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Current Courses

AP Physics 2

Algebra-based second-year physics: thermodynamics, electricity and magnetism, optics, and modern physics. Seven units, one lesson each. Units 1, 2 and 3 are written, each with a bench lab and interactive labs you can actually run; the rest are queued.

Units

Unit 1 · 5 labs

Thermodynamics

Ideal gases, kinetic theory, thermal expansion, specific heat, PV diagrams, the two laws, entropy.

Unit 2 · 5 labs

Electric Force, Field, and Potential

Charge, Coulomb’s law, electric fields and field lines, potential and potential energy, conductors and capacitors.

Unit 3 · 5 labs

Electric Circuits

Resistivity, Ohm’s law, power, series and parallel, Kirchhoff’s rules, capacitors, RC behavior.

Unit 4 · Planned

Magnetism & EM Induction

Magnetic fields, force on moving charges and wires, magnetic flux, Faraday’s and Lenz’s laws.

Unit 5 · Planned

Geometric Optics

Reflection, refraction, Snell’s law, total internal reflection, mirrors and lenses, ray diagrams.

Unit 6 · Planned

Waves, Sound & Physical Optics

Wave properties, superposition, standing waves, double-slit interference, diffraction, thin films.

Unit 7 · Planned

Modern Physics

Photons and the photoelectric effect, atomic energy levels and spectra, nuclear decay, mass–energy.

Interactive labs

Check against your syllabus

This unit list follows the 2024 redesign of AP Physics 2, which moved fluids to AP Physics 1 and starts the course with thermodynamics — seven units in all. Some teachers reorder units to fit the school year; if your class numbers them differently the content is the same, only the labels move.

How to use these notes

  1. Each unit is one lesson page. The contents panel on the left gives the study order; the formula sheet sits near the end.
  2. Work the numbered sections in order. Each ends with worked examples — try them before opening the solution.
  3. Do the lab. The exam asks experimental-design questions, and having actually taken the data makes those much easier.
  4. Come back to the formula sheet and check you can say what each symbol means and when the equation applies. That, not memorisation, is what the free-response section tests.

Calculus II for Engineers

Integration techniques, applications, infinite series, parametric and polar curves, and a first pass at differential equations — with every unit pointed at where an electrical engineer actually meets it. Partial fractions exist so you can invert a Laplace transform. Series exist so you can linearise a diode. Polar coordinates exist so you can read a Nyquist plot.

Units

Practice exams

What you need coming in

  • The derivative rules cold, especially chain rule and implicit differentiation. Integration is pattern-matching against derivatives you already know.
  • The Fundamental Theorem of Calculus, both parts, and what each is for.
  • u-substitution — the one Calc I technique you will use in every single unit.
  • Limits, including L’Hôpital’s rule. Half the series unit is limits in disguise.
  • Trig identities: Pythagorean, double-angle, half-angle. Unit 1 leans on them hard.
  • Algebra with exponentials and logs. ea+b = eaeb is not optional in EE.

Where each unit lands in the EE curriculum

UnitWhat it buys you
1 — Integration techniques Partial fractions is inverse Laplace. You will run it hundreds of times in Signals & Systems and Control Theory. Parts on eatcos bt is transient circuit response.
2 — Applications RMS voltage and average power. Every AC calculation, every spec sheet, every meter reading. Plus charge as ∫i dt and energy as ∫p dt.
3 — Series convergence Geometric series is feedback and the z-transform. Closed-loop gain, ladder networks, whether a discrete filter is stable.
4 — Taylor series Small-signal analysis. Every transistor and diode model is a first-order Taylor expansion about an operating point. Plus Euler’s formula, the whole basis of phasors.
5 — Parametric, polar, complex Impedance lives in the complex plane. Nyquist and polar plots, antenna patterns, Lissajous figures, roots of unity behind the DFT.
6 — Differential equations Every circuit with a capacitor or inductor is an ODE. RC time constants, RL current build-up, and the three damping regimes of RLC.
The three that get memorised wrong
  • ∫ sec x dx — the answer is a logarithm, not a power of sec. Nobody derives this mid-exam; memorise it.
  • ∫ dx/(a²+x²) has a 1/a out front; ∫ dx/√(a²−x²) does not. Losing that factor is the most common slip in Unit 1.
  • ∫ x−1 dx is the exception to the power rule. Applying xn+1/(n+1) here divides by zero.
How to work through it

Read the unit page, then close it and do the practice exam cold — no notes, timed. Grade honestly, and send every miss back to the section it came from rather than just reading the solution. Each question maps to exactly one section, which makes that loop fast.

Core antiderivative table

These are the ones you should recognize instantly, without deriving. Everything in Unit 1 is machinery for converting an unfamiliar integral into one of these. (Constant of integration omitted throughout.)

IntegralResultIntegralResult
∫ xn dx xn+1n+1, n ≠ −1 ∫ 1x dx ln|x|
∫ eax dx 1aeax ∫ ax dx ax / ln a
∫ sin x dx−cos x ∫ cos x dxsin x
∫ sec² x dxtan x ∫ csc² x dx−cot x
∫ sec x tan x dxsec x ∫ csc x cot x dx−csc x
∫ tan x dxln|sec x| ∫ cot x dxln|sin x|
∫ sec x dxln|sec x + tan x| ∫ csc x dx−ln|csc x + cot x|
∫ dxa² + x² 1a arctan(xa) ∫ dx√(a² − x²) arcsin(xa)
∫ sinh x dxcosh x ∫ cosh x dxsinh x
The three that get memorized wrong
  • ∫ sec x dx — the answer is a logarithm, not a power of sec. Nobody derives this mid-exam; memorize it.
  • ∫ dx/(a²+x²) has a 1/a out front; ∫ dx/√(a²−x²) does not. Losing that factor is the single most common arithmetic slip in Unit 1.
  • ∫ x−1 dx is the exception to the power rule. Applying xn+1/(n+1) here gives division by zero.

Calculus III for Engineers

Multivariable and vector calculus: the geometry of space, curves and motion, partial derivatives and optimisation, multiple integrals, vector fields, and the three big theorems that turn into Maxwell’s equations. Every unit is pointed at where an electrical engineer meets it — gradients give you E = −∇V, flux integrals give you Gauss’s law, Stokes’ theorem gives you Faraday’s. Every idea that needs spatial intuition has a 3D lab you can drive, in Interactive Laboratories.

Units

Practice exams

Interactive labs

What you need coming in

  • Calculus II — integration techniques above all. Multiple integrals are single integrals nested; the inner one still has to be done.
  • The chain rule, fluently. Unit 3 generalises it and Unit 5 depends on it.
  • Polar coordinates. Cylindrical is polar with a z bolted on; spherical is the 3D version.
  • Basic vectors — components, magnitude, dot product. Unit 1 rebuilds them, but the 3D vectors lab is the fastest refresher.

Where each unit lands in the EE curriculum

UnitWhat it buys you
1 — Vectors & geometryThe cross product is the Lorentz force and the Poynting vector. Cylindrical coordinates are coaxial cables; spherical are point charges and antennas.
2 — Vector functionsCharged-particle trajectories in E and B fields, and the paths every line integral runs along.
3 — Partial derivativesE = −∇V. Small-signal models are multivariable linearisation; tolerance analysis is the total differential.
4 — Multiple integralsTotal charge is ∭ρ dV; stored field energy and the capacitance of real geometries come from triple integrals.
5 — Vector fields & line integralsVoltage is a line integral of E. Path independence is Kirchhoff’s voltage law; Ampère’s law is a circulation.
6 — Surface integrals & theoremsFlux is Gauss’s law. The divergence and Stokes theorems convert all four Maxwell equations to differential form.
How to work through it

Read the unit page and play with every lab — drag the view, move the sliders, break the presets. Then close the page and do the practice exam cold, timed. Send every miss back to the section it came from; each question maps to exactly one section.

Coordinate systems and their volume elements

Every integral in this course is written in one of three coordinate systems, and the thing people forget is not the coordinates — it is the stretch factor that goes with them. Memorise this table; Unit 4 derives it, Units 5 and 6 use it constantly.

SystemCoordinatesConversion to CartesianVolume element \(dV\)Natural for
Cartesian \((x, y, z)\) — \(dx\,dy\,dz\) Boxes, planes, anything with flat faces
Cylindrical \((r, \theta, z)\), \(r \ge 0\) \(x = r\cos\theta,\; y = r\sin\theta,\; z = z\) \(r\,dr\,d\theta\,dz\) Cylinders, cones, paraboloids, coaxial cable, anything symmetric about the \(z\)-axis
Spherical \((\rho, \theta, \phi)\), \(\rho \ge 0\), \(0 \le \phi \le \pi\) \(x = \rho\sin\phi\cos\theta,\; y = \rho\sin\phi\sin\theta,\; z = \rho\cos\phi\) \(\rho^2\sin\phi\,d\rho\,d\theta\,d\phi\) Spheres, point charges, antenna radiation patterns, anything symmetric about a point
\(\theta\) is the same angle in cylindrical and spherical — measured in the \(xy\)-plane from the positive \(x\)-axis. \(\phi\) is measured down from the positive \(z\)-axis, so the equator is \(\phi = \pi/2\). Physics and EE texts swap the letters \(\theta\) and \(\phi\); check which convention your course uses.

The del operator, four ways

One symbol, \(\nabla = \langle \partial_x, \partial_y, \partial_z\rangle\), and the four things it can do. Units 3, 5 and 6 introduce them one at a time; here they are side by side so you can see the pattern.

OperationActs onGivesFormula (Cartesian)Meaning
Gradient \(\nabla f\) scalar field vector field \(\langle f_x, f_y, f_z\rangle\) Direction and rate of steepest increase. \(\mathbf{E} = -\nabla V\).
Divergence \(\nabla\cdot\mathbf{F}\) vector field scalar field \(\dfrac{\partial F_1}{\partial x} + \dfrac{\partial F_2}{\partial y} + \dfrac{\partial F_3}{\partial z}\) Net outflow per unit volume — source strength. \(\nabla\cdot\mathbf{E} = \rho/\varepsilon_0\).
Curl \(\nabla\times\mathbf{F}\) vector field vector field \(\begin{vmatrix}\mathbf{i}&\mathbf{j}&\mathbf{k}\\ \partial_x&\partial_y&\partial_z\\ F_1&F_2&F_3\end{vmatrix}\) Rotation per unit area — how a paddle wheel would spin. \(\nabla\times\mathbf{E} = -\partial_t\mathbf{B}\).
Laplacian \(\nabla^2 f\) scalar field scalar field \(f_{xx} + f_{yy} + f_{zz}\) Divergence of the gradient. \(\nabla^2 V = -\rho/\varepsilon_0\) (Poisson); \(\nabla^2 V = 0\) in empty space (Laplace).
The two identities that decide everything
  • \(\nabla\times(\nabla f) = \mathbf{0}\). The curl of a gradient is always zero. So a field with nonzero curl cannot be a gradient — it has no potential, and its line integrals depend on the path. This is why an induced electric field has no voltage function.
  • \(\nabla\cdot(\nabla\times\mathbf{F}) = 0\). The divergence of a curl is always zero. So a curl field has no sources — which is exactly the statement that magnetic field lines never begin or end.

AP Spanish Language and Culture

Exam preparation built around the four things the AP exam asks you to do: understand authentic print and audio Spanish, write a formal email and a source-based argumentative essay, hold a five-turn conversation, and give a two-minute cultural comparison. Units 2–4 cover every verb tense in Spanish; the task units run on the exam’s own clocks, with text-to-speech audio, a conversation simulator and self-recording built into the page.

Units

Practice exams

Reference

The exam at a glance

SectionWhat you doTimeWeight
I · Multiple choice65 questions on print, combined and audio sources~1 h 35 min50%
II · Task 1Email reply15 min12.5%
II · Task 2Argumentative essay from three sources~55 min12.5%
II · Task 3Conversation, five 20-second turns~5 min12.5%
II · Task 4Cultural comparison, 4 min prep + 2 min talk~6 min12.5%
How to work through it

Read each unit with the tools on — play the audio, run the drills, start the timers, record yourself. Then take the practice exam cold and timed, and score the speaking and writing against the rubric honestly. Keep a list of the mistakes you repeat; by spring that list is your review sheet.

Every verb tense, and where it is taught

Spanish has three moods and, counting the compound forms, eighteen tenses plus the imperative. You need to produce the first fifteen rows and recognise the rest. The verb tables conjugate all of them for 91 verbs.

MoodTenseEnglishExample (hablar)Unit
IndicativoPresentePresenthablo2
IndicativoPretéritoPreteritehablé2
IndicativoImperfectoImperfecthablaba2
IndicativoFuturoFuturehablaré2
IndicativoCondicionalConditionalhablaría2
IndicativoPretérito perfectoPresent perfecthe hablado3
IndicativoPluscuamperfectoPast perfecthabía hablado3
IndicativoFuturo perfectoFuture perfecthabré hablado3
IndicativoCondicional perfectoConditional perfecthabría hablado3
SubjuntivoPresentePresent subjunctive(que) hable4
SubjuntivoImperfecto (-ra / -se)Imperfect subjunctivehablara / hablase4
SubjuntivoPretérito perfectoPresent perfect subjunctivehaya hablado4
SubjuntivoPluscuamperfectoPast perfect subjunctivehubiera / hubiese hablado4
ImperativoAfirmativoAffirmative commandshabla, hable, hablemos, hablad, hablen4
ImperativoNegativoNegative commandsno hables, no hable, no hablemos…4
IndicativoPretérito anteriorPreterite perfect (literary — recognise)hube hablado3
SubjuntivoFuturoFuture subjunctive (archaic — recognise)hablare4
SubjuntivoFuturo perfectoFuture perfect subjunctive (archaic — recognise)hubiere hablado4
Plus the non-finite forms — infinitive hablar, gerund hablando, participle hablado — and the progressive (estar hablando) in every tense, all in Unit 3.

The six themes

Every source, prompt and conversation on the exam is drawn from one of six themes. You will not be told which one, and the cultural comparison can land on any of them — so Unit 5 gives you vocabulary for each and Unit 8 gives you ready-made cultural examples for each.

TemaThemeTypical contexts
Las familias y las comunidadesFamilies and communitiesFamily structure, traditions and values, education communities, citizenship, social networks
La ciencia y la tecnologíaScience and technologyAccess to technology, health and medicine, innovation, energy, the ethics of science
La belleza y la estéticaBeauty and aestheticsArchitecture, visual and performing arts, literature, ideals of beauty, fashion
La vida contemporáneaContemporary lifeEducation and careers, entertainment, travel and tourism, holidays, lifestyles, relationships
Los desafíos mundialesGlobal challengesEnvironmental, economic, political and social issues; health; population and demographics
Las identidades personales y públicasPersonal and public identitiesLanguage and identity, heroes and historical figures, nationalism, beliefs, alienation and assimilation
What each free-response task is really graded on
  • Email: did you answer every question, in usted, with a proper greeting and closing, and ask something back? Missing one of those caps the score no matter how good the Spanish is.
  • Essay: a clear thesis, and all three sources cited and used as evidence — not summarised. The audio source is the one people drop.
  • Conversation: a full answer to each turn, every time. Twenty seconds of on-topic Spanish beats five perfect words and fifteen seconds of silence.
  • Cultural comparison: a real comparison — both communities, similarities or differences, and the perspective behind the practice. Description alone tops out around a 3.

A study plan to May

Starting in late September leaves about thirty weeks. Run two tracks at once: one unit of structured study, and a daily fifteen minutes of real Spanish (a news clip, a podcast segment, an article) that keeps Section I stamina growing.

WhenStructured studyEvery week, alongside
Weeks 1–2Unit 1 — learn the exam; take Exam 1 cold as a baseline.15 min/day of listening or reading
Weeks 3–10Units 2, 3 and 4 — two to three weeks each; drills until 90%+ accuracy.One email reply (15 min)
Weeks 11–13Unit 5 — grammar in context and theme vocabulary.One email + one conversation
Weeks 14–18Unit 6 — one full timed essay per week.Conversation + cultural comparison
Weeks 19–23Unit 7 and Unit 8 — record yourself, score with the rubric.One essay every other week
Weeks 24–28Mixed review: retake Exams 1–8, one per week; re-study whatever scores lowest.All four tasks weekly
Last 2 weeksThe simulacro in one sitting; then the verb cheat sheets and your own error list.Light daily listening; sleep
How to work through this

Read a unit page with the tools switched on — press play on the audio, run the drills, start the timers, record yourself. Then close it and take the practice exam cold, timed, no notes. Score the free-response answers against the rubric honestly (listening to your own recording is uncomfortable, and it is the single most useful thing on this site). Keep a running list of the mistakes you repeat; by spring that list is your review sheet.

About the audio

Listening sources are read aloud by your browser’s built-in Spanish text-to-speech voice, so nothing is downloaded and every transcript is on the page. Synthetic voices are clearer and more even than real speakers — use them to learn the format, and use real Spanish media every day to get used to natural speed and accents. Recording works in any current browser once you allow the microphone; recordings never leave your device.

Physics II: Electricity & Magnetism for Electrical Engineers

Calculus-based electricity and magnetism, written for someone meeting it at university for the first time and heading into electrical engineering. Nine units take you from a single charge to the electromagnetic wave: fields, Gauss’s law, potential, capacitors, circuits, magnetic forces and sources, induction, and AC circuits with Maxwell’s equations. Every unit starts from intuition and pictures, points at where the idea shows up in EE, and comes with a lab you can drive and a timed practice exam.

Units

Practice exams

Interactive labs

What you need coming in

  • Calculus I and the start of Calculus II — derivatives, integrals, and setting up an integral by chopping something into small pieces. That last skill carries Units 1, 3 and 7.
  • Vectors — components, magnitude, dot and cross products. Every force and field here is a vector; the 3D vectors lab is a fast refresher.
  • Physics I mechanics — Newton’s second law, circular motion, work and energy. Charges in fields are just particles with a new force on them.
  • No E&M background needed. Unit 1 starts from what charge is.

Where each unit lands in the EE curriculum

UnitWhat it buys you
1 — FieldsEvery device is charges pushing charges. Fields are how you reason about it without tracking each one — from ESD to the inside of a transistor.
2 — Gauss’s lawShielding and conductors. Why the inside of a metal box is quiet, and the first of the four Maxwell equations.
3 — PotentialVoltage, defined properly. Every node voltage in every circuit is this quantity.
4 — CapacitanceEvery capacitor on every board, plus coax cables, MOSFET gates and DRAM cells.
5 — DC circuitsCircuit analysis — Kirchhoff’s rules and RC time constants are the core of Circuits I.
6 — Magnetic forcesMotors, speakers, Hall-effect current sensors and the physics of every CRT and mass spectrometer.
7 — Magnetic sourcesInductors and electromagnets — and why parallel traces carrying current push on each other.
8 — InductionGenerators, transformers, wireless charging and every inductor’s refusal to change its current suddenly.
9 — AC & EM wavesThe power grid, filters, tuned radios and antennas — Circuits II, Signals and Electromagnetics all start here.
How to work through it

Read each unit in order and stop at every figure until it makes sense — E&M is a subject you have to see. Drive the unit’s lab until the readouts stop surprising you. Then close everything and take the practice exam cold and timed; the scoring table at the end tells you which sections to go back to.