Physics CAIE Course code 5054
Specification
Static Electricity
Electric charge
identify common materials which are electrical conductors or insulators, including
metals and plastics
Describe experiments to investigate how insulating materials can be charged by friction
Explain that positive and negative electrostatic charges are
produced on materials by the loss and gain of electrons
Understand that there are forces of attraction between unlike charges and forces of
repulsion between like charges
Explain electrostatic phenomena in terms of the movement of
electrons
Explain the potential dangers of electrostatic charges, eg when fuelling aircraft and
tankers
Explain some uses of electrostatic charges, eg in photocopiers and inkjet printers.
Electrical conductors and insulators
An electrical conductor Complete the table below:
is a material through
which electric current copper conductor
flows easily. rubber insulator
1
All metals are
conductors. steel conductor
2
mercury conductor
3
Electrical insulators
have a very high
paper insulator
resistance to the flow of plastic insulator
4
electric current.
diamond insulator
5
graphite conductor
6
Electric charge
Electric charge can be either
positive or negative.
In an atom an electron has a
negative charge that is of the
same size as the positive
charge of a proton.
Neutrons have no electric
charge.
As an atom has the same
number of electrons as protons
it is uncharged.
Static and current electricity
Static electricity describes the situation
when electric charges remain stationary.
This occurs best with insulators.
An electric current occurs when electric
charges are moving from one place to
another.
This occurs best with conductors.
Charging materials using friction
When certain insulating materials are rubbed against each
other they become electrically charged.
Electrons are rubbed off one material onto the other.
The material that gains electrons becomes negatively
charged.
The material that loses electrons is left with an equal
positive charge.
Force and charge
When a charged object is brought close to an
uncharged one the two objects attract each other.
The charged comb
Charged balloon
attracts the column of
attracted to a wall
water
Attraction and repulsion
Two bodies that carry different
types of charge attract.
Two bodies that carry the same
type of charge repel.
The law of charges:
LIKE CHARGES REPEL,
UNLIKE ATTRACT.
This boy’s hair has all the
same type of charge!
Choose appropriate words to fill in the gaps below:
Static electricity occurs when electric ________
charge remains
____________
stationary on an object.
An __________
insulating object can be charged by __________
rubbing it with
another insulator. One of them gains ________
electrons and becomes
negatively charged. The other becomes equally __________
positively
charged.
The law of charges states that; ‘like charges _______,
repel unlike
_________’.
attract
WORD SELECTION:
attract insulating electrons repel stationary
rubbing positively charge
Hazards of static electricity
The main danger of static
electricity is in situations
where a spark can cause a
fire or an explosion.
The Buncefield oil depot
explosion (opposite) in
December 2005 was
thought to have been
caused by a spark.
Fuel pipe problems
When oil or petrol is fuel pipe connected to earth
pumped along pipes a
static charge can build
up on the pipe which
could result in a spark.
This could cause an
explosion when the fuel
vapour reacts with
oxygen in the air.
Antistatic floors
In operating theatres it is
important that the doctors to
do not become statically
charged when walking
around.
This is because some of the
anaesthetic gases used are
explosive.
Antistatic material is used
for the floor surface so that
any charge is conducted to
earth.
Uses of static electricity:
1. Paint spraying
The spray nozzle is connected is
connected to the positive terminal of
an electrostatic generator.
As the paint droplets leave they
repel each other and spread out to
form a fine cloud of paint.
The metal panel to be painted is
connected to the negative terminal.
The negatively charged metal panel
attracts the positively charged paint.
2. Ink-jet Printer
Spots of ink are given an electric
charge as they leave the ink nozzle.
The deflecting plates cause the
drops to hit the right part of the
paper.
The charges on the deflecting
plates change many times per
second so that each drop hits the
paper in a different position.
INK JET PRINTER
3. Photocopier
4. Smoke precipitator
An electrostatic precipitator is used
to prevent the dust and ash
produced by coal fired power
stations from entering the
atmosphere.
The ash and dust becomes charged
as it passes through the charged
grid of wires.
The ash and dust is then attracted to
the oppositely charged metal plates.
When the plates are shaken the
accumulated ash and dust falls
down to be collected and removed.
Electric Charge
1. Explain how a material can become charged using friction.
2. Describe a simple experiment to show that like charges repel
and unlike charges attract .
3. Explain with the aid of diagrams how the following devices
make use of static electricity: (a) paint sprayers; (b) ink-jet
printers; (c) photocopiers.
4. Describe some of the problems caused by static electricity .
