Electrical Engineering Fundamentals · interactive
Companion to the Purdue University Press textbook

Stop reading about circuits. Start turning the knobs.

The textbook is free and open. This site is where you use it — every chapter gets circuits you can change, breakers you can trip, and practice problems that generate fresh numbers every time so you can't memorise your way out.

Start Chapter 1 → Get the free book
Voltage is always blue Current is always orange Power is always aqua

Consequences, not answers

Switch on the hair dryer and the breaker actually trips. Short out a branch and watch the power stop reaching three elements. The circuit reacts, so the rule sticks.

New numbers, every time

Every drill regenerates its own values. You can run the same exercise ten times and get ten genuinely different problems — the way practice is supposed to work.

Signs made visible

The book warns that ignoring direction and polarity “is the cause of many sign errors.” So the exercises here mark where your sign went wrong, not just that it did.

Study companion · account required

Chat with the book

Stuck on a sign convention at midnight? Ask. The companion answers from this textbook and nothing else — it draws the circuit, writes the equation out properly, and hands you a practice question to check whether it actually landed.

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Accounts are approved by hand, so requesting one takes a moment longer than signing up elsewhere. Running the assistant costs real money, and that keeps it sustainable and free to use.

What it does
Draws the circuit
Schematics in the same hand as the rest of the site — polarities and current directions marked, because that is where the marks are lost.
Sets the maths properly
Real fractions, subscripts and integrals — p = vi, not p = v*i.
Quizzes you back
Questions you answer in place, marked instantly, with the reasoning behind every wrong option spelled out.
voltage current power

The thirteen chapters

Chapter 1 is live now. The rest follow the same shape: a short recap of what you need, then a set of interactives — simulators to build intuition, drills to build speed.

The source text

Electrical Engineering Fundamentals

Maryam A. Al-Othman, John H. Cole, and Dimitrios Peroulis · Purdue University Press, 2025

The textbook for ECE 20001 at Purdue University. Its authors decided it should be free for everyone — this companion follows the same principle. Nothing here replaces the book; it gives you somewhere to put the ideas to work.