1.1.1 Atoms have a nucleus containing protons and neutrons. Electrons move
around the nucleus of an atom. An atom has the same number of protons and
electrons, so the + and - charges balance and the atom has no overall charge.
1.1.2 Insulating materials can be given an electrostatic charge by rubbing
two materials together. Electrons are transferred from one material to
another. The material that has gained electrons has a negative
charge. The material that has lost electrons has a positive charge
equal in size to the negative charge.
1.1.3 A charged object (such as a plastic comb) can attract uncharged objects (such
as small pieces of paper). This happens because the comb induces a charge
in the pieces of paper.
1.2 USES AND DANGERS
1.2.1 If you feel a shock by becoming in contact with an object, electrons are
moving to "cancel out" the charge on you. This is called earthing.
Lightning happens when a charge of static electricity builds up in clouds.
When the charge is big enough, charged particles can flow through the
air. The energy released by this causes light and sound. Lightning can kill
living things and damage buildings.
1.2.2 INSECTICIDE SPRAYERS - nozzle of the sprayer is connected to the electricity
supply. Then the droplets all get a static charge. Then the droplets repel each other
so the spray spreads out evenly.
1.2.3 PAINT SPRAYING - the nozzle of the paint sprayer is connected to the electricity supply. Then the droplets
get a static charge so they spread out evenly. Then the object being painted is given the opposite charge to
the paint. The paint is attracted to the object being painted and less paint is wasted.
1.2.4 Static electricity can build up on a plane as it flies. When it is being refuelled, the static charge
may cause a spark when the nozzle of a fuel tanker touches the plane. This could cause an
explosion if it ignited fuel vapour. A conducting wire called a bonding line is used to earth any
static charge on the plan before refuelling starts. Electrons can flow along the wire to earth to
neutralise the static charge on the plane.
1.3 ELECTRIC CURRENTS
1.3.1 An electric current in a wire is a flow of electrons.
The current supplied by cells and batteries is direct
1.3.2 The size of a current is a measure of how much
charge flows past a point each second. It is the
rate of flow of charged particles. CHARGE =
CURRENT X TIME
1.4 CURRENT AND VOLTAGE
1.4.1 The current in an electric circuit is measured using
an ammeter. The ammeter is placed in a circuit in
series with the other components. The voltage is
measured using a voltmeter. The voltmeter is placed
in parallel with the component.
1.4.2 The current in a series circuit is the same. A
parallel circuit has more than one path for
current to flow through. The current splits up
when it reaches a junction and comes back
together when the wires re-join.
1.5 RESISTANCE, CURRENT AND VOLTAGE
1.5.1 The resistance of a component is a way of measuring how hard it is for
electricity to flow through it. The higher the resistance, the smaller the
current. The resistance of a circuit can be changed by putting different
resistors into the circuit.
1.6 CHANGING RESISTANCES
1.6.1 FILAMENT LAMPS - get hotter as the voltage increases.
This increases their resistance. The higher the temperature,
the higher the resistance.
1.6.2 DIODES - when the current flows in one direction, diodes behave like fixed resistors. The
resistance does not change if the voltage changes. Diodes only conduct electricity in one
1.6.3 LIGHT-DEPENDENT RESISTORS - the resistances of these is large in the dark. The
resistance gets less if light shines on it. The brighter the light, the lower the resistance.
1.6.4 THERMISTORS - the resistance of these depends
on its temperature. The higher the temperature, the
lower the resistance.
1.7 TRANSFERRING ENERGY
1.7.1 Energy is transferred to a resistor when a current flows through it. The
energy transfer heats the resistor. The heating effect is useful in electric
1.7.2 The POWER of an appliance is the energy transferred
per second. Electrical power = current x potential
1.7.3 The total ENERGY transferred by an appliance
depends on its power and how long it is switched on
for. Energy transferred = current x potential difference x
2 TOPIC 2
2.1 VECTORS AND VELOCITY
2.1.1 Some quantities are vectors. They have a direction as well as
size. Vectors include displacement, velocity, force and
2.1.2 A distance - time graph shows us a particular journey. The
line sloping shows that they are moving. The horizontal line
shows that they are stationary. Speed = distance/time.
2.2 VELOCITY AND ACCELERATION
2.2.1 Acceleration is a change in velocity and its a
vector quantity. Acceleration = change in
2.2.2 This velocity-time graph shows how the velocity of a
train along a straight track changes with time. When
the velocity is at 0, the train is stationary. The sloping
line shows that the train is accelerating.
2.3 RESULTANT FORCES
2.3.1 A force is a vector quantity, because it has a direction as well as a
size. A free-body force diagram represents all the forces on a
single body. Larger forces are shown using longer arrows.
2.3.2 ACTION REACTION FORCES - two touching objects exert forces on each
other, e.g. the force from the foot on the ball is the action force. The ball exerts
an equal opposite reaction force on the boot.
2.4 FORCES AND ACCELERATION
2.4.1 The acceleration produced by a resultant force depends on the size of the
force and the mass of the object. The greater the force, the greater the
acceleration. The greater the mass, the smaller the acceleration. Force =
mass x acceleration.
2.5 TERMINAL VELOCITY
2.5.1 Mass is the amount of matter in an object, and is measured in
kg. Weight is the force of gravity on an object and is measured in
Newtons. On Earth, every kg of mass is pulled down with a force
of 10N. Weight = mass x gravitational field strength.
2.5.2 The force of gravity on a large mass is greater than on a small mass, but
the large mass also needs a greater force to accelerate it.
2.6.2 Factors that affect stopping
distance = mass of vehicle,
speed, reaction time
2.7 MOMENTUM AND SAFETY
2.7.1 The momentum of a moving object
depends on its mass and its velocity. It is
a vector quantity. Momentum = mass x
2.7.2 When two objects collide, the total
momentum before the collision is the
same as the total momentum after the
collision. Momentum is conserved.
2.7.3 Bubble wrap is used to protect
fragile items. if something hits
the wrapped object the air in
the bubbles squashes and
reduces the force on the
2.7.4 Seat belts stretch and slow
you down gradually. When
you slow down gradually, the
rate of momentum is less and
so there are smaller forces on
you, and you are less likely to
2.8 WORK AND POWER
2.8.1 Work is the amount of energy transferred. Work =
force x distance. Power is the rate of doing work.
Power = work done/time taken.
2.9 POTENTIAL AND KINETIC ENERGY
2.9.1 Gravitational potential energy is the energy
stored in an object because it is in a high
position. Gravitational potential energy =
mass x 10N/kg x vertical height
2.9.2 Kinetic energy is the energy stored in
moving objects. Kinetic energy = 0.5 x
mass x velocity squared
2.9.3 CONSERVATION OF ENERGY - energy cannot be
created or destroyed. It can only be transferred from one
form to another.
2.10 BRAKING AND ENERGY CALCULATIONS
2.10.1 A force is needed to make an object change speed. Force =
change in momentum/time
3 TOPIC 3
3.1.1 Atoms of a particular element always have the same
number of protons, but different numbers of neutrons,
3.2 IONISING RADIATION
3.2.1 Some elements are radioactive. Their nuclei is unstable: alpha particle is a
helium nucleus and has an electrical charge. A beta particle is an electron, and
has an electrical charge. Gamma radiation is a form of electromagnetic radiation.
3.2.2 Alpha particles = very ionising. Can be stopped by paper.
Beta particles = moderately ionising. Can be stopped by
aluminium. Gamma rays = weakly ionising. Need thick lead to
3.3 NUCLEUR REACTIONS
3.3.1 In a fission reaction, a large unstable nucleus
splits into two smaller ones, e.g. uranium-235
nucleus splits up when it absorbs a neutron.
The fission of uranium-235 produces 2 daughter
nuclei, two or more neutrons, and releases
3.3.2 A chain reaction is when the neutrons released by the fission of U-235
are absorbed by other nuclei, and each of these nuclei undergo fission,
and produce more neutrons. A chain reaction can be controlled by using
a different material to absorb some of the neutrons. This slows the
reaction as there are fewer neutrons.
3.4 NUCLEAR POWER
3.4.1 Nuclear power stations use nuclear fuels such as uranium-235. The fuel is made
into fuel rods. A reactor core is made of a material called a moderator. Fuel rods
and control rods fit into holes in the moderator. The moderator and control rods
help to control the chain reaction.
3.4.2 The control rods absorb neutrons. If the control rods are pushed down the core,
more neutrons are absorbed and the chain reaction slows down. The neutrons
produced by fission reactions are moving fast. The moderator slows them down so
they are more likely to be absorbed by another U-35 nucleus and cause another
3.4.3 Thermal energy released by the chain reaction is used to turn
water into steam. The steam makes a turbine spin, and the
turbine drives a generator. The daughter nuclei produced in the
fission reaction are radioactive. They neutrons passing through
the core can produce other radioactive isotopes. This radioactive
waste must be disposed of safely.
3.5.1 Nuclear fusion happens
when small nuclei join to
form larger ones. Fusion
reactions release energy.
Isotopes of hydrogen
combine in the Sun to form
helium. The energy
released by these reactions
makes the Sun shine.
3.5.2 Nuclei need to get close to each other
before fusion can happen. The high
temperatures and pressures needed are
difficult to produce is a fusion reaction.
3.6 NUCLEAR WASTE
3.6.1 Three types of waste: high level waste, intermediate level waste and low level waste.
3.6.2 Waste can be disposed of by firing it into space, and
dumped at sea.
3.7 USES OF RADIATION
3.7.1 We are always exposed
to background radiation,
e.g. radon is produced
when uranium decays.
Radon can be built up in
houses and buildings.
3.7.2 Radiation is used in hospitals to
kill cancer cell, diagnose cancer
and sterilize surgical
instruments. Gamma rays make
food safer to eat.
3.7.3 Other uses of radiation are used
to find leaks in pipes, to control
thickness, and smoke alarms.