AP Physics C: E&M free practice questions with answers
Read question 1 and its full worked answer from paper 1 of our 20-paper AP Physics C: E&M set, then download the 4-page PDF. These are original practice questions, not official past papers. Page updated 3 November 2026.
The electric flux through a closed surface is zero. Which of the following must be true?
A There are no charges inside or outside the surface
B The net charge enclosed by the surface is zero
C The electric field is zero everywhere on the surface
D The surface is inside a conductor
[Gauss's law]
Correct answer: B — The net charge enclosed by the surface is zero
- Gauss's law: Φ = Qenc/ε₀.
- Zero flux means Qenc = 0; the field itself need not be zero.
- Why the other options are wrong:
- A (There are no charges inside or outside the surface): charges outside the surface may exist
- C (The electric field is zero everywhere on the surface): the field may be non-zero with equal inward and outward flux
- D (The surface is inside a conductor): this is only one possibility
Gauss's law relates the TOTAL flux to the ENCLOSED charge only — a zero flux does not mean zero field.
Your sample is downloading. Liked it? AP Physics C: E&M Paper 1 is the full paper: 35 multiple-choice questions and 3 free-response questions (15 marks each), 90 minutes, 80 marks in all, with a worked solution for every question.
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Questions about this sample
What is in the AP Physics C: E&M free sample?
The first 3 questions from paper 1 of the set, in the real exam layout, followed by the step-by-step worked answers. It is a 4-page PDF; this page shows question 1 with its answer.
How many full AP Physics C: E&M papers are there?
20 original papers for students preparing for the AP Physics C: E&M exam. Each is 35 multiple-choice questions and 3 free-response questions (15 marks each), 90 minutes, 80 marks in all, with a worked solution for every question. Papers start at A$11.99 and download instantly as a PDF.
Are these official past papers?
No. The sample is taken from our own original practice paper and is not an official past paper or affiliated with any exam authority.