AP Physics C: Electricity and Magnetism Exam Guide and Review
AP Physics C: Electricity and Magnetism Exam Guide and Review
This 53-page review connects charge distributions, fields, flux, potential, conductors, capacitance, circuits, magnetic forces, and induction through one response routine: choose the geometry and signs, write the governing relation, carry calculus and SI units, and interpret the answer with symmetry, endpoints, and limiting behavior.
- 53-page review
- 6 course units
- 3-hour exam
- 42 MCQ · 4 FRQ
- Calculator in both sections
- Choose geometry before algebra. Name the source, surface, path, axis, and positive direction before writing an integral or loop equation.
- Use calculus as a physical statement. Explain what each derivative, integral, bound, and constant represents in the electrical or magnetic model.
- Audit every result. Check SI units, vector direction, boundary behavior, continuity, and the immediate and long-time limits.
Study the units in their current order
The ranges below describe each unit's share of the multiple-choice section. They are not shares of the whole exam and do not predict a fixed number of questions. Use them to balance practice while revisiting every unit.
Three hours, two equally weighted sections
The current format gives equal score weight to multiple choice and free response. A four-function, scientific, or graphing calculator may be used in both sections. Treat the 85-minute and 95-minute limits as separate pacing jobs.
| Section | Current format | Calculator |
|---|---|---|
| Multiple choice | 42 questions · 85 minutes · 50% of the exam score | Allowed |
| Free response | 4 questions · 95 minutes · 50% of the exam score | Allowed |
| Complete exam | 3 hours | Allowed throughout |
Check the official AP Physics C: Electricity and Magnetism exam page and the current course and exam description for later changes. These numbers are stated as of 2026-08-29.
Derive the RC equation before evaluating the state
All component values below were created for this guide.
- Step 1Choose current toward the initially uncharged plate. Write the active-loop equation 9.00 V − I(2.00 × 10^6 Ω) − q/(3.00 × 10^-6 F) = 0 and use I = dq/dt.
- Step 2Calculate RC = 6.00 s, then use q(t) = (27.0 μC)[1 − exp(−t/6.00 s)] and I(t) = (4.50 μA)exp(−t/6.00 s).
- Step 3At 12.0 s, exp(−2.00) = 0.135335, so q = 23.3 μC and I = 0.609 μA to three significant figures.
- Step 4Check the endpoints: charge is below its 27.0 μC limit and current is still above zero. The exponent is dimensionless because RC has units of seconds.
| Rubric point | Model element | Common error | Credit |
|---|---|---|---|
| Active-loop equation | Battery rise, resistor drop, capacitor drop, and I = dq/dt use one sign convention. | Writes a memorized exponential without deriving the loop equation. | Full credit when all terms have voltage units and the derivative is present. |
| State evaluation | RC = 6.00 s is placed in a dimensionless exponent before substitution. | Uses q/C as the resistor voltage or drops the exponential sign. | Full credit for a traceable substitution using the stated initial condition. |
| Answer audit | Both electrical quantities carry SI-compatible units and approach correct limits. | Reports a calculator value with no unit or no long-time check. | Full credit when the rounded results and endpoint comparison are explicit. |
Full calculation from the review. Calculation — Choose current toward the initially uncharged plate. The loop rule is 9.00 V − I(2.00 × 10^6 ohm) − q/(3.00 × 10^-6 F) = 0. With I = dq/dt, every term has volts. The time constant is RC = (2.00 × 10^6 ohm)(3.00 × 10^-6 F) = 6.00 s. Thus q(t) = (3.00 × 10^-6 F)(9.00 V)[1 − exp(−t/6.00 s)] and I(t) = (9.00 V)/(2.00 × 10^6 ohm) exp(−t/6.00 s). At 12.0 s, exp(−2.00) = 0.135335, so q = 27.0 microcoulombs × 0.864665 = 23.3 microcoulombs and I = 4.50 microamperes × 0.135335 = 0.609 microamperes.
Set the sign convention before integrating a field A distributed charge creates a field along a chosen axis. Build the integral for the field and determine its direction from the geometry.
Step 1: Choose the coordinate direction and identify the source element. Step 2: Write the differential field contribution with its vector direction. Step 3: Use symmetry to cancel or combine components before integrating. Step 4: Check units, sign, direction, and limiting behavior of the result.
A strong solution makes the geometry, differential contribution, integration limits, and final vector direction consistent.
Fourteen terms to use precisely
These definitions draw from the review appendix. Attach each term to a source, surface, path, circuit, graph, interval, or boundary condition so that it performs a physical job instead of acting as a label.
- electric charge
- A property of matter that determines electric forces and fields.
- electric field
- A vector field describing the electric force that a test charge would experience.
- electric flux
- A measure of the electric field passing through an oriented surface.
- Gauss's law
- A relationship between net electric flux through a closed surface and enclosed charge.
- electric potential
- A scalar field describing electric potential energy per unit charge.
- conductor
- A material in which charge can move in response to an electric field.
- capacitance
- A measure relating stored charge to potential difference.
- current
- The rate at which charge crosses a chosen surface.
- resistance
- A measure relating potential difference to current for a circuit element.
- Kirchhoff's rules
- Rules applying charge and energy conservation to junctions and loops.
- magnetic field
- A vector field that acts on moving charge and magnetic dipoles.
- Lorentz force
- The combined electric and magnetic force on a charged particle.
- Faraday's law
- A relationship between changing magnetic flux and induced electromotive force.
- inductance
- A measure of how changing current produces magnetic flux and induced electromotive force.
What to expect and how to use this review
How is the AP Physics C: Electricity and Magnetism exam organized?
The exam lasts 3 hours. The 42-question multiple-choice section lasts 85 minutes and contributes 50%; the four-question free-response section lasts 95 minutes and contributes 50%.
Can I use a calculator on the exam?
Yes. A calculator is allowed on both the 42-question multiple-choice section and the 4-question free-response section.
How many units are assessed?
The course has six units, from Electric Charges, Fields, and Gauss's Law through Electromagnetic Induction.
How should I use the unit weighting ranges?
The ranges describe each unit's share of the multiple-choice section. Use them to balance review, not to predict an exact exam form.
What calculus connections should I practice?
Practice interpreting derivatives as local rates or gradients and integrals as accumulated contributions. Always connect the calculus operation to the field, potential, charge, current, or flux it represents.
How should I check signs and directions?
Declare a coordinate direction, identify the source and test quantity, and separate vector direction from scalar sign. Then verify the result against symmetry and limiting behavior.
What must I know even though the exam provides an equation sheet?
The exam provides an equation sheet, but it does not tell you which Gaussian surface to choose or why that surface fits the symmetry. You must also choose signs, bounds, paths, and boundary conditions.
Are official multiple-choice questions included in the publicly available materials?
No. The publicly available materials do not include officially released multiple-choice questions for this exam. The multiple-choice practice in this review was independently written for instruction and is not copied from an operational exam.
Use four passes to turn a chapter into exam-ready reasoning
Pass 1 — choose the model without notes. Draw the source distribution, surface, path, circuit, field direction, or changing area. State what symmetry or topology allows before selecting an equation.
Pass 2 — connect representations. Move among field arrows, equipotentials, graphs, circuit diagrams, flux sketches, and algebra. Explain what a slope, signed area, derivative, integral, or time constant means in SI units.
Pass 3 — rebuild the calculus route. Close the equation sheet and write the starting law, source element, bounds, sign convention, and boundary condition from memory. Reopen the sheet only after the physical setup is complete.
Pass 4 — practice under both clocks. Alternate short mixed multiple-choice sets with complete free-response solutions. Use the published unit ranges to size practice, but mix units because one question can connect fields, potential, circuits, magnetism, and induction.
AskSia is not affiliated with or endorsed by College Board®. AP is a registered trademark of College Board®. Exam facts and unit percentages are based on official College Board information as of 2026-08-29. The explanations, numerical settings, and practice questions in this review were independently written for instruction.
