Topic 1: Charges & Forces

Question 1

How was coulombs law derived? What does it show?

Answer 1

Coulomb’s law, derived experimentally in 1785, gives the electrostatic force between two charges.

Question 2

Diagram and equation for Coulomb’s law?

Answer 2

Question 3

Description of Coulomb’s law equation?

Answer 3

Question 4

The permittivity of free space?

Answer 4

Question 5

The elementary charge?

Answer 5

1.60217733´10^-19 C

Question 6

The Scalers and vectors present in Coulomb’s law?

Answer 6

F₁₂ & r₂₁ are vectors.

They have magnitude and direction.

r₂₁ is a unit vector, unit magnitude

(The Hat means magnitude)

Note: F₁₂ = -F₂₁

Question 7

In coulombs law the Force and charge are related……

Answer 7

Related by the inverse square.

Question 8

What happens when many forces are present

Answer 8

With many charges present (distribution) then the resultant forces must be added vectorially. The resultant force, F0 is:

Question 9

The equation for Superposition of charges via coulombs law?

Answer 9

Question 10

Finding the force exerted on a charge Q₀ on the axis of a charged ring of radius R.

The equation for an elemental charge:

Answer 10

Question 11

Finding the force exerted on a charge Q0 on the axis of a charged ring of radius R.

The force that this elemental charge exerts on Q₀ is

Answer 11