Summary of each specification point for Edexcel P2.

1. P2 Topic 1 & 2

2. Proton Neutron Electron
Charge +1 0 -1
Mass 1 1 0.0005 (almost zero)
The charge and mass of electrons, protons and
neutrons
P2.1 Static Electricity
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. 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.
P2.2 Uses and Dangers of static

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.
Be able to use the equation:
charge (coulomb, C) = current (ampere, A) x time (second, s)
Q = I x t
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.

7. 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.
P2.4CurrentandVoltage.
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.
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.
Be able to use the equation:
potential difference (volt, V) = current (ampere, A) x resistance (ohm, Ω)
V = I x R

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
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
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.

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
Speed (m/s) = distance (m) ÷ time (s)
Acceleration (m/s2) = change in velocity (m/s) ÷ time (s)
Key equations you need to be able to use:

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. 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.
Terminal Velocity
Key equation you need to be able
to use:
Weight (N) = Mass (kg) x gravity (N/kg)

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

19. Stopping Distances
Stopping distance = thinking distance + breaking distance
6 Factors affecting stopping
distance:
1. Mass of vehicle
2. Speed of vehicle
3. Drivers reaction time
4. State of the breaks
5. State of the road
6. Amount of friction between
the tyre and the road
surface.
5 Factors affecting reaction time:
1. Age of driver
2. Drugs e.g. alcohol
3. Visibility
4. Tiredness
5. 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. 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:
1. Seatbelts – stretch to increase the time taken to stop, thus reducing the rate of
change of momentum and reducing injury
2. Air bags – inflate to increase the time taken to stop, thus reducing the rate of
change of momentum and reducing injury
3. 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
Use this formula:
Force (N) = change in momentum ÷ time
If you increase the time you
reduce the force.

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
You need to be able to use these
equations:
GPE = mgh
KE = ½mv2
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.

24. P2
Topic 5 Nuclear Fission and Nuclear
Fusion

25. P2.23 Isotopes
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.
Remember
• The Mass number is More that
the atomic number
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. 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)
P2.24 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
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)
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

28. P2.26 Nuclear power
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.
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.

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. P2
Topic 6 Benefits and drawbacks of
using radioactive materials

31. P2.28 Changing ideas
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
Keywords
Hazards – causes of harm
Risk – likelihood of harm
Mutation – a change in the base sequence of DNA.
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
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
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
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
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
Disposal methods
1. Firing into space
– Risk of it falling back
2. Dumping in barrels at sea
– Barrels can corrode
– Enters food chain
3. 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
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.
• 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

35. P2.33 and P2.34 Uses of radiation
Treatment of Cancer
• Radiotherapy = ionising radiation to treat
cancer.
• Gamma rays used as beams to target and kill
cancer cells.
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
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.
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.
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
Checking thickness
• Use a detector to measure the rate
Beta passes through paper
• Thinner paper = higher beta count.
Tracers in the environment
• Added to water to monitor pollution or
leaking pipes underground
• GM tube follows the pipe to detect leaks.