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AP Course

AP Physics C: Electricity and Magnetism

Updated for the AP Physics C: Electricity and Magnetism framework effective fall 2024, with calculus-based fields, circuits, and induction.

Build calculus-based E&M with original field models, derivations, experiments, quizzes, and practice sets.

Lessons
Electric Charge and Electric ForceConservation of Electric Charge and the Process of ChargingElectric FieldsElectric Fields of Charge DistributionsElectric FluxGauss’s LawElectric Potential EnergyElectric PotentialConservation of Electric EnergyElectrostatics with ConductorsRedistribution of Charge between ConductorsCapacitorsDielectricsElectric CurrentSimple CircuitsResistance, Resistivity, and Ohm’s LawElectric PowerCompound Direct Current CircuitsKirchhoff’s Loop RuleKirchhoff’s Junction RuleResistor Capacitor (RC) CircuitsMagnetic FieldsMagnetism and Moving ChargesMagnetic Fields of Current-Carrying Wires and the Biot-Savart LawAmpère’s LawMagnetic FluxElectromagnetic InductionInduced Currents and Magnetic ForcesInductanceCircuits with Resistors and Inductors (LR Circuits)Circuits with Capacitors and Inductors (LC Circuits)
Quizzes
Practice Problems Formula notes, diagrams, and practice sets will be added here.

AP Physics C: Electricity and Magnetism · Unit 13 · Topic 13.1

Magnetic Flux

Changing magnetic flux creates electric circulation, induced current, inductive energy, and coupled electric-magnetic dynamics.

1. Topic Lens

Magnetic Flux is studied through electromagnetic induction. Connect the system boundary, interacting parts, and measurable evidence before applying a formula.

\[\mathcal E=-\frac{d\Phi_B}{dt}\]

2. Why the Formula Works

The relationship is built from definitions and conservation reasoning:

  1. A moving rod sweeps area at rate dA/dt=Lv.
  2. For uniform perpendicular B, flux is ΦB=BA.
  3. Faraday's law gives magnitude |ℰ|=B(dA/dt)=BLv; Lenz's law supplies the direction.
\[\mathcal E=BLv\quad\text{for perpendicular uniform motion}\]

3. Detailed Visual Model

Pixel diagram for Magnetic FluxOriginal schematic connecting Magnetic Flux to Electromagnetic Induction.+
Magnetic Flux: an original pixel-style model. Use it as a schematic, not a literal scale drawing.

4. Worked Example and Lab Link

A 0.50 m rod moves at 4 m/s perpendicular to a 2 T field. Find motional emf.

Answer: |ℰ|=(2)(0.50)(4)=4 V.

Investigation idea: Move a magnet through a coil at varied speeds and compare signed voltage-area with flux change.

Common trap: The minus sign represents opposition to flux change, not a claim that induced emf is numerically negative in every coordinate choice.

Checkpoint · Topic 13.1

Explain how magnetic flux supports or limits this conclusion: |ℰ|=(2)(0.50)(4)=4 V.

Official curriculum reference: College Board AP Physics C: Electricity and Magnetism course page. The explanation and worked example are independently written for this study site.