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Some helpful revision notes for Oxford International AQA examinations - International GCSE Physics 9203 specification - for the AQA IGCSE physics syllabus specification

IGCSE AQA biology 9201

IGCSE AQA chemistry 9202

IGCSE science 9204

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Indexes to help links for all GCSE and IGCSE science courses

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Oxford International AQA examinations - International GCSE Physics 9203 specification (Oxford AQA IGCSE Physics syllabus)


Energy resources, energy transfers, work done & electrical power supply

Revision help notes for Oxford International AQA examinations - International GCSE Physics 9203 specification (Oxford AQA IGCSE Physics)

Types of energy & stores - examples compared/explained, calculations of mechanical work done & power

Chemical energy stores  * Elastic potential energy stores and calculations 

Electrical & electrostatic energy stores  *  Gravitational potential energy and calculations 

Kinetic energy stores and calculations  *  Nuclear energy store

Thermal energy stores  *  Light energy  * Sound energy  * Magnetic energy stores

Conservation of energy, energy transfers-conversions, efficiency - calculations and Sankey diagrams

See also Methods of reducing heat transfer eg in a house, insulating properties of materials

Energy resources: uses, survey, trends, comparing renewables, non-renewables, generating electricity

Renewable energy (1) Wind power and solar power, advantages and disadvantages

Renewable energy (2) Hydroelectric power and geothermal power, advantages and disadvantages

Renewable energy (3) Wave power and tidal barrage power, advantages and disadvantages

See also Renewable energy - biomass - biofuels & alternative fuels, hydrogen, biogas, biodiesel

Greenhouse effect, global warming, climate change, carbon footprint from fossil fuel burning

Absorption & emission of radiation - temperature & surface factors including global warming

The Usefulness of Electricity

and The 'National Grid' power supply, mention of small scale supplies, transformers


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Heat Transfer: Explaining physical changes & physical properties using particle models

Revision help notes for Oxford International AQA examinations - International GCSE Physics 9203 specification (Oxford AQA IGCSE Physics)

Much of this is to do with thermal energy ('heat') transfers from one store to another

Introduction to heat transfer - conduction (and thermal conductivity), convection and radiation

Specific heat capacity: how to determine it, use of data, calculations and thermal energy stores

Energy transfer and efficiency - calculations and Sankey diagrams

More on reducing heat transfer eg in a house and investigating insulating properties of materials

Particle theory models: gases, liquid, solid, internal energy, heat transfer in state changes, latent heat

The density of materials (including measurements) and the particle model of matter


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Electricity and magnetism revision notes index

Revision help notes for Oxford International AQA examinations - International GCSE Physics 9203 specification (Oxford AQA IGCSE Physics)

1. Usefulness of electricity, safety, energy transfer, cost & power calculations, P = IV = I2R, E = Pt, E=IVt

2. Electrical circuits and how to draw them, circuit symbols, parallel circuits and series circuits explained

3. Ohm's Law, experimental investigations of resistance, I-V graphs, calculations V = IR, Q = It, E = QV

4. Circuit devices and how are they used? (e.g. thermistor, LDR, diode), relevant graphs

5. More on series and parallel circuits, circuit diagrams, measurements and calculations

6. The 'National Grid' power supply, environmental issues, use of transformers

7. Comparison of methods of generating electricity

8. Static electricity and electric fields, uses and dangers of static electricity

9. Magnetism - magnetic materials - temporary (induced) and permanent magnets - uses

10. Electromagnetism, solenoid coils, uses of electromagnets

11. Motor effect of an electric current, electric motor, loudspeaker, Fleming's left-hand rule, F = BIL

12. Generator effect, applications e.g. generators generating electricity and microphone


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States of matter, state changes and gas laws revision notes index

Revision help notes for Oxford International AQA examinations - International GCSE Physics 9203 specification (Oxford AQA IGCSE Physics)

Particle models of gases–liquids–solids, explaining properties, state changes (GCSE chemistry notes)

Particle theory models, internal energy, heat transfer in state changes and latent heat and particle motion in gases and gas pressure (written more from a 'physics' point of view)

P-V-T pressure-volume-temperature gas laws and calculations (revision notes for physicists or chemists!)

The density of materials and the particle model of matter


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WAVES - electromagnetic radiation, sound, optics-lenses, light & astronomy

Revision help notes for Oxford International AQA examinations - International GCSE Physics 9203 specification (Oxford AQA IGCSE Physics)

General introduction to the types and properties of waves, ripple tank expts, how to do wave calculations

Illuminated & self-luminous objects, reflection visible light, ray box experiments, ray diagrams, mirror uses

Refraction and diffraction, the visible light spectrum, prism investigations, ray diagrams explained

Electromagnetic spectrum, sources, types, properties, uses (including medical) and dangers

Absorption & emission of radiation by materials - temperature & surface factors including global warming

See also Global warming, climate change, reducing our carbon footprint from fossil fuel burning

Optics - types of lenses (convex, concave, uses), experiments and ray diagrams, correction of eye defects

The visible spectrum of colour, light filters and explaining the colour of objects

Sound waves, properties explained, speed measure, uses of sound, ultrasound, infrasound, earthquakes

The Structure of the Earth, crust, mantle, core and earthquake waves (seismic wave analysis)

Astronomy - solar system, stars, galaxies and use of telescopes and satellites

The life cycle of stars - mainly worked out from emitted electromagnetic radiation

Cosmology - the Big Bang Theory of the Universe, the red-shift & microwave background radiation


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Atomic structure, radioactivity, ionising radiation - properties and uses

Revision help notes for Oxford International AQA examinations - International GCSE Physics 9203 specification (Oxford AQA IGCSE Physics)

0. Atomic structure, history, definitions, examples and explanations including isotopes

1. Atomic structure and fundamental particle knowledge needed to understand radioactivity

2. What is Radioactivity? Why does it happen? Three types of atomic-nuclear-ionising radiation

3. Detection of radioactivity, its measurement and radiation dose units, ionising radiation sources - radioactive materials, background radiation

4. Alpha, beta & gamma radiation - properties of 3 types of radioactive nuclear emission & symbols ,dangers of radioactive emissions - health and safety issues and ionising radiation

5. Uses of radioactive isotopes emitting alpha, beta (+/–) or gamma radiation in industry and medicine

6. The half-life of a radioisotope - how long does material remain radioactive? implications!, uses of decay data and half-life values - archaeological radiocarbon dating, dating ancient rocks

7. What actually happens to the nucleus in alpha and beta radioactive decay and why? nuclear equations!, the production of radioisotopes - artificial sources of radioactive-isotopes, cyclotron

8. Nuclear fusion reactions and the formation of 'heavy elements' by bombardment techniques

9. Nuclear Fission Reactions, nuclear power as an energy resource


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Forces

Revision help notes for Oxford International AQA examinations - International GCSE Physics 9203 specification (Oxford AQA IGCSE Physics)

1. What are contact forces & non-contact forces?, scalar & vector quantities, free body force diagrams

2. Mass and the effect of gravity force on it - weight, (mention of work done, GPE and circular motion)

3. Calculating resultant forces using vector diagrams and work done calculations

4. Elasticity and energy stored in a spring

5. Turning forces & moments - spanners to wheelbarrows, levers, gears & equilibrium situations

6. Pressure in liquid fluids and hydraulic systems

7. Pressure & upthrust in liquids, why do objects float/sink?, variation of atmospheric pressure with height


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Motion and associated forces (including Newton's Laws of Motion)

Revision help notes for Oxford International AQA examinations - International GCSE Physics 9203 specification (Oxford AQA IGCSE Physics)

1. Speed and velocity - the relationship between distance and time, distance-time graphs

2. Acceleration, velocity-time graph interpretation and calculations, problem solving

3. Acceleration, friction, drag effects and terminal velocity experiments

4. Newton's First, Second and Third Laws of Motion, inertia and F = ma calculations

5. Reaction times, stopping distances, safety aspects. calculations including F=ma

6. Elastic and non-elastic collisions, momentum calculations and Newton's 2nd law of motion


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Indexes to help links for all GCSE and IGCSE science courses

Oxford AQA International GCSE Physics

Full syllabus for OxfordAQA IGCSE Physics specification 9203

PHYSICS (Oxford AQA International GCSE Physics)

FORCES AND THEIR EFFECTS (Oxford AQA International GCSE Physics)

This topic explores the interactions (forces) between objects that can change their shape or the way they are moving. Mathematical relationships can predict the resultant motion of an object and applications illustrate how forces can be used to achieve certain outcomes and avoid others.

Forces and their interactions (Oxford AQA International GCSE Physics)

a. Objects interact by non-contact (field) forces (including gravity, electrostatics, magnetism) and by contact forces (including friction, air resistance, tension and normal contact force).
b. Friction is a force between two surfaces, which impedes motion and may result in heating. Air resistance is a form of friction.
c. Pairs of objects interact to produce a force on each other, which can be represented as vectors.
d. Scalars are quantities that have magnitude only. Vectors are quantities that have direction as well as a magnitude. A vector quantity may be represented by an arrow. The length of the arrow represents the magnitude and the direction of the arrow represents the direction of the vector quantity.
Students should be aware that distance, speed and time are examples of scalars and displacement, velocity, acceleration, force and momentum are examples of vectors.
e. Weight is the force acting on an object due to gravity. The weight of an object depends on the gravitational filed strength at the point where the object is. The weight of an object can be calculated using the equation:
Weight (N) = mass (kg) × gravitational field strength (N/kg)
W = m × g
Students will not be expected to know the value of g; it will be given in any examination items.
f. When more than one force is applied to an object they may cause a change in the shape of the object, by stretching, bending or compressing. After elastic distortions an object returns to its original shape when the forces are removed. After inelastic distortions an object does not return to its original shape.

g. A force applied to an elastic object such as a spring will result in the object stretching and storing elastic potential energy.
h. For an object behaving elastically, the extension is directly proportional to the force applied, provided that the limit of proportionality is not exceeded. The relationship between the force, F, and the extension, e, is: F = k × e  (where k is a constant).
Required practical:
Investigate the relationship between force and extension for a spring

Motion (Oxford AQA International GCSE Physics)

a. If an object moves in a straight line, its distance from a certain point can be represented by a distance–time graph.
b. The speed of the object can be calculated from the gradient of a distance–time graph.
c. The velocity, v, of an object is its speed in a given direction and is given by the equation: v = s / t where s is the displacement (distance) and t is the time taken.
d. This equation can also be used to calculate the average speed of objects undergoing non-uniform motion.

Resultant forces (Oxford AQA International GCSE Physics)

a. Whenever two objects interact, the forces they exert on each other are equal in magnitude and opposite in direction. This is Newton’s Third Law.
b. A number of forces acting on an object may be replaced by a single force that has the same effect on the motion as all the original forces acting together. This single force is called the resultant force.
Students should be able to determine the resultant of opposite or parallel forces acting in a straight line and determine the resultant of two coplanar forces by scale drawing.
c. A non-zero resultant force acting on an object causes it to accelerate.
d. Acceleration is the rate of change of velocity. An object can accelerate by changing its direction even if it is going at a constant speed. Deceleration is a negative acceleration. The average acceleration, a, of an object is given by the equation:
     a = ∆v / t  (where v is the change in velocity and t is the time taken for the object to accelerate)
e. The acceleration of an object can be calculated from the gradient of the velocity–time graph.
f. The distance travelled by an object can be calculated from the area under a velocity–time graph.
g. If the resultant force acting on an object is zero:
a moving object will continue to move at the same velocity
a stationary object will remain at rest.
This is Newton’s First Law.
h. If the resultant force on an object is not zero, the object will accelerate in the direction of the resultant force. The relationship between the resultant force, F, acting on an object, its mass, m, and the acceleration caused, a, is: F = m x a
This is Newton’s Second Law.

Motion (Oxford AQA International GCSE Physics)

a. If an object moves in a straight line, its distance from a certain point can be represented by a distance–time graph.
b. The speed of the object can be calculated from the gradient of a distance–time graph.
c. The velocity, v, of an object is its speed in a given direction and is given by the equation: v = s / t where s is the displacement (distance) and t is the time taken.
d. This equation can also be used to calculate the average speed of objects undergoing non-uniform motion.

MOMENTUM (Oxford AQA International GCSE Physics)
a. All moving objects have momentum. The relationship between momentum, p, mass, m, and velocity, v, is:
   p = m × v
b. In a closed system the total momentum before an interaction is equal to the total momentum after the interaction. This is called conservation of momentum.
Students may be required to complete calculations involving two objects. Examples of interactions are collisions and explosions.
c. The relationship between force, F, change in momentum, ∆p, and time, t, is:
  F =  ∆p / t
ie the force equals the rate of change of momentum.
Students should be able to use this relationship to explain qualitatively car safety features such as air bags, seat belts, side impact bars, crumple zones. Also, gymnasium crash mats, cushioned surfaces for playgrounds and cycle helmets.

Safety in public transport (Oxford AQA International GCSE Physics)

a. When a vehicle travels at a steady speed in a straight line the resistive forces are balancing the driving force.
b. The greater the speed of a vehicle the greater the braking force needed to stop it in a certain distance. The greater the braking force the greater the deceleration of the vehicle. Large decelerations may lead to brakes overheating and/or loss of control.
Students should understand that, for a given braking force, the greater the speed, the greater the stopping distance.
c. The stopping distance of a vehicle is the sum of the distance the vehicle travels during the driver’s reaction time (thinking distance) and the distance it travels under the braking force (braking distance). A driver’s reaction time can be affected by tiredness, distractions, drugs and alcohol.
d. When the brakes of a vehicle are applied, work done by the friction force between the brakes and the wheel reduces the kinetic energy of the vehicle and the temperature of the brakes increases.
e. A vehicle’s braking distance can be affected by adverse road and weather conditions and poor condition of the vehicle.
Students should understand that ‘adverse road conditions’ includes wet or icy conditions. Poor condition of the car is limited to the car’s brakes or tyres.

FORCES AND TERMINAL VELOCITY (Oxford AQA International GCSE Physics)
a. An object moving through a fluid experiences friction. The faster the object moves, the greater the frictional forces (drag) acting on it.
b. An object falling through a fluid will initially accelerate due to the force of gravity and the drag forces increase as the velocity increases. Eventually the resultant force will be zero and the object will move at its terminal velocity.
c. Parachutes are designed to increase the drag force on a parachutist so that the terminal velocity is reduced.

Students should be able to draw and interpret velocity–time graphs for objects that reach terminal velocity, including a consideration of the forces acting on the object.
d. Streamlining reduces the drag force on an object so that its maximum velocity is increased.
Students should be able to describe how the streamlining of a shark (an adaptation) or a car (a design feature) reduces the drag force and the object

CENTRE OF MASS (Oxford AQA International GCSE Physics)
a. The centre of mass of an object is the point at which the mass of the object may be thought to be concentrated.
Students will be expected to be able to describe how to find the centre of mass of a thin lamina with irregular shape.
b. If freely suspended, an object will come to rest with its centre of mass directly below the point of suspension.
c. The centre of mass of a symmetrical object is along the axis of symmetry. The position of the centre of mass affects the stability of objects

MOMENTS AND LEVERS (Oxford AQA International GCSE Physics)
a. The turning effect of a force is called the moment. The relationship between the moment, M, turning force, F, and perpendicular distance, d, from the point where the force is applied to the pivot is:
  M = F x d
b. If an object is not turning, the total clockwise moment must be exactly balanced by the total anticlockwise moment about any pivot.
Students should be able to calculate the size of a force, or its distance from a pivot, acting on an object that is balanced.
c. If the line of action of the weight of an object lies outside the base of the object there will be a resultant moment and the body will topple.
Examples should include vehicles and simple balancing toys.
d. Simple levers can be used as force multipliers.

ENERGY (Oxford AQA International GCSE Physics)

This topic starts with the principles of energy transfer and then explores it in various contexts, such as heating. It considers the idea that energy is never destroyed but may end up so dissipated that it is of little use.

Forces and energy (Oxford AQA International GCSE Physics)

a. Work is done when a force causes an object to move through a distance. The relationship between work done, W, force, F, and distance, d, moved in the direction of the force is: W = F x d
b. Energy is transferred when work is done. Work done against frictional forces causes energy transfer by heating.
Students should be able to discuss the transfer of kinetic energy in particular situations, for example shuttle re-entry into the atmosphere or meteorites burning up in the atmosphere and braking systems on vehicles.

c. The amount of elastic potential energy stored in a stretched spring (assuming the limit of proportionality has not been exceeded) can be calculated using the equation:  Ee = ½ × k × e2   (E = stored energy, k = spring constant, e = spring extension, watch the units)

d. An object gains gravitational potential energy when it is raised vertically because work is done against the gravitational force. The relationship between gravitational potential energy, Ep , mass, m, gravitational field strength, g, and height, h, is:
   Ep = m × g × h
e. The kinetic energy of a moving object depends on its mass and its velocity. The relationship between kinetic energy, Ek , mass, m and velocity, v, is: Ek = ½ × m × V2

Students should understand that when the mass of an object is doubled, if it is travelling at the same speed it will have twice the kinetic energy. They should understand that an object travelling at twice the speed of another object with the same mass will have four times the kinetic energy and should be able to apply this idea in the context of road safety.
f. Power is the rate at which energy is transferred or the rate at which work is done. The relationship between power, P, work done, W, or energy transferred, E, and time, t, is: P = E / t  and  P = W / t (and watch the units, J, s and W, 1W = 1J/s)
 

Energy transfers, conservation and dissipation of energy (Oxford AQA International GCSE Physics)

a. When a system changes, energy is transferred. A system is an object or group of objects.
Students should be able to identify when and where energy has been transferred using concepts such as kinetic energy, gravitational potential energy and elastic potential energy.

b. A simple pendulum is an example of oscillating motion and energy is transferred between kinetic energy and gravitational potential energy.
c. Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.
d. When energy is transferred only part of it may be usefully transferred; the rest is dissipated so that it is stored in less useful ways. This energy is often described as being ‘wasted’.
e. Friction and air resistance are forces that dissipate energy by heating the surroundings.
f. The efficiency of a device can be calculated using: % efficiency = 100 x (useful energy out) / (total energy in)
   and also % efficiency = (useful power out) / (total power in) (× 100 %)
Students may be required to calculate efficiency as a decimal or as a percentage.
g. The energy flow in a system can be represented using Sankey diagrams.
Students should be able to draw and interpret Sankey diagrams to show how the overall energy in a system is redistributed when the system is changed but there is no net change to the total energy

Energy resources (Oxford AQA International GCSE Physics)

a. Fuels are a useful store of energy; different fuels are suitable for different situations and are selected according to a range of factors, such as ease of storage, energy content and safety.
b. When a fuel is used, some energy is transferred to the surroundings. Some fuels are more efficient than others.
c. There is a range of energy sources used on a national and global scale. Their use has implications for society in terms of factors including renewability and the environmental impacts of extraction, use and disposal.
d. A range of technologies have been developed to provide energy in a renewable way, such as wave power, solar power and geothermal power.
Students should be aware of these and other examples and be able to identify advantages and drawbacks with their use.

WAVES (Oxford AQA International GCSE Physics)

Waves, both transverse and longitudinal, carry energy from a source and can be detected by a receiver. This topic explores the properties of waves and their application to contexts such as information communication and sight.
 

General properties of waves (Oxford AQA International GCSE Physics)

a. A wave is a disturbance caused by an oscillating source that transfers energy and information in the direction of wave travel, without transferring matter.
b. In a transverse wave the oscillations are perpendicular to the direction of energy transfer.
c. In a longitudinal wave the oscillations are parallel to the direction of energy transfer. Longitudinal waves have areas of compression and rarefaction.
d. Electromagnetic waves and water waves are transverse, sound waves are longitudinal and mechanical waves may be either transverse or longitudinal.
e. Waves can be reflected, transmitted or absorbed (or a combination of these) at the boundary between two different materials.
f. Waves can undergo refraction due to a change in speed and diffraction through a narrow gap or at an edge.
Students should appreciate that for appreciable diffraction to take place the wavelength of the wave has to be comparable to the size of the obstacle or gap.

Students may be required to apply these ideas to the reduction of diffraction in optical instruments, ultrasound waves in medicine and radio wave reception.
Required practical:
Investigate the refraction of light in glass blocks.
g. Wave motion can be described in terms of their frequency, wavelength, period, amplitude and wavefront.
Students should be able to explain the meaning of these terms.
h. The relationship between wave speed, v, frequency, f, and wavelength, λ, is: v = f × λ

The electromagnetic spectrum (Oxford AQA International GCSE Physics)

a. Electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber.
b. Electromagnetic waves form a continuous spectrum and all types of electromagnetic wave travel at the same speed through a vacuum (space).
Students should know the order of electromagnetic waves within the spectrum, grouped in terms of energy, frequency and wavelength. They should appreciate that the wavelengths of the electromagnetic spectrum range from 10–15 m to 104 m and beyond.
c. Visible light is the part of the electromagnetic spectrum that is detected by our eyes; we see different wavelengths as different colours.
d. d. All objects emit and absorb infrared radiation. [Objects emit infrared radiation because of the motion of their particles. The amount and frequency of emitted radiation depends on the temperature and surface of the object ]. The hotter an object is the more infrared radiation it radiates in a given time..
Dark, matt surfaces are good absorbers and good emitters of infrared radiation.
Light, shiny surfaces are poor absorbers and poor emitters of infrared radiation.
Light, shiny surfaces are good reflectors of infrared radiation.
e. As an object heats up it radiates more and more infrared and radiation at higher frequencies.
f. Black-body radiation is the range of electromagnetic radiation emitted by an object at a particular temperature.

g. Radio waves, microwaves, infrared and visible light can be used for communication.
h. Electromagnetic waves have many practical applications. For example:
radio waves – television and radio systems (including Bluetooth)
microwaves – mobile phones and satellite television systems
infrared – TV remote controls, night vision devices, heating
visible light – photography, fibre optic communications
ultraviolet – security marking
X-rays – medical imaging
gamma rays – sterilising surgical instruments and killing harmful bacteria in food.
i. Excessive exposure of the human body to electromagnetic waves can be hazardous. Low energy waves have a heating effect and higher energy waves have enough energy to cause ionisation (remove an electron from an atom or molecule). For example:
microwaves – heating of body tissue
infrared – skin burns
ultraviolet – skin cancer and blindness
X-rays – high doses kill cells
gamma rays – genetic mutations.
Students should be able to describe simple protection measures against risks.
j. X-rays are part of the electromagnetic spectrum. They have a very short wavelength, high energy and cause ionisation

k. Properties of X-rays include:
they affect a photographic film in the same way as light
they are absorbed strongly by metal and bone
they are transmitted by healthy tissue.
l. X-rays can be used to diagnose some medical conditions, for example in computed tomography (CT) scanning, bone fractures and dental problems. X-rays are also used to treat some conditions, for example in killing cancer cells.
m. The use of high energy ionising radiation can be dangerous, and precautions need to be taken to monitor and minimise the levels of radiation that people who work with it are exposed to.

Sound and Ultrasound (Oxford AQA International GCSE Physics)

a. Sound waves are longitudinal waves and cause vibrations in a medium, which are detected as sound. The range of human hearing is about 20 Hz to 20 000 Hz.
No details of the structure of the ear are required.
b. The pitch of a sound is determined by the frequency of vibrations of the source. Its loudness is related to the size of the amplitude of the disturbance.
c. Sound waves can be reflected (echoes) and diffracted.

d. Ultrasound is acoustic (sound) energy, in the form of waves with a frequency above the human hearing range.
e. Electronic systems can be used to produce ultrasound waves, which have a frequency higher than the upper limit of hearing for humans.
f. Ultrasound waves are partially reflected when they meet a boundary between two different media. The time taken for the reflections to reach a detector can be used to determine how far away such a boundary is.

g. The distance, s, between interfaces in various media can be calculated using: P
  s = v x t  (where v is wave speed and t is time taken).
Students may be required to use and interpret data from diagrams of oscilloscope traces.
h. Ultrasound waves can be used in medicine. Examples include prenatal scanning and the removal of kidney stones.

Reflection (Oxford AQA International GCSE Physics)

a. When waves are reflected the angle of incidence is equal to the angle of reflection.
b. The normal is a construction line perpendicular to the reflecting surface at the point of incidence.
c. The image produced in a plane mirror is virtual, upright and laterally inverted.
Students will be expected to be able to construct ray diagrams to represent the changing path of reflected rays.

REFRACTION AND TOTAL INTERNAL REFLECTION (Oxford AQA International GCSE Physics)
a. The velocity of waves is affected by the medium they are travelling through. The speed changes. Unless the wave enters at 90° to the surface (along the normal) the direction also changes. This is called refraction.
b. Light waves are refracted at an interface:
when light enters a denser medium it is refracted towards the normal
when light enters a less dense medium it is refracted away from the normal.
Students should have the opportunity to use wave front diagrams to explain refraction in terms of the change in speed that happens when a wave travels from one medium to another.
c. Refraction by a prism can lead to dispersion of light waves and the formation of a spectrum.
d. Refractive index can be defined in terms of wave speed.
The refractive index of a medium is defined as:
  speed of light in vacuum (air) / speed of light in the medium
e. The relationship between refractive index, n, angle of incidence, i , and angle of refraction, r, is:
   n = sin i / sin r
Required practical:
Investigate the refraction of light by different substances.
f. The relationship between refractive index, n, and critical angle, c, is:
   n = 1 / sin c
Recall of the values of critical angles is not required.

g. Total internal reflection is a special case of refraction, which occurs if the angle of incidence within the denser medium is greater than the critical angle.
h. Visible light and infra red can be transmitted through optical fibres by total internal reflection.
Students should be able to describe the application and benefits of optical fibres in medicine and communication technology.

LENSES AND THE EYE (Oxford AQA International GCSE Physics)
a. A lens forms an image by refracting light.
b. In a convex (converging) lens, parallel rays of light are brought to a focus at the principal focus.
Students should be aware of the nature of the image produced by a converging lens for an object placed at different distances from the lens, including the use of the converging lens as a magnifying glass.
c. In a concave (diverging) lens, parallel rays of light diverge as if coming from the principal focus.
Students should be aware of the nature of the image produced by a diverging lens for an object placed at
different distances from the lens.
d. The distance from the lens to the principal focus is called the focal length.
e. The nature of an image is defined by its size relative to the object, whether it is upright or inverted relative to the object and whether it is real or virtual.
f. Ray diagrams are used to show the formation of images by convex and concave lenses.
Students may be asked to draw and interpret ray diagrams drawn on graph paper.
g. The magnification produced by a lens may be calculated using the equation:
   magnification = image height / object height
h. Our eyes only detect visible light, a limited range of electromagnetic waves. The eye contains the following structures:
retina
variable focus lens
cornea
pupil/iris
ciliary muscle
suspensory ligaments.
Students should know the function of each of these parts and understand how the action of the ciliary muscle causes changes in the shape of the lens that allow light to be focused arriving from varying distances. They should understand that light entering the eye is refracted by the cornea as well as by the lens.
i. Usually the near point of the human eye is approximately 25 cm from the eye and the far point is at infinity. The eye can focus on objects between the near point and the far point. The distance between these points is called the range of vision

j. Lenses can be used to correct defects of vision:
long sight, caused by the eyeball being too short, or the eye lens being unable to focus a sharp image on the retina
short sight, caused by the eyeball being too long, or the eye lens being unable to focus a sharp image on the retina.
Students should understand the use of convex and concave lenses to rectify these defects and assist the eye to produce a focused image on the retina.
k. Lasers are concentrated sources of light and can be used for cutting, cauterising and burning. Lasers can be used in eye surgery, to correct visual defects.
Knowledge of how lasers work is not required.
l. Comparisons can be made between the structure of the eye and the camera. In the eye the image is brought to focus on the retina by changing the shape of the lens, in a camera the image is brought to focus on the film or CCD sensor by varying the distance between the film and the lens.
Students should be aware that the film (or CCD sensor) in a camera is the equivalent of the retina in the eye

PARTICLE MODEL OF MATTER (Oxford AQA International GCSE Physics)

The properties of materials can be understood in terms of constituent particles, their motions and interactions.

Kinetic theory (Oxford AQA International GCSE Physics)

a. Kinetic theory can be used to explain the different states of matter and their properties. The particles in solids, liquids and gases have different amounts of energy.
Students should be able to recognise, use and compare simple diagrams to represent key features of solids, liquids and gases.
b. The specific heat capacity of a substance is the amount of energy required to change the temperature of one kilogram of the substance by one degree Celsius. The relationship between energy, E, mass, m, specific heat capacity, c, and temperature change, ∆θ, is: E = m × c × θ
c. The specific latent heat of vaporisation of a substance is the amount of energy required to change the state of one kilogram of the substance from a liquid to a vapour with no change in temperature. The relationship between energy, E, mass, m, and specific latent heat of vaporization, LV , is: E = m × LV
d. The specific latent heat of fusion of a substance is the amount of energy required to change the state of one kilogram of the substance from a solid to a liquid with no change in temperature. The relationship between energy, E, mass, m, and specific latent heat of fusion, LF , is: E = m × Lf
e. The melting point of a solid and the boiling point of a liquid are affected by impurities.
Throughout this section, students should be able to explain the shape of the temperature–time graph for a substance that is either cooled or heated through changes in state

Required practical:
Investigate cooling curves for stearic acid.

Energy transfers and particle motion (Oxford AQA International GCSE Physics)

a. Energy may be transferred by conduction and convection.
Students should be able to explain, in terms of particles, how these energy transfers take place. They should understand in simple terms how the arrangement and movement of particles determine whether a material is a conductor or an insulator and understand the role of free electrons in conduction through a metal. They should be able to use the idea of particles moving apart to make a fluid less dense, to explain and apply the concept of convection.
b. Energy may be transferred by evaporation and condensation.
Students should be able to explain evaporation, and the cooling effect this causes, using kinetic theory.
Students should be able to discuss the factors that affect the rate of evaporation.
c. The rate at which an object transfers energy by heating depends on:
its surface area and volume
the material from which the object is made
the nature of the surface with which the object is in contact.

Students should be able to explain the design of devices in terms of energy transfer, for example cooling fins, and should be able to explain animal adaptations in terms of energy transfer, for example relative ear size of animals in cold and warm climates.
d. The bigger the temperature difference between an object and its surroundings, the faster the rate at which energy is transferred by heating.
e. Most substances expand when heated.
Students should understand that the expansion of substances on heating may be a hazard (for example, the expansion of roofs and bridges) or useful (for example, the bi-metallic strip thermostat).

ELECTRICITY AND MAGNETISM (Oxford AQA International GCSE Physics)

Electricity is convenient because it is easily transmitted over distances and can be easily transferred in a range of different ways. By controlling the flow of current and understanding the factors that affect this flow it can be used to make a range of applications work. Electricity is also a good context for considering how energy is transferred. Magnetism provides a connection with forces through the study of fields and the way it can produce and be produced by electricity.

Electrical circuits (Oxford AQA International GCSE Physics)

a. Electrical charges can move easily through some substances; for example metals have many charges (electrons) that are free to move.

b. There may be an imbalance of charge in an object or area; this is known as static electricity. The charge has no conducting route to travel along. If such a route is provided, the result is a discharge.

Students should be aware of some common instances of static electricity, such as lightning, and how they
can be explained using the concepts of charge and discharge.
c. Electric current is the rate of flow of electric charge. Charge flow, Q, current, I, and time, t, are linked by the equation:

  I = Q / t
d. The voltage of a source is the energy supplied by a source in driving charges round a complete circuit and is measured in volts.
e. Potential difference across a component measures the energy transfer by charges and is measured in volts.
f. The relationship between potential difference, V, energy transferred, E, and charge, Q, is: V = E / Q
Teachers can use either of the terms potential difference or voltage. Questions will be set using the term potential difference. Students will gain credit for the correct use of either term.

g. Circuit diagrams use standard symbols.
Students will be required to interpret and draw circuit diagrams. Students should know the following standard symbols:

Students should understand the use of thermistors in circuits, for example thermostats.
Students should understand the use of light-dependent resistors (LDRs) in circuits, for example switching lights on when it gets dark.
h. Components resist the flow of charge through them. The greater the resistance the smaller the current for a given potential difference across the component. The resistance of a component can be found by measuring the current through and potential difference across, the component. The relationship between potential difference, V, current, I, and resistance, R, is: V= I × R
i. The current through a resistor (at a constant temperature) is directly proportional to the potential difference across the resistor. This means that the resistance remains constant as the current changes, graph (1) below.

 

j. The resistance of components such as lamps, diodes, thermistors and LDRs is not constant; it changes with the current through the component.
k. The resistance of a thermistor decreases as the temperature increases.
Students should be able to describe the applications of thermistors in circuits eg a thermostat.
l. The resistance of an LDR decreases as light intensity increases.
Students should be able to describe the applications of LDRs in circuits eg switching lights on when it gets dark.

m. The resistance of a filament lamp increases as the temperature of the filament increases, graph (2) above.

Students should be able to explain change in resistance in terms of ions and electrons.

n. The ‘forward’ resistance is low in a diode and the ‘reverse’ resistance is very high. The current through a diode flows in one direction only. Graph (3) above.

Required practical:
Investigate the V–I characteristics of a filament lamp, a diode and a resistor at constant temperature.
o. An LED emits light when a current flows through it in the forward direction.
Students should be aware that the use of LEDs for lighting is increasing, as they use a much smaller current than other forms of lighting.
p. The combined voltage of several sources in series is their sum.
q. There are two ways of joining electrical components: in series and in parallel. Some circuits include both series and parallel parts.
r. For components connected in series:
the combined resistance is the sum of the resistance of each component
the current is the same in each component
the total potential difference of the power supply is shared between the components.
s. For components connected in parallel:
the combined resistance is less than that of either component
the current from the supply splits in the branches
the potential difference across each component is the same.
t. When an electrical charge flows through a resistor, the resistor gets hot because of collisions between moving charges and stationary atoms in the wire.
Students should understand that a lot of energy is wasted in filament bulbs by heating. Less energy is wasted in power saving lamps such as Compact Fluorescent Lamps (CFLs). They should understand that there is a choice when buying new appliances in how efficiently they transfer energy.

Magnetism and electromagnetism (Oxford AQA International GCSE Physics)

a. Magnetic forces are strongest at the poles of a magnet. When two magnets are brought close together they exert a force on each other. Two like poles repel each other and two unlike poles attract. Attraction and repulsion between two magnetic poles are examples of non-contact forces.
Students should be able to predict the interaction between magnets given their physical arrangement.
b. The space around a magnet where a force acts on another magnet or on a magnetic material (iron, steel, cobalt, nickel) is called a magnetic field. The strength and direction of a magnetic field change from one point to another.
Students should be able to recognise magnetic field patterns using one or two bar magnets. In a uniform magnetic field the lines of the magnetic field are parallel.
c. An induced magnet is a material that becomes a magnet when it is placed in a magnetic field. Induced magnetism always causes a force of attraction. When removed from the magnetic field an induced magnet loses most/all of its magnetism quickly.
Students should be able to explain how a magnet attracts a magnetic object by inducing a magnetic field around it.
d. The earth has a magnetic field that is most concentrated at the magnetic north and south poles.
Students should be able to explain how a plotting compass can be used to detect the earth’s magnetic field and to assist in navigation.
e. A magnetic field is produced when an electric current flows through a wire. The magnetic field lines are concentric circles in a plane, perpendicular to the wire

The field is stronger closer to the wire.
Increasing the current makes the magnetic field stronger.
Reversing the current reverses the direction of the magnetic field lines.
f. Shaping a wire to form a solenoid increases the strength of the magnetic field created by a current through the wire. The magnetic field inside a solenoid is strong and uniform.
g. The magnetic field around a solenoid has a similar shape to that of a bar magnet. Adding an iron core increases the magnetic field strength. An electromagnet consists of a solenoid with an iron core.
Students should be familiar with some typical uses of electromagnets.
Required practical: Investigate the factors that determine the strength of an electromagnet

GENERATING AND DISTRIBUTING ELECTRICITY AND HOUSEHOLD USE

In this topic magnetism and electromagnetism are studied in the context of their uses in using current to cause motion and vice versa and in changing the voltages of an ac supply. In so doing the big ideas of field forces and energy transfer are also used.

GENERATING ELECTRICITY (Oxford AQA International GCSE Physics)
a. A potential difference (pd) is induced across the ends of a conductor when:
the conductor moves relative to a magnetic field
the conductor is in a changing magnetic field.
This is called the generator effect.
Students should be able to suggest the factors that affect the size of the induced pd.
b. A potential difference is induced across the ends of a coil of wire when:
a permanent magnet is moved into or out of the coil
the coil is moved relative to the magnet.
c. If the conductor is part of a complete circuit, a current flows in the wire. The magnetic field produced by the induced current opposes the field of the permanent magnet.
d. If the direction of motion, or the polarity of the magnet, is reversed, the polarity of the induced potential difference and direction of flow of any induced current are reversed.
e. The size of the induced potential difference increases when:
the speed of the movement increases
the strength of the magnetic field increases
the number of turns on the coil increases
the area of the coil increases.
Students should be able to explain how an alternator generates ac and a dynamo generates dc, including graphs of potential difference generated in the coil against time. However, detailed knowledge of slip rings and split rings are not required.
f. Power stations use turbines to turn wire coils between magnets to generate electricity.

ELECTRICITY TRANSMISSION AND DISTRIBUTION (Oxford AQA International GCSE Physics)
a. Electricity is distributed from power stations to consumers along transmission cables with transformers at both ends.
Students should be able to identify and label the essential parts of an electric power transmission and distribution system.
b. For a given power rating, a high distribution voltage reduces the current flowing, therefore reducing energy losses due to heating and making the system more efficient.

c. A basic transformer consists of a primary coil and a secondary coil wound on a soft iron core. An alternating current in the primary coil of a transformer produces a changing magnetic field in the iron core and hence in the secondary coil. This induces a changing potential difference across the ends of the secondary coil and an alternating current flows.
Students should be able to describe the basic structure and operation of a transformer. Knowledge of laminations and eddy currents in the core are not required.
d. Step-up and step-down transformers are used to increase the voltage before the distribution lines and reduce it at the end to produce a safer voltage for local consumers.
In a step-up transformer the potential difference across the secondary coil is greater than the potential difference across the primary coil.
In a step-down transformer the potential difference across the secondary coil is less than the potential difference across the primary coil.
e. The potential differences across the primary and secondary coils of a transformer, Vp and Vs , are related to the number of turns on the coils, np and ns , by:

Vp   np
---- = ----
Vs   ns

f. For a 100% efficient transformer, the electrical power output would equal the electrical power input.
Vp × Ip =  Vs × Is
Where Vp and Ip are power input (primary coil) and Vs and Is are power output (secondary coil).
Students should be aware that the turns ratio is selected to produce the required output from the input

g. Switch mode transformers are transformers that:
operate at a high frequency, often between 50 kHz and 200 kHz
are much lighter and smaller than traditional transformers that work from a 50 Hz mains supply, making them useful for applications such as mobile phone chargers
use very little power when they are switched on but no load is applied

Using electricity in the home (Oxford AQA International GCSE Physics)

a. Cells and batteries supply current that always passes in the same direction. This is called direct current (dc).
b. An alternating current (ac) is one that is repeatedly changing direction.
Students should be able to determine the period, and hence the frequency, of a supply from diagrams.
They should be able to compare and calculate potential differences of dc supplies and the peak potential differences of ac supplies from diagrams.
c. Mains electricity is an ac supply, which has a set frequency and voltage.
Knowledge of root mean square (rms) measurements and values are not required.
d. There are a number of safety features that can be incorporated in electrical systems and appliances. One of these is earthing: if the metal body of an appliance becomes live through a fault, the current is harmlessly conducted away.
e. If an electrical fault causes too great a current to flow, a fuse or a circuit breaker in the live wire disconnects the circuit. The current will cause the fuse wire to overheat and melt or the circuit breaker to switch off (‘trip’). A circuit breaker operates much faster than a fuse and can be reset.
f. Appliances with metal cases are usually earthed. If a fault develops a large current flows from the live wire to earth. This melts the fuse and disconnects the live wire.
Students should be aware that some appliances are double insulated and therefore have no earth wire connection

The motor effect (Oxford AQA International GCSE Physics)

a. A current carrying conductor has a magnetic field around the wire. When a current carrying conductor is placed in a magnetic field so that it cuts lines of magnetic force, the magnet and the conductor exert a force on each other. This is called the motor effect. The conductor will not experience a force if it is parallel to the magnetic field.
b. The size of the force can be increased by:
increasing the strength of the magnetic field
increasing the size of the current
increasing the length of the conductor in the magnetic field.
c. The direction of the force is reversed if either the direction of the current or the direction of the magnetic field is reversed.
Students should be able to identify the direction of the force using Flemings left-hand rule.
d. A coil of wire carrying a current in a magnetic field tends to rotate. This is the basis of an electric motor.

Transferring electrical energy (Oxford AQA International GCSE Physics)

a. Electrical appliances are designed to transfer energy.
Students should be able to give examples of such devices and identify the energy transfers.
b. The rate at which energy is transferred by an appliance is called the power. The relationship between power, P, energy transferred, E, and time, t, is: P = E / t
c. The power transfer, P, in any device is related to the current, I, flowing through it and potential difference, V, across it:

    P = × I V
Students should be able to calculate the current through an appliance from its power and the potential difference of the supply and from this determine the size of fuse needed.
d. The relationship between energy transferred, E, potential difference, V, and charge, Q, is:  E = V × Q
e. The amount of energy an appliance transfers depends on how long the appliance is switched on for and its power rating. It is often more convenient to measure energy transfers in domestic appliances in kWh instead of J due to the small size of the latter.
f. The relationship between energy transferred, E, from the mains, power, P, and time, t, is: E(kWh) = P(kW) x t(h)
Students will not be required to convert between kilowatt-hours and joules.
Students should be able to calculate the cost of mains electricity given the cost per kilowatt-hour and interpret and use electricity meter readings to calculate total cost over a period of time.

NUCLEAR PHYSICS (Oxford AQA International GCSE Physics)

The structure of material is used to model what an atom consists of, what might happen when atoms break apart and when they fuse together. This provides ways of actually or potentially generating power and explains processes at the centre of stars.

Atomic structure (Oxford AQA International GCSE Physics)

The structure of material is used to model what an atom consists of, what might happen when atoms break apart and when they fuse together. This provides ways of actually or potentially generating power and explains processes at the centre of stars.
ATOMIC STRUCTURE
a. Atoms are very small, having a radius of about 10 -10 metres. The simple model of an atom is a small central positively charged nucleus composed of protons and neutrons, surrounded by electrons. The radius of the nucleus is much smaller than that of the atom with almost all of the mass in the nucleus.
b. The scattering of alpha particles by thin metal foil provides evidence of the distribution of mass in the atom.
c. The relative masses and electric charges of protons, neutrons and electrons are as follows:

Sub–atomic particle Relative mass Electric charge Comments
Proton 1 +1 (+ positive) In the nucleus, a nucleon
Neutron 1 0 (zero) In the nucleus, a nucleon
Electron 1/1850 or 0.00055

very small

–1 (– negative) NOT a nucleon. Electrons are arranged in energy levels or shells in orbit around the nucleus

d. In an atom the number of electrons is equal to the number of protons in the nucleus. The atom has no overall electrical charge.
e. In each atom its electrons are arranged at various distances from the nucleus. Atoms may lose or gain outer electrons to form charged particles called ions.
f. The atoms of a particular element always have the same number of protons, but have a different number of neutrons for each isotope. The total number of protons in an atom is called its proton number or atomic number. The total number of protons and neutrons in an atom is called its mass number. Atoms can be represented as shown:
: mass number of 23, atomic number 11 for sodium

Ionizing radiation from the nucleus (Oxford AQA International GCSE Physics)

a. Some atomic nuclei are unstable. The nucleus emits particles or radiation and the nucleus changes to that of a different element and becomes more stable. This is a random process called radioactive decay.
b. Energy is emitted by changes in the nucleus.
c. Unstable nuclei emit alpha particles, beta particles, or neutrons, and electromagnetic radiation as gamma waves. Neither chemical nor physics processes affect this behaviour. These substances are said to be radioactive and although the general process follows a pattern this radioactive decay is a random process. It is impossible to predict when a particular atom might decay.
d. Background radiation is around us all of the time. It comes from a range of sources, such as radioactive substances in the environment, from space or from devices such as X-ray machines in hospitals.
e. An alpha particle consists of two neutrons and two protons (i.e. a Helium nucleus). A beta particle is a high speed electron ejected from the nucleus as a neutron turns into a proton. Gamma radiation is electromagnetic radiation from the nucleus.

f. Nuclear equations are used to represent radioactive decay.
Students will be required to balance equations for single alpha and beta decay, limited to the completion of atomic number and mass number. The identification of daughter elements from such decays is not required.
g. Properties of the alpha, beta and gamma radiations are limited to their relative ionising power, their penetration through materials and their range in air.

h. Radioactive decay is random, but with a large enough number of nuclei it is possible to predict how many will decay in a certain amount of time. The half-life of a radioactive isotope is:
the average time it takes for the number of nuclei of the isotope in a sample to halve
the time it takes for the count rate from a sample containing the isotope to fall to half its initial level.
i. Radioactive contamination is the unwanted presence of radioactive atoms on other materials. The hazard from contamination is due to the decay of the contaminating atoms. The type of radiation emitted affects the level of hazard. Irradiation is the process of exposing an object to ionizing radiation. The irradiated object does not become radioactive. Suitable precautions must be taken to protect against the hazards of the radioactive source used in irradiation.
Students should be able to compare the hazards associated with contamination and irradiation.
j. Radioactive isotopes have a very wide range of half-life values. The most unstable nuclei have the shortest half-lives; decay is rapid with a lot of radiation emitted in a short time. The least unstable nuclei have the longest half-lives; hey emit little radiation each second but emit radiation for a long time. There are uses and dangers associated with each type of nuclear radiation.
Students should be able to evaluate the possible hazards associated with the use of different types of
ionizing radiation and the effect of half-life

Nuclear fission (Oxford AQA International GCSE Physics)

a. Nuclear fission is the splitting of a large and unstable nucleus and the release of energy.

b. There are two fissionable substances in common use in nuclear reactors: uranium-235 and plutonium-239.
Students should be aware that the majority of nuclear reactors use uranium-235.
c. For fission to occur the uranium-235 or plutonium-239 nucleus must first absorb a neutron to make the nucleus unstable. The nucleus undergoing fission splits into two smaller nuclei, releasing two or three neutrons and energy. The amount of energy released during nuclear fission is much greater than that released in a chemical reaction involving a similar mass of material.
d. A chain reaction occurs when neutrons from the fission go on to cause further fission. In a nuclear reactor control rods absorb fission neutrons to ensure that on average only one neutron per fission goes on to produce further fission and energy transfer.
Students should be able to sketch or complete a labelled diagram to illustrate how a chain reaction may occur.
e. Nuclear reactions produce waste which may be dangerous due to its radioactive nature and may remain so for a long time, depending upon its half life and products. The disposal of such waste needs to be managed with care and is a factor that may influence the use of nuclear power for the generation of electricity.

NUCLEAR FUSION (Oxford AQA International GCSE Physics)
a. Nuclear fusion is the joining of two light nuclei to form a heavier nucleus.
b. In this process some of the mass of the smaller nuclei is converted into energy.
c. The force of repulsion between the two positive nuclei must be overcome for them to get close and fuse and this happens at very high temperatures and pressures.
d. Nuclear fusion is the process by which energy is released in stars.

SPACE PHYSICS (Oxford AQA International GCSE Physics)

Space physics uses ideas about forces and motion, energy transfer, atomic structure and fields to develop explanations about the start and end of the universe and about how the Earth receives energy from the Sun. Space was one of the first challenges that civilisation tried to explain in its attempts to account for day, season, year and the appearance of the night sky and remains one of the most challenging due to its scale and complexity.

Life cycle of a star (Oxford AQA International GCSE Physics)

a. Stars form when enough dust and gas (mainly hydrogen and helium) from space are pulled together by gravitational attraction. Smaller masses may form and be attracted by a larger mass to become planets, or even stars.
b. During the ‘main sequence’ period of its life cycle, energy is released by the fusion of hydrogen nuclei to make helium nuclei in the core and a star is stable because the forces within it are balanced. The term ‘radiation pressure’ will not be required.
c. The core (centre) of a star is where the temperature and density are greatest and where most nuclear fusion takes place.
d. The more massive a star, the hotter its core and the heavier the nuclei it can create by fusion.
e. Stars change over time; they have a life cycle. This life cycle is determined by the mass of the star.
f. A main sequence star uses nuclear reactions to produce light and heat. When it runs out of hydrogen, what happens next in its life cycle depends upon its mass.

g. A larger star will swell to become a red supergiant, in which helium nuclei fuse to form carbon, followed by further fusion that produces heavier nuclei such as nitrogen and oxygen. It expands, cools and turns red. The outer layers then blast away as a supernova is formed. The core then collapses and depending upon mass, it forms either a neutron star or a black hole.
h. A smaller star, similar to our Sun, follows a different sequence, expanding to become a red giant. It then sheds out layers of gas, exposing the core as a white dwarf and finally cools to become a black dwarf. Students should be familiar with charts that show the life cycles of stars.
i. Fusion processes in stars are the source of energy and produce all of the naturally occurring elements. These elements may be distributed throughout the universe by the explosion of a massive star (supernova) at the end of its life.
Students should be able to explain how stars are able to maintain their energy output for millions of years, why the early universe contained only hydrogen but now contains a large variety of different elements and that elements heavier than iron are formed in a supernova.

Solar system and orbital motion (Oxford AQA International GCSE Physics)

a. The Earth is one of eight planets orbiting the Sun (a medium sized star), which together with other smaller objects (asteroids, dwarf planets, comets) and moons orbiting several planets, make up the solar system.
Students should be able to describe the principal differences between planets, moons, the Sun, comets and asteroids in terms of relative size and motion.
b. Our universe is made up of:
thousands of millions of galaxies that are each made up of thousands of millions of stars
our Sun is one of thousands of millions of stars in our galaxy called the Milky Way.
c. Planets orbit the Sun and a moon is a natural satellite of a planet. Artificial satellites orbit the Earth and can be in geostationary or low polar orbits.
d. Gravity provides the centripetal force that keeps planets and satellites (both natural and artificial) in orbit.
e. The force of gravity acts towards the centre of the orbit. This unbalanced force causes acceleration towards the centre of the orbit, changing the direction of motion of the body (its velocity) but not its speed. The equation for calculating centripetal force is not required.
f. The centripetal force due to gravity decreases as the separation of orbiting masses increases, resulting in lower orbital speeds.
g. At a particular separation of the masses, the centripetal force results in a particular orbital speed. To stay in a stable orbit at a particular distance, the planet or satellite moves at a particular speed. A change in orbital speed results in a change in orbital radius.
Students should be able to explain the motion of moons and artificial satellites and be able to apply this to the design of satellite placing where the speed will determine the radius of the satellite’s final position

RED SHIFT AND THE EXPANDING UNIVERSE (Oxford AQA International GCSE Physics)
a. If a wave source is moving relative to an observer there will be a change in the observed wavelength and frequency.

This is known as the Doppler effect. Students should understand that:
the wave source could be, for example, light, sound or microwaves
when the source moves away from the observer, the observed wavelength increases and the frequency decreases
when the source moves towards the observer, the observed wavelength decreases and the frequency increases.
b. There is an observed increase in the wavelength of light from most distant galaxies. The further away the galaxies, the faster they are moving and the bigger the observed increase in wavelength. This effect is called red shift. The observed red shift suggests that space itself is expanding and supports the Big Bang model (that the universe began from a very small initial point).
Students should be able to explain how red shift provides evidence for the Big Bang.
c. Cosmic microwave background radiation (CMBR) is a form of electromagnetic radiation filling the universe. It comes from radiation that was present shortly after the beginning of the universe.
d. Scientists believe that the universe began with a ‘big bang’, 14 thousand million years ago. The Big Bang theory is currently the only theory that can explain the existence of CMBR

 

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