Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ZZ Phys 1 > energy > Flashcards

energy Flashcards

1
Q

Define a system

A
  • an object or group of objects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What happens when a system changes?

A
  • energy is transferred
  • this can either be into or away from a system, between different objects or between different types of energy stores within a system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens when energy is transferred to an object?

A
  • the energy is stored in one of the object’s energy stores
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

List the energy stores

A
  • kinetic
  • thermal
  • chemical
  • gravitational potential
  • elastic potential
  • electrostatic
  • magnetic
  • nuclear
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a kinetic energy store?

A
  • energy stored in a moving object
  • depends on object’s mass and speed - greater the mass and faster, more energy
  • energy is transferred to this store when an object speeds up and transferred away when slows down
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a thermal energy store?

A
  • all objects have thermal energy stores
  • the higher the temperature the more thermal energy it stores
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a chemical energy store?

A
  • energy stored in substances that can release the energy by a chemical reaction
  • this includes food, fuels and even our muscles
    e.g. chemical energy stored in muscles is transferred to kinetic energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a gravitational potential energy store?

A
  • energy stored in objects with mass and are inside a gravitational field
  • higher the object lifted, more energy transferred to this store
  • amount of energy in a GPE store depends on object’s mass, height & strength of gravitational field
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is an elastic potential energy store?

A
  • energy stored in stretched or compressed objects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is an electrostatic potential energy store?

A
  • energy stored in objects with an electric charge interacting with another electric charge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a magnetic energy store?

A
  • energy stored in magnets that are interacting with other magnetic material
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a nuclear energy store?

A
  • energy stored in atomic nuclei released in nuclear reactions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a closed system?

A
  • a system where neither matter nor energy can enter or leave
  • therefore the net change in total energy is always zero
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How can we transfer energy?

A
  • mechanically
  • doing work by exerting a force on an object and moving it
  • electrically
  • a current moving through a potential difference can do work
  • heating
  • energy can be transferred from a hotter object to a colder object and through radiation when energy is transferred by waves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the energy changes when an object is falling

A
  • when something is dropped from a height, it’s accelerated by gravity
  • as it falls, energy from gravitational potential energy store is transferred to its kinetic energy store
  • air resistance acts against all falling objects
  • causes energy to be transferred to other energy stores
    e.g. thermal energy stores of the object and surroundings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the energy changes when an object is projected upwards

A
  • the chemical energy store in the person’s muscle decreases
  • energy is transferred to the kinetic energy stores of the object.
  • as its altitude increases, the kinetic energy stores decrease
  • kinetic energy is transferred to gravitational potential energy
  • so the gravitational potential energy stores increase
  • some of the kinetic energy is dissipated as thermal energy to the surroundings due to air resistance acting on the object
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe the energy changes when a moving object hits an obstacle

A
  • the kinetic energy decreases as it is transferred to the thermal energy stores of the obstacle due to friction
  • the thermal energy stores of the obstacle increase
  • leading to the energy being dissipated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe the energy changes when a vehicle slows down

A
  • kinetic energy is transferred to the thermal energy store in the brake pads
  • the energy is dissipated as kinetic energy stores of the car decrease and thermal energy stores in the breaks increase due to work being done by friction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe the energy changes when bringing water to a boil in a kettle

A
  • energy is transferred from the electrostatic stores in the wires to thermal energy in the heating element
  • thermal energy is transferred to the thermal energy stores in the water, causing it to boil
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe the energy changes when a ball rolls and hits the wall

A
  • system is the moving ball
  • when it hits the wall some of the kinetic energy is transferred as sound
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Why is it impossible to be 100% efficient?

A
  • some energy is always dissipated when an energy transfer takes place
  • the energy is wasted/stored in a way that is not useful
  • dissipation is usually by energy transfer to the thermal energy stores of the surroundings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Why is total energy in a closed system is always the same (law of conservation)?

A
  • no energy can enter or leave the closed system
  • since energy cannot be created or destroyed, the total energy is always the same
    e.g. cold spoon in an insulated flask: spoon warms up, soup cools down, net change in energy is 0
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the condition for using the elastic potential equation?

A
  • that the limit of proportionality has not been exceeded
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the properties of energy?

A
  • it can be transferred usefully, stored or dissipated
  • but cannot be created or destroyed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Define power

A
  • the rate at which energy is transferred or the rate at which work is done
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is an energy transfer of 1 joule per second equal to?

A
  • a power of 1 watt
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Give an example that illustrates the definition of power

A
  • a powerful machine does not necessarily exert a strong force – a powerful machine is one that transfers a lot of energy in a short space of time
    e.g. two identical cars that are racing on the same distance along a straight race track to a finish line - the car with the more powerful engine will reach the finish line faster because it will transfer the same amount of energy, but over less time
  • another example is two electric motors both lifting the same weight through the same height, but the one with the greater power rating lifts it faster as energy is transferred at a faster rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Name the main factors that affect the rate of energy transfer

A
  • thermal conductivity and thickness of the walls
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How does conduction work?

A
  • energy transferred to an object by heating is transferred to the thermal store of the object
  • energy is shared across the kinetic energy stores of the particles in the object
  • the particles in the part of the object being heated vibrate more and collide with each other
  • these collisions cause energy to be transferred between particles’ kinetic energy stores
  • this process continues throughout the object until the energy is transferred tot he other side of the object
  • it is then usually transferred to the thermal energy store of the surroundings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Give an example of conduction

A
  • energy transferred through a metal pan handle
  • energy is transferred by induction trough the pan to the water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Define conduction

A
  • process where vibrating particles transfer energy to neighbouring particles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

How does conduction work?

A
  • energy transferred to an object by heating is transferred to the thermal store of the object
  • energy is shared across the kinetic energy stores of the particles in the object
  • the particles in the part of the object being heated vibrate more and collide with each other
  • these collisions cause energy to be transferred between particles’ kinetic energy stores
  • this process continues throughout the object until the energy is transferred tot he other side of the object
  • it is then usually transferred to the thermal energy store of the surroundings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Define convection

A
  • where energetic particles move away from hotter to cooler regions
  • only occurs in gases and liquids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

How does convection work?

A
  • energy is transferred by heating to the thermal store of the liquid or gas
  • energy is shared across the kinetic energy stores of the gas or liquid’s particles
  • particles able to move so when you heat a region of gas or liquid the particles move faster and the space between individual particles increase - causes density of reason being heated to decrease
  • because liquids and gases can flow, the warmer and less dense region will rise - if there is a constant heat source, convection current can be created
35
Q

Explain how radiators create convection currents

A
  • energy is transferred from the radiator to the nearby air particles by conduction (the air particles collide with the radiator surface).
  • the air by the radiator becomes warmer and less dense (as the particles move quicker).
  • this warm air rises and is replaced by cooler air - the cooler air is then heated by the radiator.
  • at the same time, the previously heated air transfers energy to the surroundings (e.g. the walls and contents of the room) - it cools, becomes denser and sinks.
  • this cycle repeats, causing a flow of air to circulate around the room - this is a convection current.
36
Q

Define thermal conductivity

A
  • measure of how quickly energy is transferred through a material via conduction
  • materials with a high thermal conductive transfer energy between their particles quickly
37
Q

Describe the relationship between the rate of energy transfer and thermal conductivity

A
  • the higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material; i.e. the lower the thermal conductivity, the more well-insulated a house is
38
Q

What feature do most houses have in terms of thermal conductivity?

A
  • most houses have an internal and external wall with a cavity in between, which forms a relatively high thermal conductivity
39
Q

How can you reduce unwanted energy transfer via thermal conductivity?

A
  • cavity wall insulation
  • double-glazed windows
  • loft insulation
  • draught excluders
40
Q

How do cavity walls / cavity wall insulation reduce unwanted energy transfer?

A
  • made up of an inner and outer wall with an air gap in the middle
  • air gap reduces amount of energy transferred by conduction through walls (low thermal conductivity)
  • when there’s insulation (air gapped filled with foam), reduce energy transfer by convection
  • this reduces cost of heating because less energy is wasted
41
Q

How does loft insulation reduce unwanted energy transfer?

A
  • can be laid out across the loft floor and ceiling
  • fibreglass wool is often used which is a good insulator as it has pockets of trapped air (lower thermal conductivity due to layer of insulating air between two layers of glass)
  • reduces energy loss by conduction and also prevents convection currents from being created
42
Q

How do double glazed windows reduce unwanted energy transfer?

A
  • work in the same way as cavity walls - have an air gap between two sheets of glass to prevent energy transfer by conduction through windows
    e.g. fibreglass has air gaps that give it a low thermal conductivity
43
Q

How do draught excluders reduce unwanted energy transfer?

A
  • around doors and windows
  • can stop draughts blowing in and out, reducing energy transfer by convection
44
Q

Describe the relationship between the rate of energy transfer and thickness of walls

A
  • the thicker the walls, the slower the rate of unwanted thermal energy transfer
    i.e. an ideal house has walls with a low thermal conductivity and very thick walls
45
Q

What are lubricants?

A
  • substances (usually liquids) that coat objects and flow between the moving parts
46
Q

How do lubricants work to reduce unwanted energy transfers?

A
  • whenever something moves, frictional forces always act on it that cause energy to be dissipated and transferred to thermal energy stores of the surroundings
  • lubricants reduce friction (they can flow easily between objects and coat them) between forces when they move so that less energy (heat) is transferred to the surroundings
47
Q

How do you reduce friction?

A
  • lubricants
48
Q

How do you reduce air resistance

A
  • streamline
49
Q

Define efficiency

A
  • the ratio of the useful work done by a machine, engine, device to the energy supplied to it
50
Q

What is a useful device?

A
  • devices that transfer energy from one energy store to a useful energy store
51
Q

What is the exception to no devices being 100% efficient?

A
  • electric heaters, because all the energy is transferred to the useful thermal energy stores
52
Q

How can efficiency of a device be increased?

A
  • reducing waste output - by lubrication or insulation
  • recycling waste output - absorbing thermal waste and recycling as input energy
53
Q

Name the fossil fuels

A
  • coal
  • oil
  • gas
54
Q

What is coal used for?

A
  • heating - fireplaces
  • electricity generation
  • transport - steam trains
55
Q

What is oil used for?

A
  • transport - petrol + diesel in vehicles
  • electricity
56
Q

What is gas used for?

A
  • heating - gas is used to heat water which is then pumped into radiation
  • electricity generation
57
Q

List renewable energy resources

A
  • nuclear
  • biofuel
  • wind
  • hydroelectricity
  • tidal
  • geothermal
  • solar
  • waves
58
Q

Define renewable energy resource

A
  • an energy resource that is being replenished as it is used up so it will never run out
59
Q

Define non-renewable energy resource

A
  • an energy resource that is not being replenished as quickly as it is used up, so will run out one day
60
Q

What is the environmental impact of fossil fuel use?

A
  • involve destroying landscapes
  • release greenhouse gases
61
Q

Why is non-renewable energy used for more large-scale energy supplies?

A
  • due to the large energy output per kg of fuel
62
Q

Why has renewable energy become more important?

A
  • due to the finite lifetime of fossil fuels, so their development has become more important
63
Q

What are the advantages of renewable energy?

A
  • they will never run out
  • they don’t produce greenhouse gases because they don’t release CO₂
  • they don’t create radioactive waste products
64
Q

What are the disadvantages of renewable energy?

A
  • they still generate pollution
  • low-efficiency levels
  • can be unreliable
  • generally expensive
65
Q

What fuels can be used for nuclear power?

A
  • uranium (or plutonium)
66
Q

What are the advantages of nuclear fuel?

A
  • they don’t produce greenhouse gases because they don’t release CO₂
  • more energy rich than fossil fuels
  • relatively cheap
67
Q

What are the disadvantages of nuclear fuel?

A
  • toxic nuclear waste to dispose of
    a fire or explosion at a nuclear power station would cause significant environmental damage
  • overall cost of nuclear power is high due to cost of power plant and final decommissioning
68
Q

What are the advantages of hydroelectric power?

A
  • no pollution
  • no problems with reliability except in times of drought
  • no fuel costs and minimal running costs
  • useful way to regenerate electricity on a small scale in remote areas
69
Q

What are the disadvantages of hydroelectric power?

A
  • flooding of the valley - rotting vegetation releases methane and carbon dioxide)
  • can damage habitats as it involves damming rivers
  • reservoirs look unsightly when dried up
70
Q

What are the advantages of geothermal energy?

A
  • reliable with very few environmental problems
71
Q

What are the disadvantages of geothermal energy?

A
  • only certain places can access enough heat (only possible in volcanic areas where hot rocks are near the surface)
  • the source of most of the energy is the slow decay of various radioactive elements
  • cost of building a power plant is high compared to amount of energy it produces
72
Q

What are the advantages of wind power?

A
  • no pollution (expect for manufacture
  • no fuel costs and minimal running costs
  • no permanent damage to the landscape
73
Q

What are the disadvantages of wind power?

A
  • it isn’t always windy (impossible to increase supply when there’s extra demand)
  • it’s expensive to build
  • eyesore - ruins scenery
  • noisy - annoying for people who live nearby
74
Q

What are the advantages of solar power?

A
  • no pollution
  • in sunny countries it’s reliable
  • energy is free - running costs almost nil
75
Q

What are the disadvantages of solar power?

A
  • it isn’t always sunny, only works in daytime (can’t increase the power output when there is extra demand)
  • expensive to build
  • generate electricity on a small scale
76
Q

What are the advantages of wave energy?

A
  • no pollution
  • no fuel costs and minimal running costs
  • useful on small islands
77
Q

What are the disadvantages of wave energy?

A
  • waves vary; not a consistent source of energy - fairly unreliable
  • they can only be built in certain places
  • initial costs are high
  • never likely to provide energy on a large scale
  • disturbs seabed and habitats of marine animals - spoiling view and being a hazard to boats
78
Q

What are the advantages of tidal energy?

A
  • no pollution
  • pretty reliable (tides twice a day without fail and near predicted height
  • no fuel costs and minimal running costs
79
Q

What are the disadvantages of tidal energy?

A
  • only two tides a day (produced by the gravitational pull of the Sun and Moon)
  • height of tide is variable, lower tides provides less energy - don’t always work when water is same level either side of barrage
  • prevents free access by boats
  • spoils view
  • alerts habitat of wildlife, e.g. wading birds & sea creatures who live in the sand
  • initial costs are moderately high
  • can only be used in some of the most suitable estuaries
80
Q

What are the advantages of using biomass?

A
  • carbon neutral (only if you keep growing plants at the rate you’re burning things
  • fairly reliably - crops take relatively short time to grow & different crops can be grown all year round
81
Q

What are the disadvantages of using biomass?

A
  • cannot respond to immediate energy demands
  • cost to refine bio-fuels so they are suitable for use is very high
  • may not be enough space or water to meet demands for crops grown for food
  • large areas of forests been cleared to make room to grow bio-fuels - destruction of habitats + decay and burning of vegetation increases greenhouse gas emission
82
Q

Describe the patterns and trends of energy use

A
  • during industrial revolution, fossil fuels became an important source of energy as it was easy to mine, and provided a lot of energy
  • only recently has renewable energy become more suitable – technology has had to develop a lot since industrial revolution to be able to harness such energy sources efficiently
  • it is easier to use energy resources due to increasing pressure to cope with the public’s increasing power demands but harder to solve environmental issues due to political, social, ethical and economic considerations.
83
Q

What is specific heat capacity?

A
  • the specific heat capacity of a substance is the amount of energy required to raise the temperature of 1kg of the substance by 1°C

ZZ Phys 1 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions