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GCSE Physics OCR A > P8 > Flashcards

P8 Flashcards

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1
Q

What is the speed of sound?

A

330m/s

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2
Q

What are the three fossil fuels?

A

⚫️Coal
⛽️Gas
🛢Oil
(All very energy dense)

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3
Q

What are the disadvantages of fossil fuels?

A

They emit carbon dioxide (greenhouse gases)
They are bad for the environment
They are NON- renewable sources of energy

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4
Q

What is the difference between a renewable source of energy and a non -renewable

A

Renewable: won’t run out as it is not used up when releasing energy
Non- renewable: will run out as it is used up

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5
Q

What are some examples of renewable energy sources?

A
  1. Solar ( energy from sun light)
  2. Wind (energy from the wind movement)
  3. Geothermal (energy from the earth’s heat)
  4. water high up in dams (hydroelectricity)
  5. tidal
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6
Q

How do fossil fuel power plants work?

A
  1. Fossil fuel is burned
    Through this chemical potential energy turns into kinetic energy
  2. The kinetic energy from burning the coal heats up water into steam
  3. The steam turns the turbine because of pressure
  4. Turbine turns the generator on
  5. The generator makes electricity
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7
Q

What is the greenhouse effect?

A

The earth’s atmosphere traps the suns heats

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8
Q

What are some advantages of fossil fuel power plants?

A

Reliable
Cost effective

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9
Q

How do nuclear power plants work?

A

The same way as fossil fuels but instead of burning a fuel , the kinetic energy comes from nuclear fission reactions

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10
Q

What are some uses for energy sources?

A
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11
Q

What are the disadvantages of nuclear power plants?

A

The radioactive waste is difficult to dispose of
It’s quiet dangerous.
Non- Renewable

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12
Q

What are the advantages of nuclear power plants?

A

No green house gases
Lots of energy per kg that fossil fuels (efficient)

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13
Q

What is a biofuel?

A

A renewable fuel that is obtained from the recent living.
Eg: methane gas from sewage, ethanol, sugars,wood.
✅carbon neutral

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14
Q

How are biofuels carbon neutral?

A

Carbon dioxide is given out when a biofuel is burned however as the plants photosynthesise they take the carbon dioxide back in

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15
Q

Why is coal non-renewable but wood renewable?

A

Coal takes millions of years to form, so it will run out before any new coal is formed. However wood only takes a few years to grow and so we can regrow it at the rate of our usage.

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16
Q

what is the difference between an energy fuel and an energy source?

A

sources: use energy flows , energy harnessed from natural resources
fuels: stores energy and must be extracted

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17
Q

How does electricity get sent to your homes?

A

Power plant —step up transformer—cables/pylons—step down transformer—home (mains/sockets)

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18
Q

What is the national grid?

A

A series of cables and pylons that transfer electrical energy generated from the power plant to homes and businesses.

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19
Q

What is the process of transfer for the national grid?

A

1️⃣Power station
2️⃣step up transformer
3️⃣cables and pylons
4️⃣step down transformer
5️⃣underground mains cable

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20
Q

What does a step up transformer do?

A

It increases the p.d, this decreases the current (as the power stays the same)
P=I✖️V
This minimises heat loss

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21
Q

How does decreasing the current decrease heat loss?

A

Normally when an electron hits a metal ion , it’s energy is transferred to the surroundings as heat.

Deceasing the current means that there are less electrons in the wires, therefore less hit ions and less release heat.

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22
Q

What does a step down transformer do?

A

It decreases the p.d
P= I ✖️V
This increases the current
Allowing appliances at home to run without causing problems

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23
Q

What problems do high p.d cause?

A

🟡risk of electrocution and death
⚪️ appliances need to have low p.d otherwise won’t work

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24
Q

What is the transformer power equation?

A

P=I✖️V
Power of each side of the transformer should be the same (primary circuit and secondary circuit)
(I✖️V) = (I✖️V)

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25
Q

What is the efficiency of a transformer?

A

efficiency of a transformer= power out (secondary circuits)➗power in (primary circuit)
✖️100

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26
Q

What is the average voltage in UK’s mains?

A

230v- average
330v -highest
-330v - lowest

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27
Q

What is the domestic electricity supply in the UK?

A

230v a.c at 50Hz

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28
Q

Describe the generator effect

A

A wire carrying no current is spun (force) within a magnetic field. As the wire cuts the field lines, electrons are slammed the corners. Now we have a p.d , allowing current to flow

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29
Q

What is direct current?

A

Electric current only flows on one direction
- provided by batteries and cells

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30
Q

What is alternating current?

A

Current which continually reverses direction.
Normally have higher p.ds

Current is alternating because p.d is alternating

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31
Q

Describe a voltage time graph for DC supplies

A

A horizontal flat line at one voltage

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32
Q

Describe a voltage time graph for an AC supplies

A

Basically a sine graph , with the highest value being 330 and the lowest being -330. But the average is 230

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33
Q

Why is the average 230?

A

Because more time is spent in that range

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34
Q

How is a high of 330v achieved?

A

Highest rate of cutting field lines because the wire is exactly perpendicular to the field lines

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35
Q

What happens to devices when 0 is hit?

A

Because of clever engineering the device can carry on.
However in the olden times the lights would not flash when they reached zero . This is because the change is too fast to see but would cause headaches as it was going down slightly

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36
Q

What does a voltage time graph look like for AC with a diode?

A

The sin graph, but all negative graph cut off from the bottom

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37
Q

Describe the live wire:

A

A brown wire, where current comes into the appliance

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38
Q

Describe the neutral wire

A

A blue wire, where current comes out of the appliance

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39
Q

Describe the earth wire

A

A green and yellow wire, that takes away extra electrons from the wrong place and leads them to the ground.
Is what saves YOU

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40
Q

Describe the fuse

A

A tube , next to the live wire. If current is too high then it will heat up and melt - stopping the current, before exit enters the device
It saves the APPLIANCE, and reduces the risk of fires

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41
Q

What is the difference between 2 core wires and 3 core wires?

A

2 core wires do not have an earth wire, only a live and neutral. This is because they are double insulated. 230 is such a low p.d , it cannot get through plastic

3 contain the earth wire

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42
Q

What is the longest pin on the plug?

A

The earth wire. If it is plastic, this is probably used for stability rather than a wire

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43
Q

What is the potential difference of a live wire in respect to the ground?

A

Ground =0
Live wire = 230v
=230v

44
Q

What is the potential difference of a neutral wire in respect to the ground?

A

Ground =0
Neutral =0
=0

45
Q

What are rectifiers and why are they used?

A

Rectifiers make the current flow in just one direction. They are used because appliance’s don’t like AC as it can increase resistance

46
Q

Why does the national grid produce alternating current?

A

Transformers only work with an AC
Without AC, the generators will only turn once

47
Q

Why do some plugs only have two wires?

A

Earth wire is not needed, because the appliance has no touchable metal parts which means the plastic is a DOUBLE insulator and therefore cannot become live

48
Q

Why is a high current fuse required?

A

🔹It must be above the normal working current for the appliance
🔹 otherwise it would blow under normal use

49
Q

What is the equation regarding the voltage and amount of coils

A

V input Primary coils
——— —————
V output Secondary coil

50
Q

Why do transformers require an Alternating Current?

A

🟠The A.C produces a changing magnetic field
🟡Needed to induce voltage

51
Q

How are radio waves produced?

A

An oscillating alternating current producing electromagnetic radiation

52
Q

What is a risk for people loving near a nuclear power station?

A

Leak of nuclear waste
Could contain it underground in thick lead walls

53
Q

What is a thermal power station?

A

A place where energy is used to heat up water

54
Q

Why is renewable energy good?

A

no

55
Q

Why are more power stations wanted?

A

To meet the demand for electricity

56
Q

What is the thinking distance?

A

The distance a car travels whilst driver is reacting, before brakes are applied
Human role

57
Q

What is breaking distance

A

Distance the car travels when a driver applies the break.
Machine role

58
Q

What is the stopping distance

A

Thinking distance + breaking distance

59
Q

What factors affect thinking distance?

A

🟣tiredness
🟣alcohol
🟣drugs
🟣distraction

60
Q

What factors affect breaking distance?

A

🟣weather
🟣worn tires
🟣faulty brakes
🟣badly maintained roads

They could decrease friction , increasing distance

61
Q

What is the definition of the Doppler effect?

A

An apparent change in the observed frequency/wavelength of a wave, due to relative motion between the observer and the source

62
Q

Describe the Doppler effect with sound wave

(Source moving towards you )

A

when the sound source moves towards you
🟢the wave peaks get closer together
🟢the wavelength gets smaller
🟢frequency / pitch of sound increases

63
Q

Describe the Doppler effect with light waves

(Source moving away from the

A

Light wave are harder to observe as there is a mich smaller wavelength
So relative motion between source and receiver must be large (stars and planets)

64
Q

Describe a red shift

A

The shift in wavelength of the light from the distant starts/ galaxies to longer wavelengths
*implies that distant stars/galaxies are moving away from us

65
Q

Describe a blue shift

A

The shift in wavelength of the light from distant stars/galaxies to shorter wavelengths

Implying that the galaxy/star is moving towards us

66
Q

How does the red shift provide evidence for the Big Bang?

A

Light from distant galaxies have red shifted, suggesting that they are moving away from us. Perhaps suggesting the ghat at one point all matter must have existed at a single point in space

67
Q

How do we know light is red shifted ?

A

Black lines correspond to the specific wavelengths of light absorbed by certain atoms in the star (since all stars contain hydrogen and helium. All spectra from stars contain a series of very specific black lines, which shift towards longer wavelengths implying light has undergone a Doppler shift.

68
Q

How does CMBR provide evidence for the Big Bang

A

Cosmic microwave background radiation,
At the beginning all energy in universe would have had very Short wavelength gamma wavelengths. As the universe expanded, this gamma radiation would have streckten out into longer wavelengths….. currently microwaves.

as CMBR is evenly distributed across the universe , Suggest that they all started off from a single point

69
Q

What is the definition of the big bag ?

A

A theory that takes all the energy and mass of the universe was contained within a single point in space (no volume ) which meant that it had infinite density. Then all the universe started expanding very rapidly.

70
Q

What is the composition of the solar system?

A
71
Q

How did the sun and the solar system form?

A

Formed from the remains of a supernova
Clouds and dust were pulled together by the force of gravity. When enough gas and dust has gathered and became dense enough to start nuclear fusion, a protostar formed. The protostar becomes denser and hotter, particles gain kinetic energy and collide allowing nuclear fusion to begin, forming a main sequencing star

72
Q

What are the two overall forces adding upon a star/planet?

A
73
Q

What is the life cycle of a star?

A
74
Q

Describe the life cycle of a small mass star

A

1) dust and clouds formulate, with a gravitational pull to form a protostar
2) when protostar is dense enough to do nuclear fusion, it becomes a main sequencing star
3) as fusion starts, the radiation pressure becomes greater than the gravitational pull, causing the star to expand into a red giant
4) the nuclei for fusion will eventually run out, reducing the radiation pressure, causing the planned to collapse into smaller planet. However since the volume of the planet has decreased the temperature increases leaving a white dwarf planet.
5) once the white dwarf cools, it becomes a black dwarf

75
Q

Describe the life cycle of a larger mass star

A

1) the dust and air form a protostar under gravity
2) when the protostar becomes dense enough for nuclear fusion, it then becomes a main sequencing star (equilibrium)
3) Due to the nuclear fusion, the radiation pressure increases, becoming stronger than the gravitational force, cause it to expand into a red supergiant
4) when helium nuclei run out for fusion , starts to fuse together heavier Elements, resulting in a further increased Radiation pressure, enough for the explode into a supernova
5) from this super nova a neutron start is made, if it is dense enough then it is known as a black hole.

76
Q

What is temperature?

A

The measure of the average kinetic energy of particles of a system

77
Q

What happens to the particles when there is a greater temperature ?

A

More kinetic energy,
The faster the particles will displace, rotate and vibrate

78
Q

What happens when charged particles vibrate?

A

The emit EM waves

79
Q

What happens if the temperature of charged particles increases?

A

They vibrate faster, emitting a higher frequency of EM radiation

So blue bodies are hotter than red bodies

80
Q

When will the temperature of a body decrease?

A

If the body emits more radiation than absorbs

81
Q

When will the temperature of a body increase

A

If it absorbs more energy than emmits

82
Q

Graph of frequency and intensity of radiation at each frequency

A
83
Q

Describe the Earth’s structure

A

A liquid outer core, able to do so because of pressure

84
Q

Describe a P wave

A

A primary wave, comes first (longitudinal waves) can travel through solids and liquid
*more damaging

85
Q

Describe an S wave

A

Secondary wave, a transverse wave, can only travel through solids
(Shaking up and down)

86
Q

What is an earthquake?

A

When forces inside the Earth become large enough to break and move layers of rock.

Earthquakes originate in the Earth’s crust.

87
Q

What is a focus point ans an epicentre of an earthquake

A

Focus point is where the Seismic wave originated and the epicentre is the nearer point of the surface to the focus

88
Q

How to p waves and S waves travel through the Earth?

A
89
Q

How can you detect P waves and S wave ?

A

Sesiometers

90
Q

What is the difference between inner plants and outer plants?

A

Inner planets: mercury, Venus, Earth and Mars
Have a rocky atmosphere and a smaller mass

Outer planets : Jupiter, Saturn, Uranus, Neptune
Mostly made out of bass, have larger masses and gravitational fields

91
Q

What are “seismic waves”

A

A collective term for P waves and S waves

92
Q

What is a satellite?

A

Any body that orbits A star

93
Q

What is a natural and artificial satellite?

A

Natural satellites = moon, of earth, earth of sun
Artificially satellites= communication satellites that orbit around Earth

94
Q

What a geostationary orbit ?

A

🔵A satellite that orbits the earth every 24 hours. 🔵Launched at the equator, appears to stay in the same position give the earth’s surface (rotation is parallel to earth’s )
🔵In the horizontal plane
Eg: communication , GPS

95
Q

What is a low polar orbit ?

A

🔵rotation is perpendicular to earth’s orbit, can can the surface of the earth very quickly

Eg: weather satellites

96
Q

What are elliptical orbits?

A

An orbit that doesn’t have a fixed radius, but a specific point we assume it has a central orbit

97
Q

What forces are acting upon a planet orbiting it’s star

A

Since direction is constantly changing, so it the velocity. This must mean there is an acceleration, and so there is a resultant force.
A.k.a a centripetal force

98
Q

Describe the forces acting upon a satellite

A
99
Q

What is a stable orbit

A

Maintains a constant radius about the body it is orbiting

100
Q

How does the speed of the satellite correlate to the orbit ?

A

If too slow, gravitational attraction will pull in

If too fast then gravitational attraction is not enough and satellite flies away

*the larger the distance from the body the slower the speed of the satellite needs to be to maintain a constant orbit, (longer time period)

101
Q

Why do geostationary satellites have to be launched at the equator?

A

Ensures that the satellite’s plane of orbit, matches the plane of rotation of the earth allowing it to maintain a fixed position relative to the earth.

102
Q

why have uses of different energy ssources changed over time?

A
  • increasing population
  • use of devices that use fuels (engines, cars-use of oil)
  • electricity generation

industrial revoltion (coal increase in oils)

103
Q

how is potential difference generated in the national grid?

A

across wires

104
Q

What are some dangers of live wires, even if the switch in mains circuit is open ?

A

The live wire may become loose inside an appliance, it can touch a metal casing. If someone touches the casing there will be a potential difference of 230v (0 you) and (230v live wire). A dangerous current could flow through you

105
Q

What are some preventions for dangers to prevent current flowing through you ?

A

Earth wire : connects case to pole in the ground, less resistance that you, discharging the current
OR
case made of plastic and is a double insulator (no earth pin), as charge cannot flow through the double insulated case to you

GCSE Physics OCR A (13 decks)

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