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Volume I · MMXXVI AP Physics 2: Algebra-Based
Library› AP Physics 2: Algebra-Based› Unit 10: Electric Force, Field, and Potential
⁂   AP Physics 2: Algebra-Based · Unit 10

10. Electric Force, Field, and Potential

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

15–18% exam weight

Unit 10: Electric Force, Field, and Potential

Unit 10 (Electric Force, Field, and Potential) 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. Coulomb's law (F = kq₁q₂/r²)
  2. Electric fields from point charges and charge distributions (E = kq/r²)
  3. Superposition principle for electric fields and forces
  4. Electric potential energy (U = qV)
  5. Electric potential (V = kq/r) and the distinction from potential energy
  6. Equipotential surfaces and their relationship to field lines
  7. Capacitors: definition, capacitance (C = Q/V), energy stored
  8. Charge distributions on conductors (surface charge, shielding)
  9. Conductors vs. insulators in electric fields
  10. Gauss's Law (conceptual application)

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

Conflating electric potential (V, a scalar, measured in J/C) with electric potential energy (U = qV, measured in J) — FRQ rubrics distinguish these explicitly and award no credit for using them interchangeably

Common error

Reversing the direction of electric force on negative charges: field lines point from + to −, but the force on a negative charge is opposite to the field direction; students who memorize 'force follows field' lose points on direction-based FRQ parts

Common error

Failing to apply superposition correctly for multiple charges — summing magnitudes of fields instead of summing vector components, or summing potential energy values with incorrect signs

Common error

Treating capacitor energy as U = QV instead of U = ½QV = ½CV² — the factor of ½ arises from the charging process and is frequently dropped under exam pressure

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?
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