1. Physics Paper 2 Revision
Written exam –
1 hour 15 mins combined
1 hour 45 mins triple
100 marks
50% of your GCSE
Physics Paper 2 Revision
Energy
Electricity
Particle Model
Atomic structure

2. Kinetic energy Any object that is moving has kinetic energy.
To work out the kinetic energy a body has you need to know its mass and its velocity:
Students need to recall equation

3. Elastic potential energy
An object that can stretch can store elastic potential energy e
Students need to apply this equation which will be given on the physics equations sheet
*Assuming the limit of proportionality has not been exceeded

4. Gravitational potential energy
Gravitational potential energy is the amount of energy an object has when it is held above the ground.
It is calculated using the following equation:
Ep(J)=m(kg)×g(N/kg)×h(m)
You will be given the value for g in any calculation
Students need to recall equation

5. Total energy(J)=GPE(J)+KE(J)
GPE and KE
Gravitational potential energy and kinetic energy are interchangeable.
If you get a question about a falling object the total energy is:
Total energy(J)=GPE(J)+KE(J)

6. Energy changes in systems
The amount of energy stored in or released from a system can be calculated. ΔE
The specific heat
capacity of a
substance is the
amount of energy
required to raise the
temperature of
1kg of the substance
by 1 degree Celsius
Students need to be able to apply this equation which is given on the physics equation sheet

7. Power
Power is the amount of work done or energy transferred every second and is calculated using the following equations:
Power(W)=Energy transformed(J) ÷ time(s)
Power(W)=Work done (J) ÷ time(s)
Students need to recall these equations W

8. Power definition
You need to be able to compare examples of power – here’s one…
More powerful engines in cars can do work quicker than less powerful ones. As a result they usually travel faster and cover the same distance in less time but also require more fuel. Increased fuel consumption costs more and has a bigger impact on the environment.

9. Useful and wasted energy
Energy cannot be created or destroyed but can be transferred usefully, stored or dissipated.
Where energy is being transferred the total energy stays the same. Some energy is always dissipated, usually as heat to the surroundings. We say this is dissipated.

10. How we can reduce energy loss?
Lubrication of engines cuts down energy loss by friction
Thermal insulation in houses can include Cavity wall,
Double glazing,
Fibreglass loft insulation.
How can we reduce cooling of a building?
Students ned to know that the higher the thermal conductivity of a material the higher rate of energy transfer by conduction through the material and that cooling of buildings is affected by thickness and thermal conductivity of the walls

11. Efficiency Two formulae (you need to recall both!)
Efficiency = useful energy out (x 100%)
total energy in
Efficiency = useful power out (x 100%)
total power in
You might need to rearrange these and put in the numbers.
Answers can be given either as a percentage (e.g. 30%) or as a decimal (0.3)  DO NOT combine these (e.g. 0.3%)

12. National and Global energy resources

13. Advantages and Disadvantages of different renewable resources
Students need to be able to consider the ethical, political, social, economic and environmental issues around global energy supplies

14. Electrical Energy Energy transferred = power x time
E (Joules) = P (watts) x t (seconds)
Energy transferred in kWh = power x time
E (kWh) = P (kW) x t (hours)
Cost of using electricity = number of kWh x cost per kWh
Electrical appliances are machines, they transfer energy from one form to another. For example, a light bulb takes in electrical energy and gives out light and heat; a hair dryer takes in electrical energy and gives out heat, sound, and kinetic energy.
Back

15. Exam Question
A rocket has a mass of 5000 kg and is travelling at a speed of 600 m/s. Calculate the rocket’s kinetic energy in kilojoules. Show your working.
correct with no working = 3 if answer incorrect, allow:
1 mark for K.E. =  × mass × speed2
2 marks for  × 5000 × 600 2
N.B. correct answer with the incorrectly recalled relationship
 × weight × speed 2 = 2 marks
[3]

16. Common circuit symbols

17. Static electricity – triple only
Insulators become
charged through
friction (rubbing).
Electrons move from
one object to the other.
Like charges repel
Unlike charges attract
Neutral objects are attracted to both positively and negatively charged objects.
Triple only

18. Electric Fields – triple only
An electric field surrounds a point charge as shown.
Note the direction of the arrows
on the + and – .charges
Electrostatic attraction occurs when the
two fields interact as shown.
If the voltage is sufficiently high, this may
cause a spark to be seen.

19. Current (Ampere,A) = Charge (Coulombs, C) ÷ Time(s)
For charge to flow through a circuit, there has to be a source of potential difference
Current is the rate of flow of electrical charges or electrons, i.e. the number of charges per second.
Current (Ampere,A) = Charge (Coulombs, C) ÷ Time(s)
Students need to recall this equation
Rearranged: Q = I t ; charge = current x time

20. Resistance Rearranged: R = V ÷ I; Resistance = voltage / current
Resistance is something that opposes the flow of current.
Voltage, current and resistance related by the equation: V = I x R
Rearranged: R = V ÷ I;
Resistance = voltage / current
Students need to recall this equation
Questions will be set using the term potential difference but responses will gain credit for either this or voltage

21. Exam Question Calculate the pd across the 8Ω resistor.
V = I x R
V = 0.5 x 8 = 4V
V = 9V – 4V = 5V
Calculate the pd across the 8Ω resistor.
What is the pd across component X?

22. I-V graphs
Current- potential difference graphs tell you how the current through a component varies with voltage.
Resistance of thermistor decreases as temperature increases – this is used in thermostats
Resistance of an LDR decreases as light intensity increases – used in security lighting

23. Series Circuits
The total resistance is the sum of the resistance of each component in the circuit.
Total resistance (Rtotal) = R1 + R2
The current is the same at every point in the circuit.
The voltage is shared between each component in the circuit.
Total voltage (Vtotal) = V1 + V2

24. Parallel circuits The voltage is the same across each branch
Vtotal = V1 = V2
The total current through the circuit is the sum of the current through each component
Total current (Itotal)= I1 + I2
The total resistance of two
resistors is less than the
resistance of the smallest
individual resistor

25. Exam Question
1. What is the total potential difference provided by the four cells in the circuit?
2. What will be the reading on the voltmeter?
3. The current through the lamp is 0.20 amps. The current through the resistor is amps.
What is the reading on the ammeter? 6V
6V (pd across cells is the same as the pd in each branch of a parallel circuit)
= 0.3A
Each cell provides a potential difference of 1.5 volts.

26. Direct current
In circuits which are powered by cells/batteries the current only flows in one direction, this is called direct current (d.c.).

27. Alternating current
Alternating current (a.c.) is what we receive from power stations and what comes out of plug sockets. This current changes direction constantly from positive to negative.
In the UK we use 230V at a frequency of 50Hz.

28. Mains Plug
Green/ Yellow
Brown
Blue
P.d. between live and earth I about 230V. Earth wire only
carries a current if there’s a fault.
Live wire may be dangerous even when switched off
Dangerous to provide any connection between live and
earth – electric shock

29. Earth
The Earth is a low resistance path for the current to flow through.
This means if the electricity has a choice of going through us or the earth wire, it will flow through the earth wire.

30. Calculating Power Power (W) Voltage(V) Current(A)
Power transfer in a circuit is related to p.d. and current
Power (W) = Current (A) x Voltage (V)
Power (W)
Current(A)
Voltage(V)

31. Calculating Power Substituting V=I xR: Power (W)
Power (W) = Current 2 (A) x resistance R (Ώ) P = I2R
Power (W)
Current(A)
Voltage(V)

32. p.d. (V) = energy (J) ÷ charge (C)
Voltage
Voltage or potential difference is the amount of energy transferred by the charges, i.e. the amount of energy per charge.
p.d. (V) = energy (J) ÷ charge (C)
Rearranged: E = Q V ;
Energy = charge x voltage

33. Energy transfers Electrical appliances transfer energy.
Amount of energy transferred depends on how long it is switched on for and the power of the appliance
Work is done when charge flows in a circuit
Energy(J) = Power (W) x Time(s)

34. Exam Question
A food processor is designed to transfer electrical energy to kinetic energy. However some of the energy is wasted as heat and sound. The power input to the food processor is 1150 W. The power of the spinning blade is 900 W. Calculate how much energy is wasted when the food processor is used for two minutes.
power × time = energy
time = 120 (seconds)
Wasted power = 1150 W W = 250 W
Energy = 250 W x 120 s = J

35. Energy transfer
Electrons are ‘pushed’ through an electrical circuit by the battery or other electrical supply.
Potential difference (voltage) is a measure of the electrical ‘push’.
The amount of energy transferred by 1 coulomb of charge (lots of electrons) depends on the p.d. that pushes it.
E=VQ

36. Exam Question
A small immersion heater was attached to a joulemeter. The voltage was set at 6 V d.c. The reading on the joulemeter at the start of the experiment was and 5 minutes later it was How much charged flowed in 5 minutes?
Energy = – = 1260 J
Charge = energy ÷ pd
Charge = 1260 ÷ 6 = 210 C

37. The National Grid
This is the network of cables and transformers linking power stations to consumers
Why is this an efficient way to transfer energy?

38. The arrows show the direction in change of state.
Particle Model
All substances are made of particles.
Particles cannot be squashed, but the gaps between them can change.
The state of matter tells you if it is solid, liquid or gas. Matter can change state.
This is a physical change .
The arrows show the direction in change of state.

39. Density
Density is determined by the mass of the atoms and how closely they are packed together.
Students need to recall this equation
Units:
Mass – kg
Volume - m3
Density – kg/m3

40. Internal Energy
is stored inside a substance by the particles (atoms or molecules)
Internal energy is the total kinetic energy and potential energy of all the particles
Heating the substance
up changes the stored
energy of the particles.
This either raises the
temperature or
changes the state. ΔE

41. Changes of State
Energy needed for a substance to change state is called
thelatent heat. This is the energy required to change the state
of 1kg of the material without changing the temperature
Energy (J) = mass (kg) x specific latent heat, L (J/kg)

42. Triple only – particle model and pressure
Particles in gases are always moving in random directions.
Pressure in gases is exerted by collisions with the sides of the container it is in.
Increasing the pressure of a gas increases it’s internal energy and hence its temperature.

43. Proton Charge = +1
Neutron Charge = 0
Electron Charge = -1

44. Atomic Structure
The atom has a radius of around 1 x m and the nucleus is around 1 ten thousandth of this size.
Most of the atom is empty space.
Isotopes have the same proton number and number of elsctrons but different numbers of neutrons

45. What happens when an atom loses or gain an electron?
They become ions.
Atoms with a charge that is not zero.
If an electron is lost the charge is positive.
If an electron is gained the charge is negative.

46. The discovery of the nucleus
Dalton’s Atomic Theory: Atoms are indestructible and indivisible (cannot be divided into smaller particles).
John Dalton ( )
Thomson’s Plum Pudding Model of the Atom: Thompson ( )
Thompson discovered the ‘electron’ .
So Dalton’s model of the atom was no longer acceptable because now there is something inside the atom.
Thomson believed the atom was made of positively charged matter with negatively charged electrons scattered throughout like plums in a plum pudding (or chocolate chips in chocolate chip cookie).

47. Ernest Rutherford ( ) wanted to test Thompson’s plum pudding model of the atom using his newly discovered alpha particles.
He carried out the ‘gold foil experiment in 1910:
He bombarded thin gold foil with a beam of ‘alpha’ particles. He expected it to be just like firing bullets at a tissue paper. “If the positive charge was evenly spread out like Thompson says, the beam should have easily passed through”.
Expected
Found
Conclusion: All of the positive charge, and most of the mass of an atom are concentrated in a small core, called the nucleus.

48. Development of Models of the Atom
Before the discovery of the electron, atoms were thought to be solid spheres that could not be divided Results from Rutherford’s
scattering experiment
showed that mass was
concentrated at the centre
and that most of the atom
was empty space. This lead
to the nuclear model.
Later experiments showed
that the nucleus contained
positively charged and
neutral particles called
neutrons (identified by James Chadwick.

49. Radioactive Decay
Some atomic nuclei are unstable and to become stable
they give out radiation. The Activity is the rate at which the atom decays - measured in Becquerels(Bq) by a detector called a Geiger Muller Tube.
There are three types of nuclear radiation:   
Properties to know :
Range in air α > β > γ
Penetrating power γ > β > α
Ionising ability α > β > γ

50. Types of radiation

52. Proton Number and Mass Number
The number of protons in an atom tells you what element it is.
The number of neutrons tells you if it is an isotope of an element.
Mass number = Number of protons + Number of neutrons.
Number of Protons and neutrons
Number of Protons (Also the number of electrons)

53. Decay Equations
No change to nucleus

54. Half-Life
The nuclei of radioactive atoms are unstable. They break down and change into a completely different type of atom. This is called radioactive decay. It is not possible to predict when an individual atom might decay. But it is possible to measure how long it takes for half the nuclei of a piece of radioactive material to decay. This is called the half-life of the radioactive isotope.
If the number of counts recorded on a Geiger counter starts at 100 and 3 hours later it counts 50; then the half life of that substance will be 3 hours.

55. Radioactive Decay is random -Half Life
The half life determines how hazardous the material, e.g. nuclear waste has half-lives
Of many thousands of years so remains harmful far into the future

56. Contamination and Irradiation
Contamination is the unwanted presence of materials contianing radioactive atoms on other materials The type of radiation emitted determines the hazard.
Irradiation is the process of exposing material to radiation – it doesn’t make the material radioactive itself, example food sterilisation, Xrays
Background radiation comes from rocks or cosmic rays from space or nuclear weapons testing or accidents. Dose is measured in Sieverts.

57. Uses of radioactivity – exploration of internal organs by scanning
The PET scanner detects
gamma rays
Radiation is used for the control or destruction of unwanted, diseased or cancerous tissues

58. Only Alpha and beta radiation are affected by electric and magnetic fields.

59. Fission and Fusion
Fusion is the joining of two
ligher nuclei to form a heavier
Onewith the release of energy.
Fission is the splitting of a large and unstable nucleus into two smaller
nuclei plus neutrons and gamma rays. All have KE. The neutrons go on to start a chain reaction.
Controlled chain reactions are used to release nuclear energy in a
power station. A nuclear weapon is an uncontrolled chain reaction

60. Nuclear Fission
Nuclear fission occurs when a Uranium-235 nucleus or a Plutonium-239 nucleus splits.
When a nucleus undergoes fission, it releases two or three neutrons which go on to cause further fission resulting in a chain reaction.
The energy released could be used to generate electricity.
The waste product is highly radioactive substances (Barium and Krypton) which need to be disposed of safely.

61. Nuclear Fusion
Nuclear fusion occurs when two small nuclei are forced close enough together so they join to make large nucleus.
Nuclear fusion is the process by which energy is released in the Sun. Energy is released when two nuclei are fused together.
The energy released could be used to generate electricity.
The waste product is Helium which is a harmless gas.
On the other hand it has technical difficulties as a very high temperatures are needed to start the fusion of nuclei.