Physics Trivia• Lightning is responsible for a number of deaths

and injuries of people and livestock each year. A great percentage of lightning casualties is

caused by standing tall trees during a rain. A person lucky enough to survive lightning strike is

most likely to suffer the following: burns, paralysis and amnesia, eye damage chronic ear infection to hearing loss or muscle or ligament tears. Cardio pulmonary arrests is the primary

cause of death following lightning strike.

Motive Question

• What force is responsible for keeping objects intact? What force is so strong that it can even be a billion, billion, billion, billion times strong than gravity? What force exist between all charged particles?

• One of the strongest fundamental forces in

nature is the electromagnetic force.

Electrostatic force is the manifestation of this force

which involves the interaction of electric

charges that are stationary.

Unlocking of DifficultiesA

Electrostatics

Electric charge

Distance

Repulsion

attraction

B

A.Measure of separation in space

B. Force tending to draw particles together

C. Force tending to draw particles away

D. The study of electric charges at rest

E. Basic element of electricity which is a

fundamental property of matter

F. Unit of charge

COULOMB’S LAW

It was studied and first published in 1783 by French physicist Charles Augustine de Coulomb and was essential to the development of the theory of electromagnetism.

COULOMB’S LAW• The force of attraction or repulsion

between two charges is directly proportional to the magnitude of the charges and inversely proportional to the square of the distance between them.

Diagram describing the basic mechanism of Coulomb's law; like

charges repel each other and opposite

charges attract each other.

His conclusions can be summarized as Coulomb’s law of electrostatics:

“the force of attraction between two charged objects is directly proportional to the product of their charge magnitudes and inversely proportional to the square of the distance between them”

F q1q2

d2

If a proportionality constant is introduced,

Coulomb’s law becomes:

F = kq1q2

d2K = 9.0 x 109 (Nm2/C2)

Charge and Mass of the Electron, Proton and Neutron.

Particle Charge ( C) Mass (kg)

Electron -1.60 ´10+19 9.11 ´10+31

Proton +1.60 ´10+19 1.67 ´10+27

Neutron 0 1.67 ´10+27

Example•Example A

Suppose that two point charges, each with a charge of +1.00 Coulomb are separated by a distance of 1.00 meter. Determine the magnitude of the electrical force of repulsion between them.

Given:• Q1 = 1.00 CQ2 = 1.00 C• d = 1.00 m

Find:Felect = ?

F = (9.0 x 109 N•m2/C2)(1.00 C) • (1.00 C)

(1.00 m)2

Answer

Felect = 9.0 x 109 N

Example

•Example BTwo balloons with charges

of +3.37 µC and -8.21 µC attract each other with a force of 0.0626 Newton. Determine the separation distance between the two balloons.

Given:Q1 = +3.37 µC = +3.37 x 10-6CQ2 = -8.21 µC = -8.21 x 10-6 CF  = -0.0626 N (use a (-) force value since it is repulsive)

Find:d = ?

Answer

d = 1.99 m

Exercises1. Determine the electrical force of attraction between two balloons with separate charges of +3.5 x 10-8 C and -2.9 x 10-8 C when separated by a distance of 0.65 m.

ANSWER

-1.85 x 10-5 N

2.Determine the electrical force of attraction between two balloons that are charged with the opposite type of charge but the same quantity of charge. The charge on the balloons is 6.0 x 10-7 C and they are separated by a distance of 0.50 m.

ANSWER

1.30 x 10-2N

3. What is the charge of the body that will repel another body of charge 6.4 x 10-6 C with a force of 2.7 x10-1 N when they are 0.84 m. apart?

Answer

3.31 x 10-6 C

Evaluation… identify the ff:

1. He is a French physicist who discovered the inverse square relationship between distance and the product of the two charged body.

2. The kind of force that exists between two negatively charged body.

3. The relationship between the force and the distance between two charged object.

4. Unit of charged body.

5. Formula of coulomb’s law.

Agreement• Read, understand and analyze the problem

below. Then solve and show your complete solution.

–A Hydrogen atom is composed of an electron and proton. The Bohr radius, the radius of a hydrogen atom is 5.30 x 10-11m. What is the force of attraction between the proton and the electron in the atom?