The Electrostatic Series Of Some Common Substances
Material
Tendency for atoms to
attract electrons
Tends to become
Rubber
High
Negative
Low
Positive
Polyethylene
Ebonite
Cotton
Sulphur
Wood
Silk
Wool
Glass
Acetate
Cat’s fur
1. If the following pairs of objects are rubbed together, what type of electric charge
results on each object?
a) A cat rubs up against a rubber boot.
b) A wool jacket is brushed off with a polyethylene brush.
c) A wooden coffee table is dusted clean with a dry cotton cloth.
d) An acetate overhead transparency is wiped off with a cotton cloth.
2. A glass rod is suspended on an insulating string and is rubbed with a piece of silk.
a) After rubbing, what type of charge is on each material?
b) What should happen if the silk is brought close to the glass rod?
c) Use the electron theory of electricity to explain your answers to (a) and (b).
Charging by Conduction

Charge by Conduction  transferring an electric charge from one substance to another
by touching.

Charging by contact causes electric discharge (sparks/shocks).

Sparks produced by contact can be responsible for fires and
explosions.

Precautions may be necessary to avoid the occurrence of shocks:
o
e.g.: Clothing work by medical professionals and hydro
workers is woven with special fibres designed to eliminate sparks caused by
static electricity.

When charging by contact occurs, one object is already electrically charged.

The other object may or may not be charged or be neutral - the important factor is that
there is a difference in the charge between the two objects.
Charging by Induction

Charge by Induction  the process by which an object having an electric charge
produces the opposite charge in a neighbouring object without actually touching it.

Using this principle, it is possible to determine electrical charges using an instrument
called an electroscope.

Two types of induction:
 Temporary: the induction of charge only occurs due to the presence of a charged
object.
 Permanent: the object in question can be charged from neutral to positive or
negative by grounding the electroscope.
Charging by Conduction
On the following diagrams:
1) Draw in the location of the negative charges
2) Show the direction of the movement of the negative charges
3) Shade in the position of the moveable leaf
Charging by Induction
On the following diagrams:
1) Draw in the location of the negative charges
2) Show the direction of the movement of the negative charges
3) Shade in the position of the moveable leaf