# Electric Force, Field, and Potential

> AP Physics 2 · Unit 3: Electric Force, Field, and Potential
> Source: https://www.owlsprep.com/study/ap-physics-2-u3-overview/
> Weight: 17-23% of total AP Physics 2 exam score

This unit explores core electrostatic concepts that underpin all electricity and magnetism in AP Physics 2, covering charge interactions, fields, potential, energy storage, and simple electric systems.

**Prerequisites:** [AP Physics 1: Work, Energy, and Newtonian Forces](https://www.owlsprep.com/study/ap-physics-1-u4-work-energy-overview/)

## Learning objectives

- Distinguish between electric force, electric field, and electric potential and apply their core relationships to solve problems
- Calculate properties of charge distributions, capacitors, and simple electrostatic electric systems
- Analyze electric interactions qualitatively and quantitatively using both vector and scalar models
- Predict the behavior of charged particles in uniform and non-uniform electric fields

## 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](https://www.owlsprep.com/study/ap-physics-2-u3-capacitance/) — Learn how capacitors store charge and energy, and calculate capacitance for common configurations including parallel plates.
- [AP Physics 2 Charge and Electric Force](https://www.owlsprep.com/study/ap-physics-2-u3-charge-and-electric-force/) — Explore the fundamental property of electric charge and apply Coulomb's law to calculate force between point charges.
- [AP Physics 2 Electric Field](https://www.owlsprep.com/study/ap-physics-2-u3-electric-field/) — Understand the field model of electric interactions, calculate fields from point charges and simple continuous distributions.
- [AP Physics 2 Electric Systems](https://www.owlsprep.com/study/ap-physics-2-u3-electric-systems/) — Apply electrostatics concepts to analyze combinations of charged components and simple electrostatic systems.
- [AP Physics 2 Potential and Electric Potential Energy](https://www.owlsprep.com/study/ap-physics-2-u3-potential-and-electric-potential-energy/) — Connect electric energy to electric potential, and relate potential to electric field for different charge configurations.

## Common pitfalls

- **Wrong:** Confusing electric force, electric field, and electric potential as interchangeable quantities
  - Why it fails: All three are related but have different definitions, units, and vector/scalar properties that lead to incorrect calculations if mixed up
  - Correct: Memorize core definitions: force on a charge, field is force per unit charge, potential is potential energy per unit charge
- **Wrong:** Forgetting the effect of dielectric material on capacitance
  - Why it fails: Many students incorrectly assume dielectrics reduce capacitance, when they actually increase it by reducing internal electric field
  - Correct: Remember $C = \kappa C_0$, where dielectric constant $\kappa > 1$, so capacitance always increases with a dielectric

## 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 | $C = \frac{\kappa \epsilon_0 A}{d}$ |
| Energy stored in a charged capacitor | $U = \frac{1}{2}CV^2 = \frac{Q^2}{2C}$ |

## 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.

- [AP Physics 2 Capacitance](https://www.owlsprep.com/study/ap-physics-2-u3-capacitance/)
- [Electric Systems](https://www.owlsprep.com/study/ap-physics-2-u3-electric-systems/)
- [Charge and Electric Force](https://www.owlsprep.com/study/ap-physics-2-u3-charge-and-electric-force/)

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From [OwlsPrep](https://www.owlsprep.com) — free study guides for A-Level, IB, AP and IGCSE, written against the official syllabus. Canonical page: https://www.owlsprep.com/study/ap-physics-2-u3-overview/