Tian2
The Tian2 Study Library AP Edition · Tian2 Editorial Bureau
Volume I · MMXXVI AP Physics 2: Algebra-Based
Library› AP Physics 2: Algebra-Based› Unit 11: Electric Circuits
⁂   AP Physics 2: Algebra-Based · Unit 11

11. Electric Circuits

15–18% of the AP exam. 10 key topics. 4 common errors analyzed.

15–18% exam weight

Unit 11: Electric Circuits

Unit 11 (Electric Circuits) extends the AP Physics 2 curriculum. Emphasize conceptual justification: FRQ scoring rubrics award points for physical reasoning stated in precise sentences.

Key topics in this unit

  1. Ohm's law (V = IR) and resistance
  2. Series and parallel resistor circuits
  3. Equivalent resistance (series: R_eq = R₁ + R₂; parallel: 1/R_eq = 1/R₁ + 1/R₂)
  4. Kirchhoff's current rule (junction rule)
  5. Kirchhoff's voltage rule (loop rule)
  6. Power dissipation (P = IV = I²R = V²/R)
  7. Capacitors in circuits: charge, voltage, and energy
  8. RC circuits: charging and discharging behavior (exponential transients, time constant τ = RC)
  9. Voltmeters and ammeters: ideal behavior and placement in circuits
  10. Internal resistance of batteries

Common errors — what the rubric penalizes

These are the most frequently penalized mistakes on AP exam FRQs and MCQs. Review each before your next practice session.

Common error

Inverting the parallel resistance formula — computing R_eq = R₁ + R₂ for parallel branches (the series formula) instead of applying 1/R_eq = 1/R₁ + 1/R₂; also forgetting to take the reciprocal of the sum of reciprocals

Common error

Misidentifying current in branches of a parallel circuit — applying total current to each branch rather than recognizing that branches with lower resistance carry more current; Kirchhoff junction rule errors follow from this conceptual gap

Common error

RC transient analysis errors: students correctly handle steady-state circuits but cannot reason about immediately-after-switching conditions (capacitor acts as short) vs. fully-charged conditions (capacitor acts as open); they also omit the exponential decay shape when sketching I vs. t or V vs. t graphs

Common error

Kirchhoff's voltage loop sign errors — traversing a resistor against current direction (voltage rise) vs. with current direction (voltage drop) requires consistent sign assignment; students often flip signs for EMF sources or resistors mid-loop

Study checklist

  • Can you list all key topics from memory without this page?
  • Have you worked through at least one FRQ-style question per topic?
  • Can you explain each common error above — and why the correct answer differs?
  • Have you reviewed the relevant College Board CED section and formula sheet entries?
← Electric Force, Field, and PotentialMagnetism and Electromagnetism →
← Back to AP Physics 2: Algebra-Based
Our worked solutions and practice questions are original instructional content created by Tian2 AP. They are aligned to the concepts and skills described in College Board’s Course and Exam Description and are not reproductions of, or affiliated with, College Board’s official materials.