1. P2 Topic 1 & 2

2. P2.1 Static Electricity +1 -1 1 0.0005 (almost zero)
The charge and mass of electrons, protons and neutrons
P2.1 Static Electricity
Proton
Neutron
Electron
Charge +1 -1
Mass 1
(almost zero)
Protons = positively charged
Electrons = negatively charged.
Electrons are in the shells of atoms.
Charge of an atom = neutral as the + and the – are equal.
Static electricity
In insulator can become charged by friction through the transfer of electrons.
A substance that gains electrons becomes negatively charged, while a substance that loses electrons becomes positively charged.
When a charged object comes near to another object they will either attract or repel each other.
If the charges are the same - they repel
If the charges are opposite - they attract

3. P2.1 Electrostatic Phenomena
The negatively charged balloon repels the electrons in the wall and they move away. The positive charge left behind attracts the balloon.
The negatively charged comb repels the electrons in the paper. The positive charge left behind is attracted to the comb which is why it picks up the paper.

4. P2.2 Uses and Dangers of static
How lightning is caused:
Static electricity can build up in clouds. This can cause a huge spark to form between the ground and the cloud.
A flow of charge through the atmosphere.
Static is dangerous when:
There are inflammable gases or vapours or a high concentration of oxygen. A spark could ignite the gases and cause an explosion.
You touch something with a large electric charge on it. The charge will flow through your body causing an electric shock.
Static electricity builds up on everyday objects. It can be dangerous if it can create a spark. A conducting path can be used to prevent sparking.
Earthing removes excess charge by movement of electrons.
The electrons flow through the earthing cable to earth rather than there being a discharge and spark.

5. P2.2 Uses and Dangers of static
Paint Spraying
1) The car is negatively charged.
2) The paint is positively charged. The positively charged paint spreads out as the repel each other.
3) The negative attracted to the positive and stick.
4) The metal spray nozzle is connected to the positive terminal of the power pack and the paint picks up a positive charge.
Air craft can build up a static charge when flying through the air and refuelling can also build a charge. To stop explosions the aircraft has a bonding line which is used to connect the air craft to the earth before it has been refuelled.
Insecticide sprays
Insecticide use static electricity.
Sprayed from aircraft so that they cover a large area.
Risk that some of the spray will blow away or fall unevenly. To prevent this, the insecticide is given a static charge as it leaves the aircraft.
The static drops spread evenly as they all have the same charge and are attracted to the earth.

6. P2.3 Electric Currents Materials contain electrons.
Insulating materials the electrons cannot move but in a metal they move and this can and this creates a current.
Key terms
Current is the flow of charge
Current in metals is the flow of electrons
Cells and batteries supply direct current (d.c.)
Direct current is the movement of charge in one direction.
Be able to use the equation:
charge (coulomb, C) = current (ampere, A) x time (second, s)
Q = I x t

7. P2.4 Current and Voltage. Voltmeter Ammeter Measures voltage in Volts
Measures current in Amps
Measures the energy difference between the electrons going into the component and back.
Electrons not used up out the output is the same as the input back to the cell.
Parallel
Series
No junctions
Current splits up at a junction
Potential difference measured.
Current size measured.
P2.4 Current and Voltage.
Potential difference is the energy transferred per unit charge.
1 Volt is 1 Joule per Coulomb

8. P2.6 Changing resistances
Resistance measures how hard it is for the electricity to flow through a circuit.
Measured in Ohms
Dependant on how many components are in the circuit.
The higher the resistance the lower the current.
Variable resistor = can change the resistance of a wire.
Be able to use the equation:
potential difference (volt, V) = current (ampere, A) x resistance (ohm, Ω)
V = I x R
Component
Resistance
Filament lamp.
As they get hot the resistance decreases. They get hot as they have a higher potential difference.
Diodes
Electricity flows in one direction. If a potential difference is applied in the other direct no current will flow.
Light dependant resistor
Resistance is high in the dark and low in the day time
Thermistor
High resistance when cold, low resistance when hot.

9. P2.6 Changing Resistances

10. P2.7 Transferring energy
Equations you must be able to use
Calculating Electrical Power
electrical power (watt, W) = current (ampere, A) x potential difference (volt, V)
P = I x V
Energy transferred (joule, J) = current (ampere, A) x potential difference (volt, V) x time (second, s)
E = I x V x t
A current in a wire is a flow of electrons . As the electrons move in a metal they collide with the ions in the lattice and transfer some energy to them.
This is why a resistor heats up when a current flows through.
Distinguish between the advantages and disadvantages of the heating effect of an electric current
Advantages
Disadvantages
Useful Heating a kettle
Wasted energy
Useful in Fires
Cause burns

11. P2 Topic 3
Force and Motion

12. Vectors and Velocity
Quantities which have a direction and size are known as VECTOR QUANTITIES.
4 Examples
Displacement – distance travelled in a particular direction.
Velocity – speed in a particular direction.
Force – always has a size and direction.
Acceleration – it has size and direction
Key equations you need to be able to use:
Speed (m/s) = distance (m) ÷ time (s)
Acceleration (m/s2) = change in velocity (m/s) ÷ time (s)

13. Distance/Time Graphs Horizontal lines mean the object is stationary.
Straight sloping lines mean the object is travelling at a constant speed.
The steeper the slope, the faster the object is travelling.
A curved line means acceleration.
To work out the acceleration, you need to calculate the gradient.

14. Velocity/Time Graph
Horizontal lines mean the object is travelling at a constant velocity.
Straight sloping lines mean the object is accelerating or decelerating.
The steeper the slope, the faster the acceleration.
A curved line means acceleration.
The area under the graph is the distance travelled.

15. Forces
A force is a push or a pull. When two bodies interact, the forces they exert on each other are equal in size and opposite in direction. These are known as REACTION FORCES.
You need to be able to interpret these diagrams and work out the resultant force in each direction.
If the resultant force is zero, it will remain at rest or continue to travel at a constant speed.
If the resultant force is not zero, it will accelerate in the direction of the resultant force.

16. Forces and Acceleration
The size of acceleration depends on:
Size of the force
Mass of the object
Key equation you need to be able to use:
Force (N) = Mass (kg) x acceleration (m/s2)

17. Terminal Velocity In a vacuum
all falling bodies accelerate at the same rate.
In the atmosphere
Air resistance increases with increasing speed.
Air resistance will increase until it is equal in size to the weight of a falling object.
When the two forces are balanced, acceleration is zero and TERMINAL VELOCITY is achieved.
Key equation you need to be able to use:
Weight (N) = Mass (kg) x gravity (N/kg)

18. Momentum, energy, work and power
P2 Topic 3
Momentum, energy, work and power

19. Stopping distance = thinking distance + breaking distance
Stopping Distances
Stopping distance = thinking distance + breaking distance
6 Factors affecting stopping distance:
Mass of vehicle
Speed of vehicle
Drivers reaction time
State of the breaks
State of the road
Amount of friction between the tyre and the road surface.
5 Factors affecting reaction time:
Age of driver
Drugs e.g. alcohol
Visibility
Tiredness
Distractions
Investigating friction. How much force is needed to move weights on different surfaces?

20. Momentum
A measure of motion. Mass multiplied by velocity. When a moving object collides with another object, the momentum is the same before the collision as it is after the collision.

21. If you increase the time you reduce the force.
Momentum and Safety
When you are travelling in a car (or on a bike, skis, train etc.) you are travelling at the same speed as the car. If the car stops suddenly, your momentum continues to carry you forward. If you are stopped suddenly, by hitting the dashboard (or ground) you experience a large force, and therefore a large amount of damage.
Car safety features:
Seatbelts – stretch to increase the time taken to stop, thus reducing the rate of change of momentum and reducing injury
Air bags – inflate to increase the time taken to stop, thus reducing the rate of change of momentum and reducing injury
Crumple Zones – crumple and fold in a specific way to increase the time taken to stop, thus reducing the rate of change of momentum and reducing injury
If you increase the time you reduce the force.
Use this formula:
Force (N) = change in momentum ÷ time

22. Work and Power Key definitions
Work – the amount of energy transferred. Measured in Joules (J)
Power – The rate of doing work. Measured in Watts (W). 1 joule per second is 1 watt.
Use this formula:
Work Done (J) = Force (N) x distance moved (m)
Example – if a 1kg mass (10N) is moved through a distance of 2 metres the work done is 20J.
Use this formula:
Power (W) = Work Done (J) ÷ Time taken (s)
Example – if a 24J of work is done over a 30 second period, the Power would be 24 ÷ 30 = 0.8W

23. Potential and Kinetic Energy
Key Definitions
Kinetic Energy – movement energy
Gravitational Potential Energy – the energy something has due to its position relative to Earth – i.e. its height.
Conservation of Energy
When energy is transferred, the total amount always remains the same.
You need to be able to use these equations: GPE = mgh KE = ½mv2

24. Topic 5 Nuclear Fission and Nuclear Fusion

25. P2.23 Isotopes Remember The Mass number is More that the atomic number
Keywords
Sub-atomic particles – a particle that is smaller than an atom
Nucleons – The subatomic particles in the nucleus of an atom e.g. protons and neutrons
Isotopes – Atoms of an element with the same number of protons and electrons but with a different number of neutrons.
Atoms
Atoms contain electrons, protons and neutrons = subatomic particles
Protons and Neutrons in the nucleus = they are called nucleons
All atoms on one element have same number of protons = atomic number
Mass number = number of protons and neutrons in the nucleus
Isotopes
Atoms with different number of neutron (same number of protons)
Different mass numbers
Examples
Lithium – 6 and Lithium-7
Carbon-12 and Carbon-14
An atom with a number attached referred to the isotope (as above)

26. P2.24 Ionising radiation Keywords
Unstable – an unstable nucleus is one that will decay and give out ionising radiation
Radioactive Decay – when an unstable nucleus changes by giving out ionising radiation to become more stable
Ion - An atom with an electrical charge (through loss or gain of electrons)
Ionising radiation
Alpha
Beta
Gamma
Particles containing 2 protons and 2 neutrons (Helium atom nucleus)
No electrons = 2+ charge
Emitted from nucleus at high speed
Lose energy as they ionise an atom
Produce many ions quickly so have short penetration distance
Stopped by a few cm of air of mm of paper
Electrons that are emitted from an unstable nucleus
Much less ionising that alpha
Can penetrate much further into matter
Stopped by a few mm or aluminium or even thinner lead.
High-frequency electromagnetic waves emmited by unstable nuclei
Travel at the speed of light
Ten times less ionising that beta
Penetrate matter easily
Stopped by a few cm of lead or many metres of concrete.

27. P2.25 Nuclear reactions Keywords
Nuclear fission– the splitting on a large nucleus.
Nuclear fusion – the joining of two small nuclei
Radioactive Decay
Releases energy
Alpha and Beta = kinetic energy
Gamma = energy in form of electromagnetic radiation
Nuclear Fusion
Small nuclei can combine to form larger ones
Also releases a lot of energy
Nuclear Fission
Nucleus splits into two smaller nuclei
Two or more neutrons also released
NOT the same as radioactive decay
If neutron are absorbed by other nuclei it can make them unstable – they then split releasing more nuclei = chain reaction (like an atomic bomb.
Can be controlled with materials to absorb neutrons (like in a nuclear reactor)

28. P2.26 Nuclear power Generating electricity Keywords
Moderator – a substance in a nuclear reactor which slows down neutrons so that they can be absorbed by the nuclear fuel more easily.
Radioactive waste – Material left over after the fission of uranium that is radioactive
Generating electricity
Thermal energy from core is transferred to coolant (usually water)
Coolant pumped through reactor
Coolant at high pressure pumped to heat exchanger to produce steam
Steam drives turbine which turns generator
Generator transfers kinetic energy to electrical energy.
Nuclear Reactors
Transform energy contained in nuclei of uranium and plutonium into thermal energy
Nuclear fission
Pellets of uranium inserted into hollow rods
Rods place in reactor core
Rate is kept constant but controlling the chain reaction
Number of free neutrons will not increase of decrease
Extra neutrons absorbed by control rods
Control rods placed in between fuel rods in reactor core
Control rods can be moved in and out to change the rate of fission
Fully lowered they shut down the reactor.

29. P2.27 Fusion – our future? Keywords
Peer reviewed – work checked by different scientists working in the same field
Validate – to confirm scientific theory is true
Scientists investigating fusion to generate electricity
The helium produced is not radioactive
Materials used to contain fusion do become radioactive
Getting new ideas accepted
Scientific theories have to be validated
By the scientific community
Report and results are peer-reviewed
Other scientists must carry out the experiment and get the same results
Fusion and temperature
The nuclei that fuse are both positively charged so repel = electrostatic repulsion
Nuclei need to be extremely close
High density nuclei are more likely to collide e.g. in the Sun the high gravitational field creates high density nuclei.
Difficult condition to create on earth
Fusion reactors try to produce high pressures and high temperature
High temperatures = more kinetic energy to overcome repulsion and collide.
These conditions require a lot of energy (more than the reactor can make so currently not very efficient)

30. Topic 6 Benefits and drawbacks of using radioactive materials

31. P2.28 Changing ideas Henri Becquerel and Marie Curie
Keywords
Hazards – causes of harm
Risk – likelihood of harm
Mutation – a change in the base sequence of DNA.
Henri Becquerel and Marie Curie
Accidental discovery was made that Uranium exposed photographic plates = discovery of radioactivity
Showed how radiation could ionise gases
Skin burns visible from handling Radium
By 1920s links made with cancer (Marie Curie died of lukaemia)
Large amount of ionising radiation = tissue damage (radiation burns)
Smaller amounts regularly = DNA damage (mutations)
Some mutations lead to cancer
Handling radioactive sources
Risk of harm decreases with distance from the source
Sources always handled with tongs
Risk reduced by not pointing sources at people
Keep sources in lead lined containers

32. P2.29 Nuclear Waste Advantages of nuclear power
Disadvantages of nuclear power
Station does not produce CO2
Less impact on global warming
Making the fuel rods requires energy (CO2 released)
Waste has to be stored for tens of thousands of years without leaks
People perceive it as unsafe after the Chernobyl accident
Low level Waste -
Only slightly radioactive
Remains so for tens of thousands of years
Clothing and cleaning materials from nuclear power stations
Hospitals also a source of LLW from radiotherapy cancer treatments
Compacted and buried in special landfill
Intermediate level waste
Remains moderately radioactive for thousands of years
Includes the metal cylinders that contained uranium fuel which become radioactive
Stored in concrete and steel containers
None disposed of yet
High level waste
The fission products from Uranium fuel are very radioactive
Produces large amounts of ionising radiation for about 50 years
Remains moderately radioactive for thousands of years as intermediate level waste
Transported in thick concrete and steel containers
Sealed in glass to prevent escape
Stored in canisters until it becomes ILW
Disposal methods
Firing into space
Risk of it falling back
Dumping in barrels at sea
Barrels can corrode
Enters food chain
Storage underground
Need geologically stable site
Low earthquake risk

33. P2.30 Half-life Radioactive decay
Unstable nucleus undergoes radioactive decay to become more stable
Activity of a substance is the number of nuclear decays per second
Measure in becquerel (Bq)
1Bq is one nuclear decay each second
Radioactive decay is a random process (cannot predict it)
Half life = the time taken for half the unstable nuclei in a sample of a radioactive isotope to decay.
Half life does not change as the sample gets smaller
After decaying = more stable nucleus
More stable nucleus = lower activity
Half life found by recording activity over a period of time.
Geiger-Muller tube
Used to measure radioactivity
Can be connected to a counter or may give a click when radiation detected
Count rate = number of clicks per second or minute

34. P2.32 Background radiation
Keywords
Background radiation – ionising radiation that is around us all the time from a number of sources. Some is naturally occurring.
Background count – the average number of counts recorded by a GM tube in a certain time from background radiation
Radon gas – naturally occurring radioactive gas that is emitted from rocks as a result of the decay of radioactive uranium
We are constantly exposed to ionising radiation – from space and naturally occurring = background radiation
Needs to be considered when measuring a source
Background count is subtracted from the source count
Background Radiation
Main source = radon gas
Released from decaying uranium in rocks
Diffuses into the air from rocks and soil
Medical sources = x-rays; gamma rays (scans) and cancer treatments
Some food are naturally radioactive
Cosmic rays = high energy charged particles from the stars (like the Sun) and supernovae, neutron stars and black holes.
Many cosmic rays are stopped by the atmosphere but some reach Earth.

35. P2.33 and P2.34 Uses of radiation
Diagnosis of Cancer
Gamma rays used
A tracer solution injected into body that collects in cancers
Gamma camera used to detect rays
Pass through the body so easily detected
P2.33 and P2.34 Uses of radiation
Sterilisation of equipment
To kill microorganisms surgical instruments need to be sterilised
Heat usually used but cannot be used on some things e.g. plastics
They are irradiated with Gamma rays instead.
Treatment of Cancer
Radiotherapy = ionising radiation to treat cancer.
Gamma rays used as beams to target and kill cancer cells.
Smoke Alarms
Contains a source of alpha particles
There is an electrical circuit with a gap between 2 charged plates.
Air in gap is constantly ionised therefore constant electric current.
When smoke get in the alpha particles are absorbed and stops the current drops = alarm sounds
Irradiating food
Bacteria will cause food to decay or make us ill
Gamma rays kill bacteria
Makes food safer and longer lasting
Does not make food radioactive
Foods like Fruit, cereals and shellfish are irradiated.
Tracers in the environment
Added to water to monitor pollution or leaking pipes underground
GM tube follows the pipe to detect leaks.
Checking thickness
Use a detector to measure the rate Beta passes through paper
Thinner paper = higher beta count.