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Unit 2 · Electric Force, Field, & Potential Flashcards Cheat Sheet Essentials Visual Review MC Practice FRQ Practice

AP Physics 2 Unit 2 Visual Review

A topic-by-topic visual walkthrough of Unit 2: Electric Force, Field & Potential — Coulomb's law, charging, electric fields, potential energy and potential, and capacitors.

← Back to Unit 2 hub
TOPIC 2.1 Electric Charge & Electric Force Coulomb's Law F = k q₁q₂ / r² k = 8.99×10⁹ N·m²/C² Force between two point charges — along the line joining them. Inverse-square: double r → force drops to ¼. + − opposite charges ATTRACT like charges repel · charge unit = coulomb (C) Charge is quantized All charge is a multiple of e = 1.6×10⁻¹⁹ C. Protons are +e, electrons −e; net charge q = ±Ne. F = kq₁q₂/r²; like repels, opposite attracts; charge is quantized in units of e. The Review Hub · AP Physics 2 · Unit 2 TOPIC 2.2 Conservation of Charge & Charging Charge is conserved — never created or destroyed, only transferred Friction Rubbing transfers electrons between two materials. balloon on hair Both end up charged, opposite & equal. Conduction Direct contact with a charged object shares charge. touching a charged rod Object gains the SAME sign of charge. Induction A nearby charge polarizes a conductor; grounding then leaves net charge. no contact needed Object gains the OPPOSITE sign. Total charge is conserved; charge by friction, conduction (same sign), or induction (opposite). The Review Hub · AP Physics 2 · Unit 2 TOPIC 2.3 Electric Fields Field = force per unit charge E = F / q = k Q / r² E is a VECTOR (N/C), pointing the way a + test charge would be pushed. Field lines point AWAY from + charges, TOWARD − charges. + field lines radiate outward from + charge Uniform field between parallel plates Between charged plates the field is uniform: E = V/d. A charge feels F = qE everywhere between them. E = F/q = kQ/r² (vector, N/C); lines leave + and enter −; F = qE. The Review Hub · AP Physics 2 · Unit 2 TOPIC 2.4 Electric Potential Energy Two point charges U = k q₁q₂ / r Note: 1/r, not 1/r² (that's force). Like charges: U > 0 (stored, want to fly apart). Opposite: U < 0 (bound). Work-energy: W = −ΔU as charges move. Uniform field Moving charge q a distance d along E: ΔU = q·E·d (analogous to mgh) A + charge speeds up moving from high to low potential — U → KE. Energy is conserved: KE + U = constant. Gravity analogy Electric PE works just like gravitational PE — a charge "falls" through a field, converting U into kinetic energy. U = kq₁q₂/r (1/r!); in a uniform field ΔU = qEd; energy is conserved. The Review Hub · AP Physics 2 · Unit 2 TOPIC 2.5 Electric Potential Potential = energy per charge V = U / q = k Q / r V is a SCALAR, measured in volts (1 V = 1 J/C). No direction! From several charges, add potentials as simple numbers (with sign). Potential difference & field Uniform field relation: E = ΔV / d Field points from HIGH to LOW potential. Work to move q: W = qΔV. Equipotential lines ⊥ field lines. Potential (scalar) vs. field (vector) V tells you energy per charge (a number); E tells you force per charge (a direction). Don't confuse them. V = kQ/r (scalar, volts); E = ΔV/d; field points high → low potential. The Review Hub · AP Physics 2 · Unit 2 TOPIC 2.6 Capacitors Storing charge & energy Q = C V C = capacitance (farads). Bigger C holds more charge at the same voltage. U = ½ C V² = ½ Q V energy stored in the electric field. +Q −Q parallel plates store equal & opposite charge C = ε₀ A / d Geometry sets C For parallel plates C = ε₀A/d: bigger plate area A or smaller gap d → larger capacitance. A dielectric raises C. Q = CV, U = ½CV²; C = ε₀A/d depends on plate geometry. The Review Hub · AP Physics 2 · Unit 2 TOPIC 2.7 Conservation of Electric Energy KE + U = constant (isolated system) Worked example A proton accelerates through ΔV = 500 V: KE = qΔV = (1.6e−19)(500) = 8.0×10⁻¹⁷ J Then solve ½mv² = KE for the speed v. 1 electron-volt (eV) = 1.6×10⁻¹⁹ J. The big idea As a charge moves through a field, energy shuttles between electric PE and KE, but the TOTAL stays constant. + charges accelerate high→low V; − charges accelerate low→high V. Same energy-conservation logic as mechanics. Energy is conserved: KE + U = constant; a charge gains KE = qΔV. The Review Hub · AP Physics 2 · Unit 2
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How to use the visual review

Spend 30 seconds per slide before clicking next. Look at the diagram, then ask yourself: "Could I draw this from memory and explain it?"

Use the fullscreen button () on desktop for the best experience. Use arrow keys to navigate. Tap "Show all slides" to jump around.

This is great for review the night before the exam — fast, visual, and covers everything you need to remember about Unit 2's electric force, field, and potential.