• All matter is made up of atoms.
• Centre of each atom is a heavy nucleus.
• Surrounding the nucleus is a lot of empty space
and tiny particles called electrons (which are
• Each electron carries a negative electric charge.
• Inside the nucleus are two different particles –
protons and neutrons.
• Protons are much heavier than electrons and
they carry a positive electric charge.
• Neutrons have a similar mass to protons but
carry no electric charge.
The positive electric charge of a proton exactly
balances the negative charge of an electron.
Atoms contain an equal number of electrons
• Any particle or substance that has more
protons than electrons is said to be positively
• More electrons than protons is said to be
• Equal amounts of positive and negative charge
is said to be neutral.
• Is the build up of electric charge on a surface.
• Commonly occurs because of two surfaces
rubbing against each other.
The electrons are rubbed off one surface –
charging is positive – and are transferred to the
other surface – charging it negative.
• Power from batteries and power points is
made up of electrons moving along a wire –
• The energy from the moving electrons is
transformed into other forms of energy such
as heat and movement.
• Electric Current – when charge flows (measured
using a ammeter).
• Unit used to measure current is ampere/amps (A).
• Voltage – measure of the amount of energy
supplied and used by the charges.
• Unit used to measure voltage is volts (V).
• Supply Voltage – Australia 240V
• Some household items use transformers.
• A step-down transformer reduces 240V to the
amount required by an appliance.
• Portable electrical energy.
• Wet Cell – two electrodes placed in a liquid
electrolyte i.e. conducts electricity.
• Dry Cell – used in torches, toys etc. don’t leak
because they use paste instead of liquid.
• Photovoltaic Cells – solar cell.
• Resistance – when electrons pass along wires
their path is restricted by the atoms that make
up the wires.
• A measure of how difficult it is for an electric
current to flow.
Conductors and Insulators
• Conductors - materials with little
resistance to the flow of electric charge
(e.g. copper wires used in most electric
• Little energy is needed for electric charge
to flow through conductors.
• Most metals are very good conductors of
• Insulators - materials with a lot of resistance
to the flow of electric charge
• Allow very little or no electric current through
e.g. air, rubber and plastic.
Circuit diagrams are universal so they can be
used all over the world.
• A string of Christmas tree lights are all connected
to the same power supply.
• If you remove a single light the rest of the lights
will go off.
• This is because the lights are connected in series.
The ceiling lights in most homes need to be
connected together so that if one light globe or
tube stops working, the others remain on – this
requires a parallel circuit.