Welcome to Spinning Numbers! Learn about the world of electricity and electrical engineering. The concepts are taught at the level of an undergraduate EE student.

Circuit sandbox

The shiny new feature of Spinning Numbers is a circuit simulator, the Circuit sandbox.
Run the Circuit sandbox in English or Circuit sandbox en Español.


Become familiar with the most important electrical quantities: charge, current and voltage.

Circuit elements

Circuits are made of resistors, capacitors, inductors, and voltage and sources.

Circuits with resistors

Resistors in series and parallel, delta-wye networks, and the voltage divider.

DC circuit analysis

Find the currents and voltges of a DC circuit. Kirchhoff’s Laws, node voltage method, mesh and loop current methods. Linearity and superposition.

What’s with the name?

Where does the name Spinning Numbers come from?


Here’s a list of new material created for Spinning Numbers you won’t find on KA.


A collection of interesting questions and answers about electrical topics.

Coming soon

Basic circuit analysis

Find the state of a DC circuit using Kirchhoff’s Laws. The node voltage method, mesh current method, and loop current method.

Circuits with capacitors and inductors

Natural and forced response of RC, RL, and RLC circuits. This is where we start to use calculus.

AC circuit analysis

We confine signals to only sine waves, and then develop an analysis method using complex exponentials. These methods are much simpler than solving differential equations from scratch.

These videos and articles got their start at Khan Academy where I was the Electrical Engineering Content Fellow in 2016. I hope you enjoy them.

  • Willy McAllister