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AP Physics C E&M Past Papers and Drilling: Gauss’s Law, Capacitors, Circuits, Induction
TUTORZONE ORIGINAL DRILLING MOCK · AP PHYSICS C: E&M
Written to the current College Board format: Section I multiple choice, 42 questions, 85 min, 50%; Section II free response, 4 questions, 95 min, 50% (mathematical routines, translation between representations, experimental design, qualitative/quantitative). The course runs six units (Units 8-13) with calculators allowed throughout. This drilling mock demonstrates 6 questions with answers and techniques.
What is in the AP Physics C: E&M exam?
Direct answer: the exam runs 3 hours: multiple choice 42 questions, 85 min, 50%; free response 4 questions, 95 min, 50%, across six units.
Assessment at a glance (2027)
| Component | Content | Weighting | Duration |
|---|---|---|---|
| Section II (Free Response) | 4: routines, representations, experiment, qualitative | 50% | 95 min |
| Section I (Multiple Choice) | 42: discrete + question sets | 50% | 85 min |
AP Physics C E&M drilling technique: keep the electric field (vector) and potential (scalar) apart; work uses W = q times delta V; the RC time constant is tau = RC; the induced emf is N A dB/dt – never drop the number of turns. Of the six units, Electric Charges, Fields and Gauss’s Law is 15-25% and Electric Circuits 15-25%.
How this paper was built
This is a TutorZone original drilling mock: the questions follow the College Board AP Physics C: E&M format and the answers are our own, not College Board past papers or marking references.
Every numeric answer was recomputed programmatically; the exam structure and unit weightings come from the official course and exam description.
E&M and Mechanics are two separate papers that can be taken on the same day; the six questions here cover the electric field, potential, capacitors, RC circuits, magnetic force and induction.
Pacing
| Section | Marks | Suggested time | What to do first |
|---|---|---|---|
| Section II (Free Response) | 50% | about 24 min per question | write integral, substitute, units |
| Section I (Multiple Choice) | 50% | about 2 min per question | dimensional check and graph reasoning |
Which E&M unit carries the most weight?
Direct answer: in the multiple-choice section, Electric Charges, Fields and Gauss’s Law is 15-25% and Electric Circuits is also 15-25%; potential, capacitors, magnetism and induction take 10-20% each.
Drilling (6 demonstrated)
Demonstrates the field of a point charge, potential and work, capacitor energy, the RC time constant, magnetic force and electromagnetic induction.
Question 1 (8 marks)
A point charge Q = +8 x 10^-9 C sits in vacuum. Find the electric field strength 0.2 m away (k = 9 x 10^9 N m^2/C^2).
Question 2 (8 marks)
A point charge Q = +5 x 10^-9 C. Find the potential 0.5 m away, and the work needed to bring +2 x 10^-9 C from infinity to that point.
Question 3 (8 marks)
A 2 microfarad capacitor is connected to a 12 V supply. Find the stored charge and energy.
Question 4 (8 marks)
A 10 kilo-ohm resistor and a 100 microfarad capacitor form an RC circuit. Find the time constant and state the capacitor voltage after one time constant.
Question 5 (8 marks)
A 0.3 m straight wire carries 4 A in a uniform 0.5 T magnetic field perpendicular to the wire. Find the magnetic force and describe its direction.
Question 6 (8 marks)
A 200-turn coil has area 0.01 m^2 per turn. A perpendicular magnetic flux density rises uniformly from 0 to 0.2 T in 0.5 s. Find the induced emf.
Which topics does this paper drill?
Direct answer: the field of a point charge, potential and work, capacitor energy, the RC time constant, magnetic force, and electromagnetic induction.
Answers and marks per question
Question 1
E = kQ/r^2 = (9 x 10^9 x 8 x 10^-9) / 0.04 = 1800 N/C (8), directed radially outward from the positive charge.
Question 2
V = kQ/r = (9 x 10^9 x 5 x 10^-9) / 0.5 = 90 V (4); W = qV = 2 x 10^-9 x 90 = 1.8 x 10^-7 J (4).
Question 3
Q = CV = 2 x 10^-6 x 12 = 24 microC (4); U = 0.5CV^2 = 0.5 x 2 x 10^-6 x 144 = 1.44 x 10^-4 J (144 microJ) (4).
Question 4
tau = RC = 10 x 10^3 x 100 x 10^-6 = 1.0 s (4); after one time constant the voltage is about 63% of its final value (4).
Question 5
F = BIL = 0.5 x 4 x 0.3 = 0.6 N (6); the force is perpendicular to both the current and the field (right-hand rule, 2).
Question 6
emf = N A dB/dt = 200 x 0.01 x 0.2 / 0.5 = 0.8 V (8). Forgetting the number of turns N is the usual lost mark.
Where are the marks usually lost?
Direct answer: using potential where a field is needed, dropping the number of turns N in induced emf, and unit conversion for kilo-ohm and microfarad – all three are in the pitfalls table.
Where these marks are usually lost
| Mistake | What it looks like | What it costs | Instead |
|---|---|---|---|
| Mixing field and potential | Use V to get a force | Field is a vector, potential a scalar | Keep E = kQ/r^2 and V = kQ/r apart |
| Dropping N in induction | Write A dB/dt only | Loses the whole 8 marks | emf = N A dB/dt |
| Wrong RC units | Treat 10 kilo-ohm as 10 ohm | Time constant out by 1000 | Convert to 10 x 10^3 ohm first |
How to use this paper
First drill: all 6 questions on the clock, equation sheet closed.
Mark it: check unit conversions (microfarad, kilo-ohm, 10^-9) and vector directions.
Second drill: redo three to seven days later, focusing on the induction and RC questions.
What should I do after drilling this paper?
Direct answer: log the unit-conversion and direction errors; redo the induction and RC questions in three to seven days; then drill the AP Physics C Mechanics paper.
FAQ
Is this a College Board past paper?
No. The questions and answers are TutorZone originals, not College Board past papers or marking references.
What is in the AP Physics C: E&M exam?
3 hours: 42 multiple-choice questions in 85 min (50%) and 4 free-response questions in 95 min (50%), over six units (Units 8-13).
Can I take E&M and Mechanics in the same year?
Yes – they are two separate papers, sat on the same day, and scored independently.
Official references
| Resource | What to check |
|---|---|
| College Board AP Physics C: E&M exam page | Confirm the format and question counts |
| Official course and exam description (CED) | Check the six-unit multiple-choice weightings |
| https://www.tutorzone.com.hk/en-ap-physics-c-mechanics-mock-2027/ | AP Physics C Mechanics drilling mock |
| https://www.tutorzone.com.hk/en-ap-physics-2-mock-2027/ | AP Physics 2 drilling mock (algebra-based E&M) |
Related: practice area · AP Physics C Mechanics drilling mock · AP Physics 2 drilling mock
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