P1 Flashcards
(119 cards)
0
Q
Name three ways in which heat is transferred.
A
Conduction, convection or radiation.
1
Q
Most heat in solids is transferred by…
A
Conduction
2
Q
What do all objects do with infrared radiation?
A
Emit (give out) and absorb (take in)
3
Q
Convection heat transfer happens mostly in…
A
Liquids and gases
4
Q
What is a good absorber and a good emitter of infrared radiation?
A
Something with dark, matt surfaces
5
Q
The bigger the temperature difference between a body and its surroundings….
A
the faster the energy is transferred by heating
6
Q
What is the particle structure in a solid?
A
Strong forces, arranged in a pattern, don’t have much energy so they only vibrate
8
Q
What is the particle structure in a solid?
A
Strong forces hold particles close together, arranged in a pattern, don’t have much energy so they only vibrate in fixed positions
8
Q
Explain conduction of heat in a solid.
A
Vibrating particles pass on their kinetic energy to the particles next to them until all the heat is passed through
9
Q
What is the structure of a liquid?
A
Weaker forces, more energy but move in low speeds in all directions. Particles are close together but arranged in irregular pattern, can move past each other
11
Q
Explain Why are metals such good conductors?
A
Free electrons which are free to move. At the hot end the electrons are moving faster and collide with other free electrons which transfer heat energy. Much faster in metals because of free electrons colliding more often
12
Q
Explain convection of heat.
A
Convection happens when more energetic particles MOVE from the hotter region to the cooler region and take their heat energy with them
12
Q
What is condensation?
A
When a gas cools, the particles slow down and lose energy. The attractive forces between particles are pulled closer together. If gas particles get close enough together, condensation happens and the gas becomes a liquid.
13
Q
How is all the water heated in a heater?
A
Heat is transferred from heater coils to water by conduction. Particles near the coils get more energy so start moving faster, this means more distance between particles. water expands and becomes less dense. Less dense particles (hot) rise above denser particles (cool). The hot water displaces (moves) colder water out the way making it sink towards heater coils. Cold water is heated by coils - convection currents circulating the heat energy through the water
14
Q
The rate of evaporation will be faster if the..
A
Temperature of a liquid is higher.
Density of a liquid is lower
Surface area of a liquid is larger
15
Q
The rate of evaporation will be faster if the..
A
Temperature of a liquid is higher.
Density of a liquid is lower
Surface area of a liquid is larger
Airflow of a liquid is greater
16
Q
What does it mean for heat transfer if an object has a big surface area?
A
Heat transfer is quicker because more infrared waves can be emitted from the surface or absorbed.
17
Q
Name one good insulator of heat.
A
Plastic
18
Q
How do you work out cost effectiveness?
A
Payback time = Initial cost / annual saving
19
Q
For loft insulation, a thick layer of fibreglass wool would be laid out across the whole loft floor. What two types of heat transfer are reduced?
A
Conduction and radiation
20
Q
How do you work out cost effectiveness of an object?
A
Payback time = Initial cost / annual saving
21
Q
In a hot water tank, what can be used to reduce conduction and radiation heat transfer?
A
Surround the tank in an insulating material, e.g. Fibreglass wool
22
Q
If you want to reduce convection and radiation heat transfer in your house, what could you do?
A
Use foam squirted between bricks - cavity wall insulation
23
Q
What does the specific heat capacity tell you?
A
How much energy an object can store
24
What do these symbols stand for?
| E = m x c x θ
E= energy transferred (J) C = specific heat capacity (J/kg°C)
M=mass (kg) θ = temperature change (degrees celsius)
25
What are the nine types of energy?
Electrical, light, sound, kinetic, nuclear, thermal, gravitational potential, elastic potential, chemical.
26
Energy can be transferred, stored or spread out but never...
Created or destroyed
27
What is the energy transfer of a battery?
Chemical -> electrical -> heat
28
What is the energy transfer of firing a bow and arrow?
Elastic potential -> kinetic -> heat
29
How can you represent an energy transfer for a tv?
Use a sankey diagram
30
How do you work out the efficiency of a device?
Useful energy/power out / total energy/power in
31
How does a sankey diagram work?
The thicker the arrow, the bigger the amount of energy thats either wasted or useful.
33
Name four non-renewable energy resources.
Coal, oil, natural gas, nuclear fuels (uranium and plutonium)
33
How does a renewable energy source work?
The energy source uses water/steam/air to turn a turbine which turns the generator to produce electricity.
34
Name 8 renewable sources.
Wind, waves, tides, hydroelectric, solar, geothermal, foodbiofuels
35
What is the difference between wind power and hydroelectric power?
Wind power is generated directly from the WIND which turns the blades (turbines) and turns the generator. Very noisy and not 100% reliable. Hydroelectric power uses falling WATER to turn the turbine which turns the generator. Can look ugly, animals can lose habitats, more reliable unless there is no rain in a long time.
37
Explain wave power and some pros and cons
As waves hit shore, they provide up and down motion which can be used to drive a generator, No pollution, no fuel costs. However, unreliable, spoil the view and be a hazard to boats.
38
What is geothermal energy and why is it a good idea?
In some volcanic areas, steam and hot water rise to surface and this steam turns a turbine to turn a generator. It doesn't ruin wildlife habitats, no pollution or waste, cannot be seen too much. However, not many suitable locations for it
38
What are biofuels made from? State two advantages.
Crops like sugar cane can be fermented to produce ethanol, or plant oils can be changed to produce biodiesel. Cheap and quick to make.
39
Explain tidal barrages and state two advantages and disadvantages.
As the tide comes in, it fills up the estuary and drives a turbine at controlled speeds.
Very reliable, doesn't produce harmful waste. Can destroy animal habitats, and can spoil the view.
40
What do fossil fuels release into the air and why is it bad?
Carbon dioxide. This is bad because it adds to the greenhouse affect. It produces sulfur dioxide, and contributes to global warming.
41
Why could nuclear power be so dangerous?
If there is an explosion at the power plant, harmful materials could be released and could damage people. Nuclear waste is difficult to get rid of and is very dangerous.
42
What is bad about coal mining?
Makes a mess of the landscape, destroys wildlife habitats and creates a big eye-sore.
43
How does carbon capture and storage (CCS) work?
It works by collecting CO2 from power stations before it is released into the atmosphere. Captured CO2 is pumped into empty gas fields, and stored safely.
44
State three disadvantages of biofuels.
Large areas of forests have to be cleared to make room to grow biofuels. When biofuels are burnt CO2 is released into atmosphere. Species can lose their natural habitats when forests are destroyed.
45
Why is it better to have an extremely high voltage and very low current?
Because having a high current loses loads of energy through heat in cables.
46
What does the national grid do?
Takes electrical energy from power stations to where it's needed in homes or industries. You need a high voltage or high current
47
What is a step up transformer?
It increases the voltage up to 400 000 V at one end.
48
What is a step down transformer?
The voltage is reduced to safe useable levels.
49
Sum up the pros and cons of overhead and underground cables.
Overhead cables have a lower start up cost whereas underground cables are higher. However underground cables are well hidden unlike overhead which are ugly and affected by weather. Underground cables are not affected by weather and are more reliable than overhead.
50
What does frequency mean and what is it measured in?
Number of complete waves passing a certain point per second. Measured in hertz
51
What is a longitudinal wave?
Vibrations are parallel to the direction of energy transfer. Compressions are when the wave is bunched up, rarefactions is when the wave is spaced apart.
52
Describe a transverse wave.
Vibrations are at 90° to the direction of energy transfer. (perpendicular) Most waves are transverse.
53
What is the law of reflection?
Angle of incidence = angle of reflection
54
What are the seven types of electromagnetic wave?
Radio, micro, infrared, visible light, ultraviolet, x-rays, gamma rays.
55
If an electromagnetic wave has a higher frequency, would the wavelength be longer or shorter?
Shorter
56
What is the doppler effect?
When something that gives out waves moves towards or away from you, the wavelengths and frequencies seem different compared to when the source of the waves is stationary.
57
What is red shift?
Different chemical elements absorb different frequencies of light. Each element produces a specific pattern of dark lines at the frequencies that it absorbs in the visible spectrum. So When we see light from distant galaxies we can see the same patterns but at slightly lower frequencies than they should be - they're shifted towards the red end.
59
True or false: the further away a galaxy is, the greater the red shift.
True
60
Heat radiation is the transfer of heat energy by...
infra red radiation
61
What do conduction and convection involve?
transfer of energy by particles
62
How much radiation does a hotter object than its surroundings emit?
emits more radiation than it absorbs. Gives out more as its cooling down
63
How much radiation does a cooler object than its surroundings emit?
Less radiation than it absorbs. Absorbs more as it warms up
64
What is the kinetic theory?
Describes how particles move in solids liquids and gases dependant on their energy
65
Describe the structure of a gas
almost NO forces of attraction between particles. More energy than liquids and solids. Free to move and travel in random directions at high speeds
66
What sort of objects is conduction faster in and why?
Denser solids, particles are closer together so will collide more often and pass energy between them.
67
What are convection currents all about?
Changes in density
68
What happens to water vapour in the air when it comes into contact with cold surfaces?
condenses
69
What is evaporation?
when particles escape from a liquid
70
Explain evaporation
The fastest particles in a liquid are most likely to evaporate from the liquid - so when they do, average sped and kinetic energy of remaining particles decreases. Decrease in particle energy causes liquid to cool because of temp. decrease
71
How can a particle near the surface escape and become a gas?
particles are travelling in right direction
| Particles are travelling fast enough to overcome attractive forces between other particles of liquid
72
What things do the rate of condensation depend on to make it faster?
Temperature of the gas is lower
Temperature of the surface the gas touches is lower
Density is higher
Airflow is less
73
Why do some motorbike and car engines have "fins" on them?
Because they increase the surface area so heat is radiated away quicker - engine cools quicker
74
What are "heat sinks" devices?
Designed to transfer heat energy away from objects they're in contact with - computer components.
75
How do humans prevent heat loss whens its cold?
Hair on skin "stand up" to trap a thicker layer of insulating hair around the body. - limits amount of heat loss by convection
76
Why do people go pink when they're hot?
Because body diverts more blood to flow near the surface of your skin so that more heat can by lost by radiation
77
What is draught proofing, how is it useful?
strips of foam and plastic around doors and windows stop draughts of cold air blowing in - reduce convection heat loss
78
What does a U-value show?
how fast heat can transfer through a material
79
How do heaters have high heat capacities to store lots of energy?
Materials used usually have high specific heat capacities.
80
How are gravitational potential, elastic potential and chemical energy different from the other types?
They are forms of stored energy. They don't do anything, they're waiting to be turned into one of the other forms.
81
When is energy only useful?
Its only useful when it can be converted from one form to another
82
What is a common form of energy that is often wasted?
heat
83
What is the rule about a device being 100% efficient?
No device is 100% efficient and the wasted energy is usually spread out as heat..
84
Which is the ono device that can be 100% efficient and why?
Electrical heaters. All electricity is converted to heat.
85
Why do we call it wasted heat? And how is all energy spread out eventually?
Because nothing can be done with it. All entire energy output by a machine usually ends up as heat. The heat is transferred to cooler surrounding which become warmer. As the heat is transferred to cooler surroundings the energy becomes less concentrated - total amount of energy stays the same but as it spreads out more, its difficult to collect back or be used.
86
Whats two way you can calculate cost of something?
COST = units x price per unit
| no. of units (kWh) used = power (kW) x time (hours)
87
How do you read an electricity meter?
units usually in kWh. To work out total energy used over a time period - subtract meter reading at start from the reading at the end
88
How does electricity affect standard of living?
Refrigerators keep food fresh to slow down growth of bacteria and keep vaccines cold.
Can improve public health - X-ray machines use electricity
Communication - telephone, internet
89
How does a nuclear reactor work?
They're just fancy boilers. Nuclear fission producing heat to make steam to drive turbines etc. They take the longest time to start up.
90
Explain solar cells and some pros and cons
Solar cells generate electric currents directly from light. Used for calculators and watches - don't use much electricity. Often used in remote places, no pollution and in sunny countries its a very reliable source. However, only works in day time. Initial cost are high but after that its free.
91
What does it mean by pumped storage?
Large power stations have huge boilers which run through the night when demand is low. Difficult to store spare energy - pumped storage best solution. - spare night time electricity is used to pump water up to a higher reservoir. It can be released quickly during periods of high demand. Pumped storage uses same idea as hydroelectric but it DOESNT generate power its a way of storing already generated power.
92
What things need to be taken into account when setting up a power station?
How much set up cost is, how long it takes to build and then run, how much power it can generate, impact on environment and local people, location And getting permission to build it
93
What are some environmental issues when setting up a power station?
Any atmospheric pollution, visual pollution, disruption of habitats and leisure activities, noise pollution and things breaking.
94
When setting up a power station, what sort of stations would need to be considered location wise?
Hydroelectric - hilly rainy places
Wind - exposed windy places
Waves - near coast
Nuclear - away from people and near water
95
Why is set up/decommissioning time important when setting up a power station?
Affected by size of power station, complexity of engineering and also planning issues. GAs is one of quickest to set up and nuclear is the longest.
96
What sort of waves are transverse?
Light and all other EM waves, waves on strings, ripples on water
97
What sort of waves are longitudinal?
Sound waves and ultrasound. Shock waves.
98
how do you work out speed of a wave?
frequency x wavelength
99
What are some important points when showing how an image is formed in a PLANE MIRROR?
Image is same size as the object
It as as far behind the mirror as the object is in front
Image is virtual and upright
left and right sides a re swapped - laterally inverted
100
Explain diffraction of a wave
Waves spread out at the edges when they pass through a gap or pass an obstacle. Amount of diffraction depends of size of gap relative to the wavelength of the wave.
101
(diffraction) The narrower the gap of an obstacle...
the longer the wavelength, the more the wave spreads out
102
Explain refraction of a wave
When a wave crosses a boundary between two substance it changes direction. If a light wave meets a different medium at an angle, the wave changes direction,
103
Give an example of refraction
When light shines on a glass window pane, some light is reflected but some passes through and get refracted.
104
5 thing about Radio waves
wavelengths longer than about 10cm
Mainly used for communication
Long radio waves can be sent from London and received half way round the world - wavelengths diffract (bend)
short radio signals can be received at long distances - because waves a re reflected from ionosphere
radio waves used for TV and FM radio have short wavelengths
105
about microwaves
used for satellite communication and mobile phones
for satellite TV - signal from transmitter is transmitted into space where its picked up by satellite receiver dish satellite transmits signal back to earth in different direction
microwaves used by remote-sensing satellites
106
Infrared waves
used fro remote controls and optical fibres
| emitting different patterns of infrared waves to send different commands to an appliance
107
Visible light waves
Useful for photography
camera uses lens to focus visible light onto a light-sensitive film or electronic sensor
lens aperture controls how much light enters the camera
108
sound waves
sound waves are caused by vibrating objects
sound waves caused by vibrating particles - denser the object the faster the sound travels.
They can reflect and refract
109
Sound waves are reflected by...
hard flat surfaces
110
Why does sound, sound different in a empty room compared to a room containing furniture?
Furniture or objects absorb the sound quickly to stop it echoing. Echoes are reflected sound waves
111
How does a sound wave refract?
They refract as they enter a different media
112
Higher frequency means....
high pitched and shorter wavelengths
113
Lower frequency means...
low pitched
114
What is the big bang theory?
All the matter and energy in the universe must have been compressed into a very small space. Then it exploded and started to expand. Expansion is still happening and we can use the rate to discover the age of the Earth.
115
Whats the "steady state" theory?
the universe has always existed as it is now and it always will do. Universe appears the same everywhere - lots of problems with this theory
116
what is CMBR
cosmic microwave background raidiation
117
What can scientists detect about radiation?
low frequency electromagnetic radiation coming from all parts of the universe
118
How is the big bang theory the only theory that explains the CMBR?
universe was extremely hot and everything emitted very high frequency radiation. As the universe expanded it has cooled and this radiation dropped in frequency and is now seen as microwave radiation
119
How does the big bang theory have its limitations?
some people still believe in the steady state theory.
its not the whole explanation of the universe - observations the theory cannot explain
its not an explanation for what caused the explosion in the first place
