AQA A-level Syllabus

Year 2 (A-Level)

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Periodic Motion   Thermal Physics   Gravity Fields    Electric Fields   Capacitors   Magnetic Fields    Radioactivity

3.6 Further mechanics and thermal physics

3.6.1 Periodic motion

3.6.1.1 Circular motion

3.6.1.2 Simple Harmonic Motion (SHM)

Motion in a circular path at constant speed implies there is an acceleration and requires a centripetal force.


Magnitude of angular speed:


Radian measure of angle.


Direction of angular velocity will not be considered.


Centripetal acceleration

 

The derivation of the centripetal acceleration formula will not be examined.
 

Centripetal force

 

 Further Mechanics 1

(Circular Motion)

 

Further Mechanics 2

(Examples)

 

Analysis of characteristics of simple harmonic motion  (SHM).


Condition for SHM:

 


 

Defining equation:



Graphical representations linking the variations of x, v and a with time.


Appreciation that the
v − t graph is derived from the gradient of the x − t graph and that the a − t graph is derived from the gradient of the v − t graph.
 

Maximum speed = 2p fA
 

Maximum acceleration = 2pf2A

Further Mechanics 4

3.6.1.3 Simple harmonic systems

3.6.1.4 Forced vibrations and resonance

Study of mass-spring system:


Study of simple pendulum:

 


Questions may involve other harmonic oscillators (e.g. liquid in U-tube) but full information will be provided in questions where necessary.


Variation of
Ek , Ep , and total energy with both
displacement and time.


Effects of damping on oscillations.

Further Mechanics 5

(SHM)

 

Further Mechanics 6

(Energy)

 

Further Mechanics 7

(SHM and Circular Motion)

Qualitative treatment of free and forced vibrations.


Resonance and the effects of damping on the sharpness of resonance.


Examples of these effects in mechanical systems and situations involving stationary waves.

Further Mechanics 3

3.6.2 Thermal physics

3.6.2.1 Thermal energy transfer

3.6.2.2 Ideal gases

Calculations involving transfer of energy.


For a change of temperature:
Q = mc Δ q where c is specific heat capacity.


Calculations including continuous flow.


For a change of state
Q = ml where l is the specific latent heat.

 

Thermal Physics 1

Gas laws as experimental relationships between p, V, T, and the mass of the gas.


Concept of absolute zero of temperature.


Ideal gas equation:
pV = nRT for n moles and pV = NkT for N molecules.
 

Work done = p Δ V
 

Avogadro constant NA , molar gas constant R , Boltzmann constant k

 

Molar mass and molecular mass.
 

Thermal Physics 2

3.6.2.3 Molecular kinetic theory model

Brownian motion as evidence for existence of atoms.
Explanation of relationships between p, V and T in terms of a simple molecular model.


Students should understand that the gas laws are
empirical in nature whereas the kinetic theory model
arises from theory.


Assumptions leading to:

 

 

including derivation of the equation and calculations.
 

A simple algebraic approach involving conservation of momentum is required.


 

Appreciation of how knowledge and understanding of the behaviour of a gas has changed over time.

 

Thermal Physics 3

3.7 Fields and their consequences

3.7.1 Gravitational fields

3.7.1.1 Newtonís law

3.7.1.2 Gravitational field strength

Gravity as a universal attractive force acting between all matter.
 

Magnitude of force between point masses:

 


where
G is the gravitational constant.


Students should recognise that the force is a vector the direction of which must be determined by inspection.

Fields 1

Concept of a force field as a region in which a body
experiences a force. Representation by gravitational field lines.


g as force per unit mass as defined by:

 


 

Magnitude of g in a radial field given by:

 

Fields 1

3.7.1.3 Gravitational Potential

3.7.1.4 Orbits of planets and satellites

Understanding of definition of gravitational potential,
including zero value at infinity.


Understanding of gravitational potential difference.


Work done in moving mass
m given by ΔW = mΔV
 

Equipotential surfaces.


Idea that no work is done when moving along an
equipotential surface.


V in a radial field given by:

 

 
 

Significance of the negative sign.


Graphical representations of variations of
g and V with r.


V related to g by:

 


Δ V from area under graph of g against r.

Fields 2

Orbital period and speed related to radius of circular orbit;
 

derivation of T2 r3


Energy considerations for an orbiting satellite.


Total energy of an orbiting satellite.


Escape velocity.


Synchronous orbits.


Use of satellites in low orbits and geostationary orbits, to include plane and radius of geostationary orbit.

 

Fields 3

3.7.2 Electric fields

3.7.2.1 Coulombís law

3.7.2.2 Electric potential

Force between point charges in a vacuum:
 


 

Permittivity of free space, e0.


Appreciation that air can be treated as a vacuum when calculating force between charges.
 

For a charged sphere, charge may be considered to be at the centre.
 

Representation of electric fields by electric field lines.
 

Electric field strength.
 

E as force per unit charge defined by:

 


 

Magnitude of E in a uniform field given by:

 


 

Derivation from work done moving charge between plates:


Fd = EQ


Trajectory of moving charged particle entering a uniform electric field initially at right angles.
Magnitude of
E in a radial field given by:

 

Fields 4

 

Understanding of definition of absolute electric potential, including zero value at infinity, and of electric potential
difference.

 

Work done in moving charge Q given by

Δ W = Q Δ V


Equipotential surfaces.
 

No work done moving charge along an equipotential surface.


Magnitude of
V in a radial field given by:

 


 

Graphical representations of variations of E and V with r.


V related to E by


ΔV from the area under graph of E against r.

 

Fields 5

3.7.2.3 Comparison of electric and gravitational fields

Similarities: inverse square law fields having many characteristics in common.


Differences: masses always attract but charges may attract or repel.


Comparison of magnitude of these forces between subatomic particles.

Quantum Physics 4

Fields 5

3.7.3 Capacitance

3.7.3.1 Capacitance

3.7.3.2 Parallel Plate Capacitor

Definition of capacitance:

 

Capacitors 1

Dielectric action in a capacitor:

 


 

Relative permittivity and dielectric constant.
 

Students should be able to describe the action of a simple polar molecule that rotates in the presence of an electric field.

Capacitors 3

3.7.3.3 Energy stored by a capacitor

3.7.3.4  Capacitor Charge and Discharge

Interpretation of the area under a graph of charge against pd.

 

 

Waves 3

 

Capacitors 1

 

Graphical representation of charging and discharging of capacitors through resistors.

 

Corresponding graphs for Q,
V and I against time for charging and discharging.
 

Interpretation of gradients and areas under graphs where appropriate.


Time constant
RC.


Calculation of time constants including their determination from graphical data.


Time to halve:


 

Quantitative treatment of capacitor discharge:

 


 

Use of the corresponding equations for V and I.
 

Quantitative treatment of capacitor charge:


Capacitors 2

3.7.4 Magnetic fields

3.7.4.1 Magnetic flux density

3.7.4.2 Moving charges in a magnetic field

Force on charged particles moving in a magnetic field,  F = BQv when the field is perpendicular to velocity.


Direction of force on positive and negative charged
particles.


Circular path of particles; application in devices such as the cyclotron.

Magnetic Fields 1

(Magnetism)

 

Magnetic Fields 2

(Coils)

 

Magnetic Fields 3

(Particles)

Magnetic flux defined by F = BA where B is normal to A.


Flux linkage as
NF where N is the number of turns
cutting the flux.


Flux and flux linkage passing through a rectangular coil rotated in a magnetic field:


Magnetic Fields 4

3.7.4.4 Electromagnetic induction

3.7.4.5 Alternating currents

Simple experimental phenomena.


Faradayís and Lenzís laws.


Magnitude of induced emf = rate of change of flux linkage

 

Applications such as a straight conductor moving in a magnetic field.

 

Emf induced in a coil rotating uniformly in a magnetic field:
 

Magnetic Fields 5

(Induction)

 

Magnetic Fields 6

(Generators)

 

 

Sinusoidal voltages and currents only; root mean square, peak and peak-to-peak values for sinusoidal waveforms only.
 

 

Application to the calculation of mains electricity peak and peak-to-peak voltage values.


Use of an oscilloscope as a dc and ac voltmeter, to
measure time intervals and frequencies, and to display ac waveforms.


No details of the structure of the instrument are required but familiarity with the operation of the controls is expected.

Electricity 9

(AC)

 

Electricity 10

(CRO)

3.7.4.6 The operation of a transformer

The transformer equation:

 



 

Production of eddy currents.


Causes of inefficiencies in a transformer.


Transmission of electrical power at high voltage including calculations of power loss in transmission lines.

Magnetic Fields 7

(Transformers)

 

Magnetic Fields 8

(Transmission of Electricity)

3.8 Nuclear physics

3.8.1 Radioactivity

3.8.1.1 Rutherford scattering

3.8.1.2 α , β and γ radiation

Qualitative study of Rutherford scattering.
 

Appreciation of how knowledge and understanding of the structure of the nucleus has changed over time.

Nuclear Physics 2

Their properties and experimental identification using simple absorption experiments; applications e.g. to relative hazards of exposure to humans.


Applications also include thickness measurements of
aluminium foil paper and steel.


Inverse-square law for γ radiation:

 


Experimental verification of inverse-square law.
 

Applications, e.g. to safe handling of radioactive sources.
 

Background radiation; examples of its origins and
experimental elimination from calculations.


Appreciation of balance between risk and benefits in the uses of radiation in medicine.

Nuclear Physics 1

(Radiation)

 

Nuclear Physics 4

(Inverse Square Law)

3.8.1.3 Radioactive decay

3.8.1.4 Nuclear instability

Random nature of radioactive decay; constant decay
probability of a given nucleus:

 


 

Use of activity:


Modelling with constant decay probability.
 

Questions may be set which require students to use
 


Questions may also involve use of molar mass or the
Avogadro constant.


Half-life equation:

 


Determination of half-life from graphical decay data
including decay curves and log graphs.

 

Applications e.g. relevance to storage of radioactive waste, radioactive dating, etc.
 

Nuclear Physics 5

Graph of N against Z for stable nuclei.

Possible decay modes of unstable nuclei including α, β+, β−, and electron capture.

Changes in
N and Z caused by radioactive decay and representation in simple decay equations.

Questions may use nuclear energy level diagrams.

Existence of nuclear excited states; γ ray emission;
application e.g. use of technetium-99m as a γ source in medical diagnosis.
 

 

Nuclear Physics 3

 

3.8.1.5 Nuclear radius

3.8.1.6 Mass and energy

Estimate of radius from closest approach of alpha particles and determination of radius from electron diffraction.

Knowledge of typical values for nuclear radius.


Students will need to be familiar with the Coulomb
equation for the closest approach estimate.

Dependence of radius on nucleon number:


 

derived from experimental data.


Interpretation of equation as evidence for constant density of nuclear material.


Calculation of nuclear density.


Students should be familiar with the graph of intensity against angle for electron diffraction by a nucleus.

Nuclear Physics 6

Appreciation that:

 

applies to all energy changes.

 

Simple calculations involving mass difference and binding energy.


Atomic mass unit, u.


Conversion of units;1 u = 931.5 MeV.


Fission and fusion processes.


Simple calculations from nuclear masses of energy
released in fission and fusion reactions.


Graph of average binding energy per nucleon against nucleon number.


Students may be expected to identify, on the plot, the regions where nuclei will release energy when undergoing fission/fusion.


Appreciation that knowledge of the physics of nuclear energy allows society to use science to inform decision making.

Nuclear Physics 7

3.8.1.7 Induced fission

3.8.1.8 Safety aspects

Fission induced by thermal neutrons; possibility of a chain reaction; critical mass.
 

The functions of the moderator, control rods, and coolant in a thermal nuclear reactor.
 

Details of particular reactors are not required.
 

Students should have studied a simple mechanical model of moderation by elastic collisions.
 

Factors affecting the choice of materials for the moderator, control rods and coolant. Examples of materials used for these functions.

Nuclear Physics 8

Fuel used, remote handling of fuel, shielding, emergency shut-down.


Production, remote handling, and storage of radioactive waste materials.


Appreciation of balance between risk and benefits in the development of nuclear power.

Nuclear Physics 8

 

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Periodic Motion   Thermal Physics   Gravity Fields    Electric Fields   Capacitors   Magnetic Fields    Radioactivity