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 explain things to you as 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 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. I started my career designing integrated circuits and computers for TRW and Hewlett-Packard. Later on I got to work at Agilent Technologies, and then two exciting medical device startup companies.

I had a great year as a Content Fellow at Khan Academy. Sal and the other content creators taught me the approach to teaching in the KA style.

Here at Spinning Numbers I have been improving the articles I wrote for KA based on questions from learners, and writing new articles as well. The videos are the same videos you see on the KA EE site.

All through my career, for each new project I would go back to my college textbooks to re-study the fundamentals I needed. Years after graduation there were moments 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.

It’s is all a labor of love.

Circuit sandbox

Circuit simulation is a critical tool for engineers. A special feature at Spinning Numbers is the Circuit sandbox simulator. You can study circuits by simulation and try out your own ideas.

Creating the site

This site is saved at GitHub, hosted by GitHub Pages. The site is generated by Jekyll using the ‘minima’ theme. GitHub provides a free ssl security certificate (https) to protect user information.

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.

Comments are implemented with Staticman, with protection from robots provided by reCAPTCHA.


If you contribute a question, comment, or reply, you can optionally enter your email address to be notified of new comments. The notification email is sent by Staticman using a secure private email service provider, MailGun. Your address will only be used for notifications. You may unsubscribe at any time.


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