Lecture 02

Question 1

What does coulomb’s law state?

Answer 1

The magnitude of electrostatic force of repulsion or attraction between any two point charges is directly proportional to the product of magnitude of charges and inversely proportional to the square of the distance between them. The force is along the straight line joining them.

Question 2

What is the similarity between coulomb’s law and gravitational law?

Answer 2

Inverse square law
Acts along the line joining the centres

Question 3

Difference between coulomb’s law and gravitational law?

Answer 3

Coulombs
Force is repulsive as well as attractive
Depends on medium

Gravitational
Only attractive
Independent of medium.

Question 4

What is the value of dielectric constant ?

Answer 4

k = 9 x 10^9

Question 5

What is the value of gravitational constant?

Answer 5

G = 6.67 x 10^-11

Question 6

Limitations of Coulombs Law?

Answer 6

1. Valid only for point charges
2. Both charges have to be at rest (can’t be in motion)

Question 7

Principle of superposition

Answer 7

In a system of n charges the net electrostatic force on any charge is the vector sum of the forces due to remaining charges on this charge.

Question 8

When solving a question based on third charge in equilibrium type?

Answer 8

When charges opposite: near the smaller charge (outside)