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:
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
|