limited supply of nuclear energy and fossil fuels and the negative impact from generating electricity from these.

62

What are some of the problems the Government is facing in trying to increase the amount of energy produced by renewable resources?

-The cost of switching to renewable resources is high
-There is much debate over the location of the renewable energy methods
-Research into the new renewable ideas is expensive
-Renewable energy is far less reliable
-Hybrid and electric cars are generally more expensive

63

What are internal energy stores?

The sum of the total kinetic energy and potential energy of an object

64

What are the mechanical waves/ energy stores?

Gravitational potential, elastic potential, kinetic and sound

65

Where is chemical energy located?

Between the bonds in the atoms and molecules

66

Where is nuclear energy located?

Between the protons and neutrons in the nucleus

67

What is the equation for calculating the energy transferred when a current flows?

Work done = current(A) x potential difference(V) x time(s)
E = IVt

68

How strong of a force is required to lift an object at a constant velocity?

A force which is equal and opposite to that of the gravitational force on the object

69

Equation for working out energy transferred by forces

W = F x s(distance)

70

Name all the parts of the EM spectrum from longest to shortest

Radio Waves - Micro Waves - Infrared - Visible Light - Ultra violet - X-rays - Gamma Rays

71

How does lubricant improve efficiency?

Lubricant reduces the amount of energy wasted by two surfaces that are rubbing together through friction. Lubricant separates the two surfaces to reduce friction which would increases the internal energy of the surroundings

72

What do insulating materials have?

Low thermal conductivity (reduces power over surface)

73

What is significant, in terms of structure that makes some materials have a high thermal conductivity (conduction)?

They have a rigid lattice structure of ions with delocalised electrons (increased collisions and energy transfers)

74

What is significant, in terms of structure that makes some materials have a low thermal conductivity ?

Have no delocalised conduction electrons and no regular lattice (amorphic-irregular-different bond lengths)

75

What state of matter is a good insulator?

Gases as they have "no bonds" between particles.

76

What are the three ways to decrease thermal conductivity?

-increasing thickness of material
-decreasing the surface area
-decreasing the temperature gradient

77

What is the total process of generating electricity which all resources can apply to in places?

Resource-Furnace/reactor-boiler-turbine-generator

78

How is energy distributed?

Through the National Grid

79

What is the national grid?

A network of power stations, transformers, power lines (transmission cables) and consumers

80

What does a step-up transformer do?

Increase the P.D. of an electric charge and decrease the current. The low current means less energy is dissipated to internal energy stores of surroundings

81

What does a step-down transformer do?

Decrease the P.D. of the received charge and increases the current to required levels for consumers

82

What are the four mechanisms for thermal energy transfer?

Conduction
Convection
Evaporation
Radiation

83

What is convection?

1)Localised decrease of density due to increased particle movement
2) This region of fluid "floats" and the energy is transferred to surroundings of lower temperature
3)Density increases due to decreased particle motion so region sinks

84

What is evaporation?

Surface particles in a body (solid or liquid) gain sufficient extra kinetic energy to escape from the bonds holding them in the surface
Overall average kinetic energy of body is reduced

85

What is radiation as a thermal energy transfer mechanism?

A transfer of energy from a source of electromagnetic waves

86

What is the main source of radiation from humans which transfers energy?

Infrared

87

What is a perfect black body?

A body which emits the most intense (peak) wavelength. Absorbs all radiation that hits it, does not transmit or reflect any radiation either.

88

All objects emit infrared radiation, what is the rate of emission dependent upon?

The temperature of the body (higher temperature = faster rate of emission)

89

What does a temperature increase in a body result in terms of radiation intensity?

The intensity of radiation emitted increases at all wavelengths

90

How can infrared radiation be detected?

Using an infrared camera or sensor, by warmth on the skin, by a rise in temperature (particularly with a blackened thermometer)

91

What colour is an object likely to appear when it is hotter (radiation related)?

Blue/white

92

What colour is an object likely to appear when it is cooler (radiation related)?

Redder

93

What is the basic principle of emission and absorption of infrared radiation?

All objects do both whatever their temperature

94

What does it mean in regards to infrared radiation processes when an object is at a constant temperature?

The object is absorbing and emitting the radiation at the same rate

95

What are the greenhouse gases and what do they do (infrared radiation)?

Molecules of water vapour, methane and carbon dioxide gas- absorb infrared radiation emitted by the ground which causes temperature of atmosphere to rise. They emit the same wavelength as emitted by earth's surface

96

What is the difference in radiation wavelengths emitted by the sun and the Earth?

Earth's radiation has longer wavelength than that which it absorbs from the Sun

97

Name two ways which fossil-fuelled power stations can be less harmful to the environment ie. releasing greenhouse gases and releasing sulfur dioxide (acid rain)

Use carbon capture and storage and remove the sulfur

98

How can excess energy generated be stored?

Through pumping

99

What propety do materials which contain trapped pockets of air tend to have?

very low thermal conductivity

100

Describe what is meant by energy dissipation:

The transfer of energy to a store from which it cannot be retrieved