AP® Physics C: Electricity and Magnetism

Flashcards

204 cards with the terms and ideas you need to know cold. The ones you find hard come back sooner.

Multiple choice practice

362 exam-style questions, timed like the real exam, with every answer explained.

Practice exam

The whole multiple choice section: 42 questions in 1 hour 25 minutes, weighted by unit like the real exam. A fresh mix every time.

Must-know sheet

The facts, rules and terms to know cold on exam day, on one page. Filter it by unit, or print it.

Free-response practice

24 free-response questions like the ones on the exam. Score your answer with the rubric and a model answer, or sign in for free AI scoring.

Electric Charges, Fields, and Gauss’s Law

6 topics · 36 videos

• Like charges repel, opposite charges attract, and charge is always conserved
• An electric field tells you the force per unit charge at every point
• Fields from several charges add as vectors
• Add up tiny pieces of charge with an integral to find the field of a continuous distribution
• Gauss’s law links the flux through a closed surface to the charge inside it

Electric Potential

3 topics · 20 videos

• Electric potential energy belongs to a system of interacting charges
• Electric potential is potential energy per unit charge, and potentials add as plain numbers
• The field points toward lower potential: $E_x = -\frac{dV}{dx}$
• Equipotential lines always cross field lines at right angles
• A charge moving through a potential difference trades potential energy for kinetic energy

Conductors and Capacitors

4 topics · 27 videos

• A conductor in equilibrium has zero field inside and is one equipotential
• Charge flows between connected conductors until they reach the same potential
• Capacitance depends only on a capacitor’s shape and what’s between its plates
• A charged capacitor stores energy in its electric field
• A dielectric weakens the field between the plates and raises the capacitance

Electric Circuits

8 topics · 50 videos

• Current is the rate charge flows past a point: $I = \frac{dq}{dt}$
• Resistance depends on the material, the length and the cross-sectional area
• Series elements share the same current; parallel branches share the same potential difference
• Kirchhoff’s rules come from conservation of energy and conservation of charge
• In an RC circuit a capacitor charges and discharges exponentially, with time constant $\tau = RC$

Magnetic Fields and Electromagnetism

4 topics · 26 videos

• Magnetic field lines always form closed loops: there are no magnetic monopoles
• A magnetic field pushes on a moving charge with $\vec{F} = q\vec{v} \times \vec{B}$
• Magnetic force is perpendicular to velocity, so it changes a charge’s direction, not its speed
• Currents make magnetic fields that circle around the wire
• Ampère’s law finds the field quickly when the current has symmetry

Electromagnetic Induction

6 topics · 39 videos

• Magnetic flux measures how much field passes through an area
• A changing flux induces an emf: $\mathcal{E} = -\frac{d\Phi_B}{dt}$
• Lenz’s law: the induced current opposes the change in flux
• Inductors resist changes in current and store energy in their magnetic field
• LR circuits change exponentially; LC circuits oscillate like a mass on a spring