Version Log

From Fundamentals to AI Apocalypse · newest first

What changed on the site and when. Chapters are added as the semester's lectures arrive; each version groups the changes released together.

2.24 Coordinate systems appendix

10 November 2026

EEI has an Appendix tab with its first page, Appendix A: Coordinate systems. It gathers the course’s coordinate formula sheet in one place, rearranged and explained: Cartesian, cylindrical and spherical coordinates with their ranges, unit vectors and cross products, every unit-vector conversion (including between cylindrical and spherical), the position vector, and the path, area and volume elements, with quick checks such as the area of a sphere.
New 3D figures show a point in cylindrical and in spherical coordinates with its unit vectors and area patch, and the Cartesian volume element with the normal of each face. A short table says which system suits which problem, and three common slips are spelled out. A PDF and LaTeX download come with it.

2.27 Tutorials to standard

10 November 2026

EEI Tutorials 1–6 were reviewed against the course sheet; every result was re-derived and is correct. Two direction sentences in Tutorial 3 were wrong and are fixed (F₁₂ points up and to the left; Q₃ lies left of Q₂), and Tutorial 5 now writes the potentials as φ_e, so φ means only the angle.
Every worked line uses the site’s maths: stacked fractions, roots with their bar, one integral style and variables in italics. Tutorial 2 links to charge densities (§1.6) and to Appendix A for the volume elements.
New figures drawn for the tasks: P₁, P₂ and their displacement in 3D, the hollow cylinder and the shell of a charged sphere, the line and point charges with their distances, both capacitor stacks with their equivalent circuits, the two-dielectric coaxial field, and the conductor sector from above. The Task 7 figure no longer gives away where Q₃ is.
On phones, long worked lines now wrap inside their frame on every exercise and tutorial page instead of running off the screen, also in Safari.

2.26 EEI Tutorial 6

10 November 2026

Added step-by-step solutions for stationary radial current through a two-conductivity annular sector, including interface conditions, current density, field, voltage and resistance.

2.25 EEI Tutorial 5

10 November 2026

Added step-by-step solutions for the coaxial capacitor with two angular dielectric sectors, including the radial field, interface conditions, charge–voltage relation, capacitance and numerical value.

2.23 EEI Tutorial 4

10 November 2026

Added step-by-step solutions for the two-layer plate capacitor, including fields and surface charge, its initial series model, the shifted dielectric’s series-parallel model, the capacitance formula and its extrema.

2.22 EEI Tutorial 3

10 November 2026

Added step-by-step solutions for the point and infinite-line charge force arrangement, and for recovering the third point charge’s location, sign, ratio and net force from supplied resultants.

2.21 EEI Tutorial 2

10 November 2026

Added step-by-step solutions for total charge in a uniformly charged hollow cylinder and a sphere with radially varying density. The tutorial is linked from the EEI Tutorial tab with connections to Chapter 1 coordinate and Gauss-law topics.

2.20 EEI Tutorial 1

10 November 2026

Added step-by-step solutions for Tutorial 1’s SI-prefix conversions, Cartesian vectors, spherical-coordinate conversion and unit-vector table. The tutorial is linked from the EEI Tutorial tab and connects back to relevant Chapter 1 topics.

2.19 Cleaner diagrams

9 November 2026

Arrowheads grow with their line, so thick arrows end in a sharp point instead of a blunt stub, and the mapping arrows no longer end in oversized heads.
Plotted curves and field lines are drawn smooth, without kinks between sample points; the potential and field plot in EEI Chapter 1 has more points near the charge.
Labels no longer sit on lines, curves or rings: the Gaussian surface, superposition, unit circle, polar coordinates and function-test plots in the guides, and the exercise figures (loop, charged sphere, half-space, two-dielectric coaxial capacitor). Unit vectors read e_z, e_ρ, e_φ with real subscripts, and the “+” and “−” above capacitor plates are no longer cut off.
On phones, step charts (such as the induction chain) stack top to bottom so their text stays readable. The PDFs carry the same fixes.

2.18 Exercise pages fit the site

9 November 2026

Exercise pages use the same side bar as the study guides: the site mark, the fold button, the Chapters list (which now includes each subject’s exercises) and section highlighting as you read. Previous and Next exercise links close each page.
On the home page, the Exercise tab lists exercises as rows like chapters, each with what it covers and a Worked solutions button. The count under the subject name folds whichever tab is open (“2 chapters”, “4 exercises”), and each subject remembers the tab you chose.
Lecture, Exercise and Tutorial form one switch like Guide | Lab on the guides. Exercise rows get route stops like chapters, every stop sits on its row number (on phones too), and when a subject’s chapters are folded or another tab is open the route ends on a stop at the subject.
On phones, worked-solution lines break before an = sign instead of between a minus and the fraction it belongs to.

2.17 EEI exercise review

9 November 2026

EEI Exercise 4, task 10b: the voltage now runs the way the sheet defines it, from the outer cylinder to the inner one (U₂₀ = φ₂ − φ₀). For positive U₂₀ the field points inward and σ₀ is negative; the earlier version had every sign flipped. The capacitance is unchanged.
EEI Exercise 3, task 8d: the full energy balance when the dielectric is pulled out at fixed voltage, including the energy returned to the source and the mechanical work needed.
EEI Exercise 2: the actual force sizes in task 4, and the from-infinity reading of task 6c.
EEI Exercise 1, task 1a: the surfaces as position vectors, and why φ hides in the direction of e_ρ.
All four EEI exercise solutions set fractions top over bottom instead of with a slash, and every integral sign is stacked with its limits; brackets around a fraction grow to fit it, on the page and in the PDF, and ln, sin and cos are set as proper function names in the PDF.

2.16 APDR Chapter 4 corrections

9 November 2026

Clarified the IEEE overflow result by rounding mode and corrected special-arithmetic examples for infinity and signed zero.
Refreshed the generated Chapter 4 LaTeX and PDF from the HTML source.

2.15 EEI Exercise 4

6 November 2026

EEI Exercise 4: step-by-step solutions for dielectric boundary conditions and a two-layer coaxial capacitor, with matching browser/PDF diagrams and links to Chapter 1 topics.
Exercise 3 review: clarified that the capacitor energy change is measured in joules.

2.14 EEI Exercise 3

6 November 2026

EEI Exercise 3: step-by-step solutions for Gauss’s law with a charged sphere and a composite dielectric capacitor, with matching page/PDF diagrams.
Exercise 2 results now state the SI units for fields, forces and work.

2.13 EEI Exercise 2

6 November 2026

EEI Exercise 2: seven step-by-step solutions for Coulomb force, superposed fields and square-corner charges, with two diagrams and topic links.

2.12 Course parts and worked solutions

5 November 2026

Subject pages now switch between Lecture, Exercise and Tutorial resources, with a clear message when a part has no material yet.
EEI Exercise 1 explanations now show each setup and reasoning step, connect the problems to related EEI topics, and include three diagrams on the page and in the printable PDF.
Key equations are separated from prose and use the project’s math serif in both the page and PDF.

2.11 EEI Exercise 1

5 November 2026

EEI Exercise 1: step-by-step solutions for the cylinder surfaces, hemisphere area and volume, and three circular field integrals.

2.10 Current flow lab

5 November 2026

EEI Chapter 2: six interactive predict-then-reveal experiments for current flow, conductor response, resistance and tolerance, interfaces, power, and energy.

2.9 Stationary currents

5 November 2026

EEI Chapter 2: a new study guide for current density, Ohm’s law, material interfaces, resistance, energy and power.

2.8 Freer labs

4 November 2026

Something new at the very bottom of the home page. Scroll all the way down.
Lab progress fix: an experiment whose challenges are all answered now counts on the home page even if you left or reloaded before pressing “Open the sandbox”. Opening the lab again restores any experiment that was missing. Ticking a guide skill no longer erases lab progress made in another tab.
EEI Chapter 1 guide: the professor fixed most of the slips we reported in the revised script, so “Slips in the notes” now lists only the three that remain (p. 47 notation, the swapped voltage names on pp. 84 and 90, and p. 92).
Bit patterns can be clicked: under every bit field in APDR 3 (encodings, unsigned and signed sums), APDR 4 (binary fractions, the IEEE exponent and fraction) and APDR 34a (binary sums, fraction decoding), a row of cells flips one bit per press and the result follows.
APDR 2 lab: type your own umbrella rule in C, W and R and see on which rows it differs from C′·(W+R); build any NAND-only circuit such as NAND(NAND(A, A), NAND(B, B)) and see its truth table, its name and how many gates it uses.
APDR 12a lab: type any function of A, B and C and pick any of the six variable orders to count its reduced OBDD nodes; set the two path delays in the hazard experiment and watch the gap open or close.
EEI Chapter 1 lab: save your charge layout and restore it on a later visit; the charge dropdowns use the site’s own list.
APDR labs show results as you type: the Convert, Decode, Calculate and Evaluate buttons are gone in APDR 2, 3, 4, 34a and 5, and each sandbox opens with its result already worked out.
APDR 12a lab: type both sides of your own identity in x and y and compare the rows; type minterms and don’t-cares or click Karnaugh-map cells (0 → 1 → d); type a truth table or click the f row to get its algebraic normal form.
Lab controls: dropdowns open the site’s own list instead of the browser’s, and every dropdown and typed field has the same box and width, so the controls line up.
Every lab experiment has an Explore freely button: open the sandbox at any time, then go back to the waiting challenge.
Lab fixes: the EEI point-charge sandbox opens with a charge instead of an empty field; sliders no longer stick out of the EEI controls; the duplicate slider strips on the MEI 2 and 3 stages are gone, which also uncovers the Pascal caption; labels sit next to their controls; tall APDR stages centre their drawing.
New challenge: after an experiment’s fixed challenges, thirty-five experiments generate fresh questions with computed answers, as many as you like: truth-table counts and set operations (MEI 1); binary values, distance intervals and binomial coefficients (MEI 2); mapping types, linear inverses, compositions and polar coordinates (MEI 3); base conversion, two’s-complement decoding, ASCII letters, binary addition and signed overflow (APDR 3); address bits, byte order and interleaving (APDR 5); square-root steps, the umbrella rule and NAND circuits (APDR 2); float spacing, binary fractions, multiplication, exponent bias and special values (APDR 4); identity checks, Karnaugh-map covers and algebraic normal forms (APDR 12a); integer encodings, binary sums, spacing, fractions and IEEE decoding (APDR 34a); plate-capacitor changes and series or parallel capacitors (EEI 1). Practice questions do not change your saved results.
APDR guides gain diagrams: flowcharts of an iteration, the stored-program machine and the three program checks; De Morgan Venn diagrams; gate-delay and static-1-hazard waveforms; Karnaugh maps with a group of four and a wrap-around group; 'A' in ASCII bits; the 4-bit two’s-complement wheel; floating-point gaps doubling; +0, +∞ and NaN bit patterns; a C pointer and two Python names for one list as memory boxes; a 16-bit address.
MEI 1 lab: type any logic formula in A, B, C for its truth table and verdict, or a set expression over your own X, A and B. MEI 2 lab: type any bits (up to 10), any centre and radius, any Pascal row up to 12.
MEI 3 lab: type your own rule in every experiment (mapping with your own sets, inverse test with a draggable horizontal line, composition of two rules, any graph) and drag the polar point.
MEI guides gain diagrams: implication and De Morgan as Venn diagrams, nested number systems, Pascal’s triangle, induction as a chain, the vertical-line test, f and f⁻¹ mirrored in y = x, the discriminant’s three cases, and e^x against ln x.
EEI Chapter 1 gains diagrams: like and unlike charges, adding fields at a point, dipole field lines, equipotentials, a Gaussian surface, a dielectric slab, potential against field, and the charging triangle.

2.7 Easier to follow

4 November 2026

Every study guide now reads on its own: each section opens with the idea in plain words before any symbols.
Formula cards that introduce notation say how to read them aloud, for example “the image of f is the set of all f(x) as x runs through X”.
In MEI Chapter 3, arrow diagrams show mappings, injective and surjective, inverses and composition, with the part that matters highlighted, on the page and in the PDF.
Each section has a near miss: an example that almost fits the definition and fails, with the reason.
Diagrams across the guides, on the page and in the PDF: Venn diagrams for sets and logic, number lines for intervals and bounds, bit-cell pictures for place values, two’s complement, IEEE 754, byte order and interleaving, the unit circle, field lines, and the memory hierarchy.
Formulas are spaced the way a book sets them (x ∈ A, (x, y), X × Y), and sub- and superscripts are larger.

2.6 HUD layer

4 November 2026

A radar in the hub header shows each chapter you have started as a contact; the sweep passes over them.
Headings decode into place the first time they come into view, sweeping across the line.
A reading chip at the top of the page shows the section you are in, how far through it you are and the minutes left.
Formula cards, worked examples and recall checks have corner brackets; signal lines have a soft glow.
The reading column is wider, headings that nearly fit one line are fitted to it, and every line in a section ends at the same edge.
Formula cards never scroll sideways: long formulas break before a relation sign instead. A symmetric settings gear, and no sideways scrolling on phones.
The contents rail folds away to a slim strip on wide screens, and the site remembers it.
Reading columns, cards and chapter buttons sit centred, with equal space on each side.
New pages: How to use, and this version log.

2.5 Settings and folding

4 November 2026

Settings: theme (System, Light, Dark), motion (System, Reduced) and text size (Default, Large).
A ring marks the furthest chapter you have reached, and a signal travels down the route ahead.
The hub's subjects and the not-yet-due board rows fold, and remember how you left them.
APDR and EEI formula cards use the same notation as the maths guides.

2.4 Motion and navigation

3 November 2026

Page changes sweep in, and a reading-progress bar runs along the top of each guide.
The hub route lights up as you start chapters, and skill bars fill as you tick.
Worked examples can be stepped through, symbols trace through a section on hover, and the concept map shows direction.
The contents rail folds, follows your reading position, and lists every chapter; a phone gets a Contents bar.
Lab challenges animate step by step and answer buttons respond when pressed.

2.3 MEI and APDR Chapter 5

3 November 2026

New guides and labs: MEI Chapters 2 and 3, and APDR Chapter 5.
MEI Chapter 1 lab: tautology, unique existence, sensor vote and interval experiments.
Notes reviews for MEI Chapters 1 to 3 fixed slips, added missing topics and computed the lab keys.
Sum, product, integral, union and intersection limits are stacked properly on the site and in the PDFs.
Better phone layout and dark-mode lab controls; every page and PDF credits the author.

2.2 APDR guides complete

1–3 November 2026

APDR study guides and interactive labs for Chapters 12a, 3, 4 and 34a.
Improved study flows in guides and labs, and review fixes to wording, lab keys and checklist totals.

2.1 First APDR chapter

29 October 2026

APDR Chapter 2 study guide and lab.

2.0 Redesign by semester

27–28 October 2026

The site is reorganised by semester and subject, with the animated site mark.
EEI Chapter 1 study guide and lab, written to a shared guide standard and lab standard.
Concept maps in guides.

1.0 First release

22 October 2026

The first electrostatics and maths guides and labs, published on GitHub Pages.

New to the site? Start with How to use. Made by Thanate Amornjiraporn (Focus).