1
Q
How can an insulating material become charged? (2 points)
A
- Rubbed with another insulating material
- Electrons transfer from material to other
(one material left positively charged)
(one material left negatively charged)
2
Q
How can you generate static electricity? (2 points)
A
- Rubbing balloon, comb or strip of plastic against a jumper
- Electrically charged object can attract small objects
3
Q
What are 2 items that can become charged? (2 points)
A
- Dusting brushes (can be charged so that they attract dust when it passes over brush)
- Synthetic clothing (can become charged from friction between body and clothing when put on, when removed static sparks are sometimes produced)
4
Q
How can an object become discharged? (3 points)
A
- By earthing it
- Electrons are transferred from the object to the earth
- If you become charged then earthed, you may receive an electrostatic shock
5
Q
What are 2 nuisances of static electricity? (2 points)
A
- Dirt and dust can be attracted to insulating materials (TV screens/computer monitors)
- Some materials can statically cling to your skin
6
Q
What is repulsion and give an example? (2 points)
A
- 2 insulating materials with the same charge repel
- E.G. 2 positively charged Perspex rods will repel
7
Q
What is attraction and give an example? (2 points)
A
- 2 insulating materials with different charges will attract
- E.G. Negatively charged ebonite rod will be attracted to a positively charged Perspex rod
8
Q
What are 3 ways of reducing the chance of receiving an electric shock? (3 points)
A
- Making sure appliances are correctly earthed
- Using insulation mats effectively
- Shoes with insulating soles
9
Q
Why do certain lorries need to be earthed before unloading? (4 points)
A
- Contain inflammable gases, liquids or powders
- Friction causes a build up of charge
- Charge leads to spark
- Spark could ignite flammable substance
10
Q
How do anti-static sprays, liquids and cloths help to reduce the problems of static electricity? (2 points)
A
- Prevent the transfer of charge from one insulator to another
- So, if there’s no build up of charge, there can’t be any discharge
11
Q
What are atoms and molecules called that have become charged, and what are the 2 types of gained charge? (3 points)
A
- Ions
- Gain of electrons = negative ion
- Loss of electrons = positive ion
12
Q
How does electric/static charge build up, and what are the 2 types of build up? (3 points)
A
- Electrons rubbed off one material to another
- Material receives electrons = negatively charged (excess of electrons)
- Material gives electrons = positively charged (loss of electrons)
13
Q
How is static electricity used in spray painting, and what is another example of how electrostatics are used in this way? (6 points)
A
1) Paint particles gain electrons when passed through the nozzle of positive spray gun, gives a negative charge
2) These paint particles repel = forms a fine spray, even coat
3) Car panel has lost electrons so has a positive charge, which attracts the paint
4) As the paint sticks, the charges cancel, has neutral charge
5) A neutral charge means that no more paint will be attracted, so less paint is wasted, and all the sides (even shadows) are covered
6) In a similar way, electrostatics are used in crop-spraying
14
Q
How is static electricity used in defibrillators? (6 points)
A
- Electricity is used to stabilise irregular heartbeat
- They work by discharging electric charge
1) The 2 paddles are charged from a high voltage supply
2) Gel is used to make good electrical contact with the chest
3) Care is taken not to shock operator: - The paddles have insulating handles
- The operator and any one nearby stand clear
4) The charge is passed through the patient = heart contracts
15
Q
How is static electricity used in smoke precipitators? (5 points)
A
- Can remove smoke particles from chimneys
1) The metal grids in the electrostatic precipitator are given a high voltage
2) Depending on the design, the grids may be positively charged or negatively charged: - dust particles lose electrons if grids are positively charged
- dust particles gain electrons if the are negatively charged
3) Smoke particles pick up certain (above) charge
4) The charged dust particles then induce a charge on the earthed/oppositely charged metal collecting plates and the dust particles are attracted to the plates
5) The collecting plates are knocked to remove the smoke particles, which then fall into a collector
16
Q
What is a circuit? (1 point)
A
A complete loop that allows a current to flow
17
Q
How does a circuit work? (1 point)
A
Electrons flow around the circuit from the negative electrode of power source to positive electrode
18
Q
Why is a circuit shown as positive —> negative? (1 point)
A
The theory has only been discovered recently
19
Q
What are 2 important things for a circuit to work? (2 points)
A
- There must be a complete circuit
- There must be no short circuits
20
Q
What is resistance? (1 point)
A
Measure of how hard it is to get a current through a component in a circuit at a particular voltage
21
Q
What is resistance measured in? (1 point)
A
Ohms Ω
22
Q
What are the 2 types of resistor? (2 points)
A
- Fixed resistor = constant resistance, if resistance is increased, current decreases (and vice-versa)
- Variable resistor (rheostat) = changeable resistance, can be used to vary the amount of current in a circuit
23
Q
How can the resistance of the rheostat be changed? (2 points)
A
Changing the length of wire between the contacts
- Long wire = high resistance = low current
- Short wire = low resistance = large current
- Thin wire = not much space = high resistance
- Thick wire = more space = less resistance
24
Q
What is the formula of current, voltage and resistance, and what are they measured in? (1 point)
A
Resistance = voltage ÷ current
- Resistance is measured in ohms, Ω
- Voltage (potential difference) is measured in volts, V
- Current is measured in amperes (amps), A
25
For a given resistor, how does the current change as the voltage changes? (1 point)
For a particular resistor, if the voltage (potential difference) is increased the current increases (and vice-versa)
26
For a fixed voltage, how does the current change as the resistance changes? (1 point)
For a particular voltage (potential difference), if the resistance is increased the current decreases (and vice-versa)
27
What is the function of the live wire (brown)? (1 point)
Carried current to the appliance at high voltage
28
What is the function of the neutral wire (blue)? (1 point)
Completes the circuit and carries current away from appliance
29
What is the function of the earth wire (green + yellow)? (1 point)
Safety wire to stop the appliance becoming live
30
Why are mains electricity cables made of copper? (1 point)
Copper is a good conductor of electricity
31
Why are the outer layers of a mains electricity cable flexible plastic? (1 point)
Plastic is a good electrical insulator
32
Where does each wire of a plug go? (3 points)
- BLue goes Left
- BRown goes Right
- STriped goes to the Top
33
Explain why some appliances have double insulation (6 points)
- All appliances with metal outer cases (conductors) have earth wire and are earthed
- An earthed conductor cannot become live
- Appliances with insulator cases don't have an earth wire (they do have a fuse), because they have plastic casings, or they have been designed so that the live wire can not touch the casing
- As a result, the casing cannot give an electric shock, even if the wires inside become loose
- These appliances have double insulation
- Double insulated = can't become live
34
Explain how the earth wire and fuse work together? (5 points)
1) Fault in appliance = casing becomes live
2) Circuit short-circuits (swaps path of flow), as earth wire offers less resistance
3) Fuse wire melts
4) Circuit broken
5) Appliance and user are protected
35
What are fuses and circuit breakers? (1 point)
Safety devices designed to break a circuit if a fault occurs, prevents fires, injuries and deaths
36
What is a fuse, what is it for, what must it be, and how does a circuit breaker differ? (4 points)
- Short, thin piece of wire with low melting point
- Prevents cables/appliances from overheating
- Current rating of fuse must be just above normal current that flows through appliance
- On the other hand, a circuit breaker can be easily reset rather than replaced
37
What are the 4 stages of how a fuse works? (4 points)
1) Fault causes current in appliance to exceed the current rating of the fuse
2) Fuse gets hot and therefore melts/breaks
3) Circuit is therefore broken - current is unable to flow
4) Appliance and user are protected
38
What is the power rating of a device? (1 point)
How quickly electrical energy is being transferred into another form within
39
What is the formula for power, and what are they measured in? (4 points)
Power = voltage × current
- Power is measured in watts, W
- Voltage (potential difference) is measured in volts, V
- Current is measured in amperes (amps), A
40
Give an example of a fuse in action? (3 points)
1) If the current of appliance is below the current rating of the fuse, it works properly
2) If a fault occurs, live wire comes into contact with neutral wire, the current flowing is then higher than current rating of fuse, due to lower resistance
3) Cases fuse to get hotter until it breaks circuit. Current is unable to flow, so there is no danger of flex overheating (causes fire), damage to appliance and injuries prevented
41
What is ultrasound, and how does it travel? (2 points)
- Sound waves with frequencies of above upper limit of human hearing range (20,000Hz)
- Travels in longitudinal wave
42
What are the 5 key features of waves? (5 points)
1) Rarefaction - a region of lower pressure where particles are spread out
2) Compression - a region of higher pressure where particles are squashed together
3) Wavelength - the distance between 2 corresponding points on 2 successive disturbances
4) Frequency - no. of waves produced in 1 second, measured in hertz (Hz), a higher pitched sound has a higher frequency than a lower pitched sound
5) Amplitude - the maximum disturbance caused by a wave, the louder a sound is, the more energy it carries and the bigger its amplitude
43
What are 3 uses of ultrasound? (3 points)
1) To measure the speed of blood flow
2) To detect gallstones and tumours
3) Prenatal scanning - less risk to mother + babies than X-Rays
44
How do ultrasound waves break down kidney stones, and what are the benefits of using ultrasound for this? (5 points)
1) A high powered ultrasound wave is used to break down kidney stones by causing them to vibrate
2) Stones break up and disperse
3) Passed out of body in urine via the urethra
- Removed from body naturally
- Avoids the need for surgery
45
What are 2 advantages of using ultrasound over X-Rays? (2 points)
- Able to see soft tissues
| - Doesn't damage living cells
46
What is a transverse wave? (1 point)
The vibrations are at right angles to the direction of the wave
47
Describe particle motion in waves (1 point)
All waves transfer energy from one point ro another without transferring any particles of matter
48
How are visual images produced on a screen from ultrasound? (3 points)
1) Ultrasound is sent into the patient's body, the ultrasound waves are partially reflected at each boundary as they pass from one medium/substance into another
2) The time taken for these reflections to be detected can be used to calculate the depth of the reflecting surface
3) The reflected waves (echoes) are usually processed to produce a picture of the inside of the body on a screen
49
What makes ultrasound safer for a patient? (1 point)
The ultrasound waves used to image babies and soft tissue organs have small amplitude so are low energy, which makes it safer as no damage is done to any living cells
50
During decay, state the radiation given out by alpha, beta and gamma rays? (3 points)
- Alpha = helium nucleus
- Beta = fast-moving electron
- Gamma = electromagnetic wave (energy)
51
How is radiation measured? (1 point)
The no. of nuclear decays emitted per second, which decreases with time
52
Why is alpha radiation highly ionising? (4 points)
- Missing 2 electrons (has 2+ electric charge)
- Attracts electrons away from atoms it passes, leaves them positively charged
- They have a much larger mass, and a greater charge, than beta particles
- (Ionisation can be harmful to living cells)
53
(ALPHA) How does the nucleus of the new atom differ from the original? (4 points)
- Different element
- 2 fewer protons, 2 fewer neutrons
- Mass number decreased by 4
- Atomic number reduced by 2
54
(BETA) How is the nucleus of the new atom formed different from the original? (3 points)
- 1 more proton, 1 less neutron
- Mass number remains the same
- Atomic number increased by 1
55
What is half-life? (1 point)
The time it takes for half of the undecayed nuclei in a radioactive substance to decay
56
Give 2 ways that it is possible to date rocks? (2 points)
1) Measuring the proportion of lead and uranium in the rock
(The older the rock, the lower its uranium to lead ratio:
- Young rocks have a high uranium to lead ratio
- Very old rocks have a low uranium to lead ratio
2) Knowing the half-life of uranium
57
What is most background radiation released by? (2 points)
- Cosmic rays (radiation that reaches the Earth from space)
- Rocks and soil (some rocks are radioactive and give off radioactive radon gas)
- Living things (plants absorb radioactive materials from the soil and these pass up the food chain)
58
How is the radioactivity of an object measured? (2 points)
By the number of nuclear decays it emits each second – the more it emits, the more radioactive it is
59
In industry, what are tracers used for? (3 points)
- To track the dispersal of waste
- Find leaks/blockages in underground pipes
- Find the routes of underground pipes
60
Describe how a radioactive material is used in pipes and how the gamma is detected? (5 points)
1) A radioactive material that emits gamma is put into pipes
2) Gamma is used as it penetrates through soil to surface
3) The substances' progress is tracked by a detector above the ground
4) For a leak = the radioactive material escapes which is detected at the surface
5) For a blockage = the radioactive material stops flowing, so it cannot be detected after this point
61
How does the electric current flow in a smoke detector, and what happens if smoke enters? (6 points)
1) Most detectors contain americium-241, an alpha emitter
2) Emitted particles cause air particles to ionise, and the ions formed are attracted to oppositely charged electrodes
3) This results in the flow of an electric current
If smoke enters:
1) The alpha particles are absorbed by the smoke particles
2) This means less ionisation takes place
3) A smaller current than normal flows, and the alarm sounds
62
How can old, once-living materials (such as wood) be dated? (1 point)
By measuring the amount of carbon-14 left in its remains compared to the amount in living organisms
63
What is Carbon-14? (4 points)
- Carbon-14 is a radioactive isotope
- It is found in the air in carbon dioxide molecules
- The amount of carbon-14 in the air has stayed the same for thousands of years
- There is a small amount of radioactive carbon-14 in all living organisms because it enters the food chain
64
What happens when an organism dies, and the carbon-14? (2 points)
- Once an organism dies, it stops taking in carbon-14
- The carbon-14 it contained at the time of death decays over a long period of time, and the radioactivity of the material decreases
65
Explain what carbon dating is (5 points)
1) The amount of radioactive carbon-14 in the atmosphere has stayed the same for 1000s of years
2) Dead objects don't exchange with the air
3) As carbon-14 in dead object decays, it is not replaced, so the radioactivity of the sample decreases
4) The dead object has a different radioactivity to living matter
5) The ratio of the two activities is used to find the age of the object (within known limits)
66
How are X-Rays made? (1 point)
By firing high-speed electrons at metal targets
67
How are X-Rays and Gamma rays similar? (1 point)
- They are electromagnetic waves with similar wavelengths
| - They are ionising
68
How are medical radio-isotopes produced? (2 points)
1) Materials are put into a nuclear reactor where they are irradiated, forming the desired radioisotope
2) They become radioactive when they absorb extra neutrons
69
What is somebody in a hospital that uses X-Rays and radiation called? (1 point)
A radiographer
70
After alpha or beta decay, what does a nucleus sometimes contain? (3 points)
Surplus energy
- Emitted as gamma radiation
- Very high frequency electromagnetic radiation
71
Why are gamma and sometimes beta used as medical tracers, and how are they only in the body for a short time? (2 points)
- They can pass through the skin (unlike alpha)
- Radioisotopes with short half-lives are chosen to make sure that the tracer does not stay radioactive in the body for long periods, to avoid damage to healthy tissue
72
Contrasting to X-Rays, how are Gamma rays produced? (2 points)
- Gamma rays are given out by radioactive materials
| - This process is totally random and so cannot be controlled as easily as x-rays
73
What does the amount of absorption of X-Rays depend upon? (2 points)
The thickness and density of the material
74
How can materials become radioactive? (2 points)
- Materials do not become radioactive if they absorb electromagnetic radiation such as x-rays and gamma rays
- However, they can become radioactive if they absorb particles such as neutrons
75
Describe the 3 steps in which gamma rays are used to treat cancer (3 points)
1) A wide beam of gamma rays from a source outside the body is focused on the tumour
2) The beam is rotated around the outside of the body with the tumour at the centre
3) This concentrates the gamma rays on the tumour, and minimises damage to the rest of the body
76
What is an advantage and what are 2 possible health problems from using gamma radiation treatment? (2 points)
✓ Can destroy cancer cells without the need for surgery
✗ May damage healthy cells
✗ May cause sickness
77
What is a medical tracer? (3 points)
- Radioactive tracers are used to investigate a patient's body without the need for surgery
78
How is a tracer given to the patient? (2 points)
- By an injection
| - By ingestion (eating a solid with the tracer in it or drinking a liquid with the tracer in it)
79
How does a tracer work? (5 points)
- A small amount of radioactive material with a short half-life that is given to a patient
- The source used is either a beta or gamma emitter
- The radioisotope may be chemically attached to different substances, depending on the test being carried out
- The tracer is given enough time to move around the body before a radiographer positions a radiation detector outside the body
- This produces a picture showing where the tracer has accumulated
80
Why must the radioactive material emit either gamma or sometimes beta radiation? (2 points)
- They can penetrate body tissue
| - They can be detected outside of the body
81
How is nuclear radiation used in sterilising equipment? (4 points)
- Gamma rays are high energy electromagnetic waves which are only stopped by thick lead
- This means they can easily pass through medical equipment, such as syringes
- As gamma rays pass through the packaging they will inactivate viruses and kill bacteria
- As long as the equipment remains in a sealed plastic pack it will remain sterile
82
How are power stations used to produce electricity? (1 point)
They use energy sources - fossil fuel (coal, oil and gas) power stations and nuclear (uranium) power stations all use the same processes to make electricity from heat energy
83
What are the stages that power stations use to generate electricity? (4 points)
1) Conventional power stations burn fossil fuels
2) Fuel produces heat, used to boil water to make steam
3) Steam spins a turbine.
4) Turbine drives a generator and the generator makes electricity
5) Electricity goes to the transformers (step up/step down) to produce the correct voltage
84
How are nuclear power stations used to generate electricity? (3 points)
- Nuclear power stations use uranium
- They use the fission of uranium nuclei to generate heat to make steam
- The process of splitting a nucleus is called nuclear fission
85
What is nuclear fission? (1 point)
The process by which heat energy is released when a radioactive nucleus splits (Uranium)
N.B. This heat energy can be used in a nuclear reactor
86
Is uranium renewable or non-renewable? (1 point)
Uranium is a non-renewable energy resource and, like the fossil fuels, it cannot be replaced once it has all been used up
87
How is a chain reaction created in nuclear fission? (4 points)
1) The uranium nucleus must be hit by a neutron
2) When a uranium nucleus absorbs an extra neutron, it splits
3) This releases energy and more neutrons (2/3)
4) These neutrons cause further uranium nuclei to split
88
What are the 4 stages of small scale Nuclear Fission? (4 points)
1) The uranium atom is hit with a neutron
2) The nucleus splits into 2 smaller nuclei (e.g. barium and krypton)
3) Energy and new neutrons are released
4) The new atoms formed (barium/krypton) are radioactive
89
Why do nuclear fission chain reactions happen? (1 point)
Because each uranium nucleus that splits gives off more than one neutron, which causes more and more uranium nuclei to split
90
How are nuclear fission chain reactions controlled?
- A nuclear reactor is designed to allow a controlled chain reaction to take place
- Scientists stop nuclear reactions getting out of control by placing control rods in the reactor
- These control rods absorb some of the neutrons, so fewer neutrons are available to split uranium nuclei (prevents further fissions)
- The position of the control rods can be adjusted so there are just enough neutrons for the fissions' chain reaction to keep going
- Allows process to keep operating safely
91
Why can nuclear fission be dangerous? (1 point)
Produces radioactive waste
92
What is a nuclear bomb? (2 points)
- A chain reaction that has gone out of control, which results in one quick powerful release of energy
- Nuclear power stations are designed to keep chain reactions under control
93
What is nuclear fusion? (1 point)
The process by which 2 nuclei fuse together, and a large amount of heat energy is released, but only can occur at very high temperatures
94
Why is nuclear fusion not yet a possible energy source on Earth? (2 points)
- Scientists have not been able to produce the extreme pressures and high temperatures to keep a fusion reaction going for long enough for practical power generation
- And it is difficult to safely manage the extremely hot gases produced
95
In a fusion bomb, how are the initial high temperatures needed produced? (1 point)
By a nuclear fission reaction
96
Give 3 examples of nuclear fusion, and what happens? (4 points)
- Stars - extremely high temps/pressures (happens naturally)
- Fusion bombs (H-bombs/hydrogen bombs) - extremely high temps/pressures (started off by a fission bomb)
- Generating electricity - extremely high temps/pressures (difficult to achieve and maintain safely)
- 2 hydrogen nuclei join to form a helium nucleus to release energy
97
Why do scientists believe that it is worth trying to design and build a fusion power station, and why can one country not pay by themselves? (1 point)
- The oceans could provide almost limitless amounts of the hydrogen isotopes needed for nuclear fusion
- This is so expensive that several countries are working together on the project
98
Give the formula of 2 isotopes of hydrogen that undergo fusion? (1 point)
Deuterium (1,1H) + Tritium (2,1H) ---> Helium (3,2H)
99
What is cold fusion? (1 point)
A group of scientists have claimed that they have achieved ‘cold fusion’ - refers to a nuclear fusion reaction at ordinary (room) temperatures and pressures
100
What would happen if cold fusion works? (1 point)
If it happens, cold fusion could be developed to provide almost limitless and cheap electricity
101
If a cold fusion reaction can be controlled, what can the energy released be used for? (1 point)
Can be harnessed and used as an alternative energy source, replacing fossil fuels
102
Why has there been difficulty validating the cold fusion results? (1 point)
Some groups of scientists report that it happens while other groups are unable to get it to work
103
Who claimed to have achieved a cold fusion reaction, and when? (2 points)
- Martin Fleischmann and Stanley Pons
- 1989
- No-one had been able to successfully reproduce their experiment
104
How can cold fusion be made a realistic method of energy production? (2 points)
- Once data from cold fusion experiments are gathered in repeated experiments
- And the reaction is sustained to produce large quantities of energy
105
How can a new theory be accepted? (5 points)
1) Once experiments are identically repeated
2) Matching data (not anomalous) is collected
3) Shows discovery is genuine
4) Scientists must share data
5) Scientists across the world then replicate it
Additional Science
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