Electric force between point charges

Need to know

What you need to know

• The electrostatic force is directly proportional to the product of the magnitudes of the charges ($F \propto Q_1 Q_2$).
• The force is inversely proportional to the square of the distance separating the charges ($F \propto 1/r^2$).
• Charges of the same sign (both positive or both negative) result in a repulsive force.
• Charges of opposite signs (one positive and one negative) result in an attractive force.
• For practical calculations, the permittivity of air is typically assumed to be the same as a vacuum.

Explanation

Electric force between point charges

1. The electrostatic force is directly proportional to the product of the magnitudes of the charges ($F \propto Q_1 Q_2$).
2. The force is inversely proportional to the square of the distance separating the charges ($F \propto 1/r^2$).
3. Charges of the same sign (both positive or both negative) result in a repulsive force.
4. Charges of opposite signs (one positive and one negative) result in an attractive force.