1. WARM UP
What happens when
a) like charges come together?
b) Unlike charges come together?

2. LEARNING OBJECTIVES
The students will be able to
1.Recall and use Coulomb’s law in the form F = kQ1
Q2 / r2 for the force between two point charges in
free space or air ( k = 9.0 x 109 N m 2/c2)
2.Apply coulombs law to do problems.
3. recognize the analogy between certain
qualitative and quantitative aspects of Coulomb’s
law of charge and Newton’s law of gravitation.

3. Coulomb’s Law – Gives the electric
force between two point charges.
q q
1 2
r
2
F  k
Inverse Square
Law
k = Coulomb’s Constant = 9.0x109 Nm2/C2
q1 = Point charge -1
q2 = Point charge - 2
r = the distance between the two charges

4. Coulombs law
ϵ0= permittivity of free
space=8.85 X 10-12 F/m

5. Comparison of newton’s law of gravitation and
coulomb’s law

6. Final Assessment
1.State coulomb’s law.
2.If we double the distance between the two
charges, what happens to the force between
them?
3.What do you call the force between two point
masses?
4.Compare Newtons law of gravitation and
coulombs law
5.Problem on page 255.

7. Continous assessment
1.State coulomb’s law ?
2.How is the coulomb’s force
affected if the distance between
charges is a)increased? b) decreased
3. Why do you call coulomb’s law as
inverse square law?

8. HOME WORK
1.What happens to the electrostatic force between
two charges if the distance between them is a)
tripled? B)halved? C)doubled
2.Why is coulombs law known as inverse square
law?
3.Numerical on page 255.(Example1)
4 The magnitudes of two point charges are
doubled.How would you adjust the distance
between them so that the force remains the same.