Welcome to Spinning Numbers. The topics covered here are what you will find in an undergraduate electrical engineering course on circuits. My goal is to talk to you like a good friend who wants to help you understand these elegant ideas.

I got interested electricity when I was about eight years old. My first sense of wonder came from a tube radio. This glowing little box played music sent on invisible waves from miles away. Are you kidding me! How great is that! How did someone figure that out? Electricity is invisible, and yet people understand it, and can invent radios and other great stuff. I wanted to understand, too.

In college my major was electrical engineering. After graduating I started my career designing integrated circuits and computers. For each new project I would go back to my textbooks to re-study the fundamentals I needed. Years after graduation there were moments where I would slap my head and say, “So that’s what my teacher meant!” I hope these videos and articles help you to have similar head-slapping Aha! moments, but without the long years in between.

The videos and articles you find here started life when I was at Khan Academy in 2015-16. I was the Content Fellow for Electrical Engineering. Sal and the other content creators taught me how to approach teaching in the KA style.

I have been adding new material and improving the articles I wrote for KA based on questions from learners, and writing new articles as well. The video links go to the same videos you see on the KA EE site. It’s is all a labor of love.

Circuit sandbox

Circuit simulation is a critical tool for all engineers. A special feature here at Spinning Numbers is the Circuit sandbox simulator. You can study circuits and try out your own ideas. The simulator is something I wanted to make available on Khan Academy but didn’t have the time during my fellowship.

Creating the site

This site is saved at GitHub, hosted by GitHub Pages. The site is generated by Jekyll using the ‘minima’ theme. Github

The articles are written in Jekyll’s Kramdown superset of Markdown.

Equations are rendered by $\KaTeX$, the super-fast math typesetting library from Khan Academy.

Drawings of circuits and other images come from Adobe Illustrator and Inkscape.

Animated images and computed graphs are created with D3.js. The source code for animations and graphs are in the /assets/d3 folder.

Videos are drawn in Sketchbook Pro. The screen and audio are captured and edited in Camtasia. I use a Wacom Bamboo tablet, and a Sampson USB microphone.

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I’m grateful to Sal Khan and everyone at Khan Academy for the inspiring vision of a free world-class education for anyone, anywhere.