AP Physics C: Electricity and Magnetism

Advanced Placement Physics C: Electricity and Magnetism with calculus applications.

Basic Concepts

Electrostatics and Coulomb’s Law

Understanding Electric Charge

Electric charge is a fundamental property of matter carried by particles like protons and electrons. Like charges repel, and opposite charges attract, creating the basis for all electric phenomena.

Coulomb’s Law

The force between two point charges can be determined by Coulomb’s Law. This law describes how the force changes with distance and charge magnitude:

\[ F = k_e \frac{|q_1 q_2|}{r^2} \] where \( F \) is the electrostatic force, \( k_e \) is Coulomb’s constant (\( 8.99 \times 10^9 \) N·m²/C²), \( q_1 \) and \( q_2 \) are the charges, and \( r \) is the separation between them.

Visualizing Electric Fields

Charges create electric fields around them. Field lines point away from positive and toward negative charges, showing the direction a positive test charge would move.

Superposition Principle

When more than two charges are present, the net force on any charge is the vector sum of the individual forces from all other charges.

Real-World Connection

Static electricity that makes your hair stand on end is a result of electrostatic forces between charged hairs!

Key Formula

\[F = k_e \frac{|q_1 q_2|}{r^2}\]

Examples

  • Calculating the force between two electrons separated by 1 nm.

  • Finding the net force on a charge placed between two other charges.

In a Nutshell

Coulomb’s Law quantifies the electric force between two point charges and helps explain how electric fields work.

Key Terms

Electric Field
A region around a charged object where electric forces are exerted on other charges.
Superposition Principle
The net force on a charge is the sum of forces from all other charges.