ELECTRIC FIELDLESSON 2

WARM UP

What happens when

a) like charges come together?

b) Unlike charges come together?

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.

Coulomb’s Law – Gives the electric force between two point charges.

2

21

r

qqkF

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

Coulombs law

ϵ0= permittivity of free space=8.85 X 10-12 F/m

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

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.

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?

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.