1. INTRODUCTION TO
ELECTROSTATICS

2. What is Electrostatics?

The study of charges at rest.
Origin of Electricity: started with
the observation of the unusual
behavior of amber and lodestone.
 Lodestone --- a magnetized iron
ore
 Amber ---- translucent yellowishbrown fossil resin
*(amber is “elektron” in Greek,
hence the word electricity)


3. Theories on Charges
1. One Fluid Theory by Benjamin Franklin
- suggests that all bodies possess a certain amount
of “electric fluid” needed to keep them uncharged
2. Two Fluid Theory by Charles Du Fay
- suggest that all bodies contain equal amounts of 2
kinds of fluids
3. Dielectric Theory by Maxwell and Faraday
- considers charges as a form of strain in the
hypothetical ether surrounding a body
4. Electron Theory
- explains the existence of charges by the structure
of an atom

4. The Atomic Structure: A Review



Neutron ------ uncharged
Protons ------- positive
charge
Electron ------ negative
charge
* An atom is uncharged or
neutral if it has equal
number of protons and
electrons.
* An atom becomes
negatively charged
(ANION) if it gains
additional electrons (more
electrons than protons),
* An atom becomes positively
charged (CATION) if it
loses electrons (more
protons than electrons).

5. Electric Charges

A fundamental property of
some particles which could
either be negative or positive.
COULOMB’s LAW
 Rule of Charges


LIKE CHARGES REPEL
UNLIKE CHARGES ATTRACT

6. Material Types Based on Electrical
Conductivity
Conductor
-a material which has plenty of free (valence) electrons
which readily allow charges to flow
Insulator
- a material that resists the flow of charges
Semiconductor
- an intermediate group of materials between conductors
and insulators which can act either as an insulator or
conductor depending on specific orientation and/or
conditions
Superconductor
- a material that offers practically no resistance to the
flow of charges below some critical temperatures

7. Electrostatic Charging
- a process by which an insulator or an insulated
conductor receives a net charge; it involves a neutral
body and a charged (positive or negative) body

8. Methods of Electrostatic Charging
1. Charging by Conduction
- charging in which there is actual contact between
the neutral body and the charged body
a. charging by friction
- done by rubbing a neutral material with cloth or fur,
electrons are then transferred making the body
charged
b. charging by contact
- done by placing the neutral body into contact with a
charge body; charges will then be conducted into the
neutral body

9. The Triboelectric Series – a list that ranks various
materials according to their tendency to gain or lose
electrons.
Most Positive (+)
Steel
Air
Wood
Human Hands, Skin
Sealing Wax
Rabbit Fur
Amber
Glass
Human Hair
Nylon
Wool
Lead
Cat Fur
Silk
-
Rubber Balloon
Hard Rubber
Nickel
Copper
Silver
Brass
Synthetic Rubber
Gold, Platinum
Aluminum
Sulfur
Paper
Teflon
Cotton
Most Negative
---

10. Methods of Electrostatic Charging
2. Charging by Induction
- charging that does not involve contact between the
neutral body (body to be charge) and the charge
body
- this is done by placing both bodies close together;
polarization then occurs in the neutral body; by
grounding the neutral body (touching it with a third
body) charges will flow into the neutral body thereby
charging it

11. Methods of Electrostatic Charging
What is Polarization
 The realignment or separation of charges in one
body when another body, that is charged, is placed
close to it.

12. 
fin

13. Quantization of Charge




The SI unit of charge is the Coulomb ( C ).
The charge of one electron is q = -1.6 x 10-19 C ;
the charge of one proton is
q = +1.6 x 10-19 C.
.
Since a body is charged either by gaining or losing
electrons, it follows that the charge of a body must be
integral multiples of the charge of one electron (or
proton). And the smallest charge of a particle must the be
1.6 x 10-19 C.
OPERATIONAL DEFINITION
q = n x (1.6 x 10-19 C)
where: q is the total charge of n electrons
n is the number of electrons

14. BASIC Examples
1. An object is to have a charge of 1.0 C. How many
electrons are involved in the process? Are the
electrons removed or given to the object?
2. A comb rubbed on the hair several times acquires a
net charge of -0.96 C. Did the comb gain or lose
electrons? How many electrons were transferred?

15. Ohm’s Law
And the basics of CIRCUITS

16. The Concept of Potential Difference

POTENTIAL DIFFERENCE
- the work done or energy needed in moving a unit
electric charge between two points in an electric field

Sources of Potential Difference
1. electric cells – uses chemical energy
2. generators – uses mechanical energy
3. solar cells (or photovoltaic cells) – uses light
energy

17. EMF vs.Voltage



Electromotive Force (emf)
- the potential difference between the terminals of a
cell when no current flows
Terminal Voltage (or simply voltage, V) or J/C
- the potential difference between the terminals of a
cell when current flows
Since a cell has an internal resistance that requires
energy (or potential difference) to overcome, then
the terminal voltage is always less than the
electromotive force.
( V < emf )

18. Current and Resistance

ELECTRIC CURRENT ( I )
- amount of charge passing through any point in a
conductor per unit time
I = q / t unit: C/s or ampere (A); 1C/s = 1A

RESISTANCE ( R )
- the opposition a material offers to the flow of
charges
through it
- the SI unit of resistance is ohm (Ω) or J.s / C2
- named after George Simon Ohm

19. OHM’s LAW

it states that in an electric circuit; the current (I) passing through a
conductor varies directly as the potential difference (V) applied at its
ends and inversely as the resistance (R) of the conductor; this
maybe applied to the entire circuit or to a particular part of a circuit
OPERATIONAL DEFINITION
for the whole circuit:
IT = VT / RT
for a portion of the circuit:
I=V/R
Units: I --- amperes (A); 1A = 1C/s
V – volt (V)
R – ohm (Ω)

20. Example (Ohm’s Law)
A typical value of the resistance of a person from hand
to hand through the body is 2000 Ω. If a person with
this resistance accidentally touches a 220V live wire,
what current passes through the person?

21. Simple Circuits



SERIES CIRCUIT
a simple circuit that contains
more than one piece of
electrical apparatus (or
resistors) connected one
after the other in a single
line
in this circuit, the current
flows in a single path and is
the same in all parts; and
the current stops flowing
whenever a part of the
circuit fails

22. Simple Circuits



PARALLEL CIRCUIT
a simple circuit where two or more pieces of electrical apparatus (or
resistors) are connected side by side so that the current is divided
between them
in this circuit, each apparatus operates independently of the others
so even if one piece fails, current still flows through the others