Static Electricity notes for S4 Biruni.

1. CHAPTER 14
Static Electricity
© 2013 Marshall Cavendish International (Singapore) Private Limited

2. 14.1 Electrostatics
14.2 Electric Field
Chapter 14 Electrostatics

3. Learning Outcomes
At the end of this section, you should be able to:
• state that there are positive and negative charges,
and that charge is measured in coulombs (C);
• state that like charges repel and unlike charges
attract.
14.1 Electrostatics

4. 14.1 Electrostatics
What are Electric Charges?
• Matter is made up of atoms.
• Atoms are made of __________, _________ and
___________.
• If electrons are
_________, the atom
becomes positively
charged.
• If electrons are
_______, the atom
becomes negatively
charged.
• If the numbers of electrons and protons are
_______, the atom is in the neutral state.

5. 14.1 Electrostatics
How do Positive and Negative
Charges Interact?
• Like charges _______
++
+ –
• Unlike charges _________

6. 14.1 Electrostatics
Measuring Electric Charges
• The SI unit of electric charge is the _________
(___).
• The amount of charge carried by an electron is
______________.
• In other words, there are
1 C
1.6 × 10–19 C
= _______________ electrons
in 1 C of charge!

7. 14.1 Electrostatics
14.2 Electric Field
Chapter 14 Electrostatics

8. Learning Outcomes
At the end of this section, you should be able to:
• state what an electric field is;
• draw electric field patterns.
14.2 Electric Field

9. 14.3 Electric Field
Previously, when we rubbed a balloon against a
person’s hair, we observed that the hair was
attracted to the balloon. There were
____________ forces between them.
negatively-charged
balloon
positively-charged
hair
If both objects had the same charge, there would
be a ___________ force pushing the two objects
away from each other.
Recall

10. 14.2 Electric Field
• The force experienced by the charges is an
________________.
• The force is experienced _________ the charges
being in contact with each other.
• The region in which a charge experiences a force
is called the ________________.
An electric force is the ____________ or ___________
force that electric charges exert on one another.
An electric field is a ________ in which an electric
charge experiences an _______________.

11. 14.2 Electric Field
Representing Electric Fields
• An electric field can be illustrated with
– electric field lines, and
– arrowheads to indicate the direction of the
electric field.
The ___________ of an electric field is the direction
of the force that would act on a small __________
charge.

12. F
F
14.2 Electric Field
Representing Electric Fields
If you place small positive test charges around
a positive charge, what would happen?
+
+
F
+ F
+
+
Electric field lines
of a positive charge

13. 14.2 Electric Field
Representing Electric Fields
The __________ of an electric field is indicated by
how _______ the field lines are to one another.
• The electric field lines here
are _________________.
• This indicates that the
electric field in this region is
________.
• The electric field lines here
are ________ together.
• This indicates that the
electric field in this region is
_________.

14. 14.2 Electric Field
Worked Example
How would the field lines of two positive charges
placed close together look?
Solution

15. 14.2 Electric Field
Representing Electric Fields
Electric field lines of parallel plates
• The electric field lines start
from the
____________________
plate and end at the
negatively-charged plate.
• The field is _________ near
the middle of the plates.

16. Chapter 14 Static Electricity
Static Electricity
Static charges
(SI unit: C)
Positive and
negative
charges
is the study of
can be
categorised into
set up Electric
fields
can be
represented by
Electric field lines
• directed away from
a positive charge
• directed towards a
negative charge
interact
as
follows:
• Like charges
repel
• Unlike charges
attract