Point charge

Definition

A point charge is a hypothetical charge located at a single point in space with no physical size or structure. It is used to simplify the analysis of electric fields and forces in electrostatic problems.

5 Must Know Facts For Your Next Test

1. The electric field produced by a point charge decreases with the square of the distance from the charge, following Coulomb's law: $E = \frac{kQ}{r^2}$.
2. The direction of the electric field created by a positive point charge is radially outward, while it is radially inward for a negative point charge.
3. Point charges are idealizations that help simplify calculations in electrostatics; real charges often have spatial extent but can be approximated as point charges if they are small enough.
4. When multiple point charges are present, the net electric field at any location is found by vector addition of the individual fields produced by each charge.
5. The potential energy of a system of two point charges depends on their magnitudes and separation distance: $U = \frac{kQ_1Q_2}{r}$.

Review Questions

• How does the electric field produced by a point charge vary with distance?
• What is the difference between the electric fields produced by positive and negative point charges?
• How do you determine the net electric field when multiple point charges are present?

Related terms

Electric Field:

A region around a charged particle where an electric force would be exerted on other charged particles.

Coulomb's Law:

$F = k \frac{{|Q_1 Q_2|}}{{r^2}}$, describes the force between two point charges.

Electrostatic Potential Energy: $U = k \frac{{Q_1 Q_2}}{{r}}$, represents the energy due to positions of charged objects.