1. COULOMB’S LAW
Coulomb’s Law – charges exert forces on each other and have been shown to be
directly proportional to the magnitude
of the charge and
inversely proportional to the distance
between the charges.

2. r2 F = k q1 q2 k = electrostatic constant = 8.99 x109 N m2/C2
k = electrostatic constant = x109 N m2/C2
q1 = charge measured in coulombs (C)
q2 = charge measured in coulombs (C)
r = distance between charged particles in meters (m)

3. Electric Force
like all other force is a vector quantity.

4. In the diagram,
the direction of force on the positively charged object A when object B is brought near is repulsive. And the sign of the force is positive.
If object B were negatively charged, the force on object A is attractive. The force is in the opposite direction and the sign of the force is negative.

5. The electrons are
more loosely bound outside the nucleus.
Therefore electrons (e-) rather than protons are transferred in a charging process.

6. -0.0005 C at a separation of 20.0 meters? example:
example: What is the force between two electrostatic point charges of C and
C at a separation of 20.0 meters?
example:
Object A has a charge of +6.0x10-6 C
Object B has a charge of -3.00x10-6 C and is m to the right of Object A.
Object C has a charge of +1.5x10-6 C and is 0.03 m below Object A.
What is the net force on A?