Chapter 7: Static Charge is produced by electron transfer.
Electrostatics Kit
Why must there be contact between the
two objects to produce a charge?
 How can the charged object lift the tiny
pieces of paper off the table?

Static Charge

Also known as static electricity is electric
charge that is collected and held in one
place. (not moving)
Atom – Positive & Negative
All matter is made up of tiny particles
called atoms.
 Atoms are made up fo a nucleus which
contains neutrons (neutral charge) and
protons (positive charge).
 Around the nucleus are much lighter
particles called electrons (negative
charge).

Model of an Atom
Charge

How can an object become charged?

Adding or removing electrons
 When electrons are added to an object it
becomes negatively charged.
 When electrons are removed from an object
it becomes positively charged.
Simulation

http://phet.colorado.edu/en/simulation/b
alloons
Activity 7-1B

Complete Activity 7 -1 B, p. 231
Insulators & Conductors

Insulator
 Materials that do not allow charges to move
easily within the material.
○ Ex: Plastic, Rubber
Can an insulator become charged?
 What happens to the charge on an
insulator?

Conductors

Materials that allow electrons to travel
freely.
 Ex: Metals, Water

What happens when a conductor
becomes charged?

Can you identify the conductors &
insulators in a wire?
Checkpoint!

One of these isolated charged spheres is
copper and the other is rubber. The diagram
below shows how the charge is distributed.
Label which is copper and which is rubber
and support your answer with an
explanation.
Measuring Charge
A neutral object has the same number of
electrons and positive.
 A charged object has more electrons
than protons if it is negatively charged
and more protons than electrons if it is
positively charged.
 How do we measure the charge?

Coulomb
Unit of charge is called the coulomb (C)
named after Charles Coulomb.
 1 C of charge = 6250000000000000000
electrons removed or added.
 A lightning bolt has a charge between 5
to 25 C.

Van de Graff Generator

http://www.youtube.com/watch?v=sy05B
32XTYY&safety_mode=true&persist_saf
ety_mode=1&safe=active
Grounding
Objects with an excess of charge either positive or negative - can have
this charge removed by a process
known as grounding.
 Grounding is the process of removing
the excess charge on an object by
means of the transfer of electrons
between it and another object of
substantial size. (usually the earth)

Why?

When an oil tanker car has arrived at its
destination, it prepares to empty its fuel into
a reservoir or tank. Part of the preparation
involves connecting the body of the tanker
car with a metal wire to the ground. Suggest
a reason for why is this done.
Check your Understanding

P. 237 #2, 3, 5, 6, 7, 10, 14, 15, 16
Electric Force
Force is defined as a push or pull.
 An electric force is an action-at–adistance force which can apply force to
an object without touching it.

Laws of Static Charge
1. Opposite Charges Attract
 http://www.mrwaynesclass.com/teacher/elec
trostatics/demos/home.html
2. Like Charges Repel
3. Neutral Objects are attracted to charged
objects.
http://www.mrwaynesclass.com/teacher/el
ectrostatics/ceiling/home.html
Laws of Static Charge

Charles Coulomb discovered the laws
and also discovered that:
 If you increase the amount of
charge you increase the amount of force.
 If you increase the distance
between charged objects, you
decrease the electric force.
Charging by Conduction

Charging by conduction involves the
contact of a charged object to a neutral
object.
Charging by Conduction

When charging something by contact it
is important to note the following
properties:
1. The objects must actually touch and transfer
some electrons.
2. The objects become charged alike.
3. The original charged object becomes less
charged because it actually lost some
charge. Therefore, there is a limit to how
many times it could be used to charge
something without being recharged.
Charging by Induction
A neutral object is charged by bringing a
charged object close to but do not touch
the object.
 The neutral object becomes charged
where the charged object was brought
near.
 The object has a whole remains neutral.

Photocopier

Read p. 241.