Unit Overview

Electric Force, Field, and Potential

AP Physics 2· 5 min read 📊 17-23% of total AP Physics 2 exam score

1. Unit at a Glance

This unit builds from fundamental properties of charge up to complete electrostatic systems. We develop both force-based and energy-based models for electric interactions, then apply these concepts to capacitors and real-world electric systems. Mastery of these core concepts is critical for all subsequent electricity and magnetism units in AP Physics 2.

Below are the full sub-topics covered in this unit:

AP Physics 2 Capacitance

Learn how capacitors store charge and energy, and calculate capacitance for common configurations including parallel plates.

★★★⏱ 8 min

AP Physics 2 Charge and Electric Force

Explore the fundamental property of electric charge and apply Coulomb's law to calculate force between point charges.

★★⏱ 7 min

AP Physics 2 Electric Field

Understand the field model of electric interactions, calculate fields from point charges and simple continuous distributions.

★★★⏱ 9 min

AP Physics 2 Electric Systems

Apply electrostatics concepts to analyze combinations of charged components and simple electrostatic systems.

★★★★⏱ 8 min

AP Physics 2 Potential and Electric Potential Energy

Connect electric energy to electric potential, and relate potential to electric field for different charge configurations.

★★★⏱ 10 min

2. Common Pitfalls

Wrong move:

Confusing electric force, electric field, and electric potential as interchangeable quantities

Why:

All three are related but have different definitions, units, and vector/scalar properties that lead to incorrect calculations if mixed up

Correct move:

Memorize core definitions: force on a charge, field is force per unit charge, potential is potential energy per unit charge

Wrong move:

Forgetting the effect of dielectric material on capacitance

Why:

Many students incorrectly assume dielectrics reduce capacitance, when they actually increase it by reducing internal electric field

Correct move:

Remember $C = κ C_{0}$ , where dielectric constant $κ > 1$ , so capacitance always increases with a dielectric

3. Quick Reference Cheatsheet

Key Concept	Formula
Coulomb's Law (Force between point charges)	$F = k \frac{∣ q _{1} q _{2} ∣}{r ^{2}}$
Electric Field from a point charge	$E = k \frac{Q}{r ^{2}}$
Electric Potential Energy of two point charges	$U = k \frac{q _{1} q _{2}}{r}$
Electric Potential from a point charge	$V = k \frac{Q}{r}$
Capacitance of a parallel plate capacitor	$C = \frac{κ ϵ _{0} A}{d}$
Energy stored in a charged capacitor	$U = \frac{1}{2} C V^{2} = \frac{Q ^{2}}{2 C}$

What's Next

Begin your study of this unit by accessing the first sub-topic below. Once you complete all sub-topics in this unit, you can move on to the first sub-topic of the next unit (Electric Circuits) to continue building your AP Physics 2 knowledge.