AP Physics C: Electricity and Magnetism is one of the most challenging AP Physics courses, requiring a strong grasp of calculus-based physics. Whether you’re preparing for the AP exam or reinforcing key concepts, understanding the essential formulas and their applications is crucial for success.
In this guide, we’ll break down all the important formulas you need to know, their meanings, and how to apply them to different physics problems. We’ll also include tables, bullet points, and real-world applications to make everything easier to understand.
Table of Contents
- Electrostatics Formulas
- Gauss’s Law and Electric Fields
- Electric Potential and Capacitance
- Current, Resistance, and Circuits
- Magnetism and Magnetic Fields
- Induction and Electromagnetic Waves
- Final Tips for AP Physics C Exam
AP Physics C Electricity and Magnetism: Electrostatics Formulas
Electrostatics deals with electric charges at rest and their interactions. Here are the key formulas you need to remember:

Application of Coulomb’s Law
Coulomb’s law helps determine the force between two charged particles, such as in atomic physics and electrostatic equilibrium problems.
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AP Physics C Electricity and Magnetism: Gauss’s Law and Electric Fields
Gauss’s Law is a powerful tool for calculating electric fields when there is symmetry.
Gauss’s Law Formula
Where:
d A dA = Differential area element
Q enc Q_{\text{enc}} = Charge enclosed
ε 0 \varepsilon_0 = Permittivity of free space
Common Applications
- Spherical Symmetry: Electric field outside a charged sphere
- Cylindrical Symmetry: Electric field due to an infinite charged wire
- Planar Symmetry: Field near an infinite charged plane
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Electric Potential and Capacitance
Electric potential is the work done per unit charge in moving a charge in an electric field.

Capacitor Applications
Capacitors are widely used in:
- Circuit design
- Energy storage (batteries, power backups)
- Filtering signals in electronics
This section covers Ohm’s Law, circuit equations, and power relationships.
Ohm’s Law
V = I R
V = IR
Where:
V V = Voltage
I I = Current
R R = Resistance
Application in Circuits
- Series Circuits: Total resistance is the sum of individual resistances.
- Parallel Circuits: Inverse of total resistance is the sum of individual reciprocals.
Magnetism and Magnetic Fields
Magnetism arises from moving charges and currents. The key equations include:

Applications of Magnetism
- Electric motors
- Magnetic resonance imaging (MRI)
- Electromagnetic levitation
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Induction and Electromagnetic Waves
Faraday’s Law and Lenz’s Law describe how changing magnetic fields induce voltage.

Faraday’s Law
Where:
E \mathcal{E} = Induced EMF
N N = Number of turns
Φ \Phi = Magnetic flux

Applications of Electromagnetic Induction
- Transformers: Step-up and step-down voltage
- Generators: Convert mechanical energy into electricity
- Wireless charging: Uses induction principles
Final Tips for AP Physics C Exam
- Understand concepts before memorizing formulas – Many formulas are derived from fundamental laws.
- Practice problems regularly – Apply formulas to real-world problems.
- Use diagrams and tables – Visualizing problems makes them easier to solve.
- Take advantage of online resources – Visit College Board AP Physics C for official information.
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