Static Electricity
Unit 3: Physics - Electricity
Lesson 1
Do not copy
• Staticy clothing and electric
shocks felt when touching
doorknobs on are caused by
electric charges.
Electric Charges
• Electric charges are charged
particles that exert an electric
force on each other.
– (Do not copy) Charged particles are
very small but when they are present
in large enough quantities they can
produce sparks just large enough to
feel or large enough to kill.
Electrically Charged
Particles (Review)
• An element is a pure substance
that cannot be broken down into
simpler substances.
• An element is made up of tiny
particles called atoms.
•
Electrically
Charged
Particles
Within an atom, there are three
types of smaller particles:
– Protons have a positive electric
charge (+) p+
– Electrons have a negative electric
charge (–). e– Neutrons have no electric charge,
they are neutral. n0
Electrically Charged
Particles
• The protons and neutrons are in
the nucleus at the centre of the
atom.
• The electrons are outside the
nucleus
• Atoms are neutral. The number of
protons in the nucleus equals the
number of electrons around the
nucleus. This makes an atom neutral.
• If an atom does not have an equal
number of protons and electrons,
it has an electric charge.
– Electric charge – A form of
charge, either positive or
negative, that exerts an electric
force.
Types of charges on
objects
• Neutral Object – an object that has
equal numbers of protons and
electrons
• Negatively charged object – an object
that has more electrons than protons
• Positively charged object – an object
that has fewer electrons than protons.
Static Charges
• Objects can become charged
when electrons move from one
object to another.
• The electric charge that builds up
on the surface of the object is
called a static charge or static
electricity.
Static Charges
• The charges are “static” because
they remain very nearly fixed in
one location on the surface of
the object until they are given a
path to escape
• Electrostatics is the study of
electric charges
Friction and the
Movement of
Electrons
Friction
• All solid materials are charged by
the transfer of electrons.
– One common cause of electron
transfer is friction.
Friction
• Friction is the force resisting the
relative motion of two surfaces in
contact.
• The force of friction can remove
electrons from one object and
cause them to transfer to the
other object.
Friction
• As one object loses electrons, the
other object gains them.
• The total number electrons
remains the same, they are
transferred from one surface to
another.
• Positive Charges do not move.
(don’t copy)
• For any charging procedure, it’s
important to keep in mind that new
electric charges are not being
created. The electrons in each
object are just being rearranged
within the object or transferred to
another object.
Electron Affinity and the
Electrostatic Series
• Different substances have
different abilities to hold on to
electrons. The tendency of a
substance to hold on to the
electrons is called electron
affinity.
Electron Affinity and the
Electrostatic Series
• The electrostatic series lists a
series of selected materials in
order of their electron affinity.
• The higher the material is in the
list, the greater the tendency for
that material to lose electrons.
Copy Table
Electron Affinity
• The table on the left is
known as a triboelectric
series or the electrostatic
series
• Tribo in Greek means to
rub
Electron Affinity
• This allows one to
determine what charge a
material will have if it is
rubbed against another
material on the table.
Do not copy
• There can be a slightly different
order for materials such as fur or
wood depending on which type of
animal the fur is from and which
type of tree the wood is from
Laws of Attraction and
Repulsion
Law of attraction.
• Particles with opposite charges
attract each other.
Law of Repulsion
• Objects that have the same charges
Repel each other
note
• when a charged object is brought
near a neutral object it will attract
it.
Questions
• 1. Where are electrons in the atom? K
(1)
• 2. What does “static” mean in “static
electricity”?.
• 3. What happens when two objects
made out of different materials are
rubbed together?
• 4. What term describes an atom’s
tendency to hold on to electrons? K (1)
Questions
• 5. In each of the following pairs, state which
one is more likely to give up electrons? I (3)
• (a) wood or human hair
• (b) plastic wrap or steel
• (c) cotton or silk.
• 6. (a) What does the law of attraction state?
• (b) What does the law of repulsion state? K
(2)