You put your phone down on a pad. Nothing touches. And it starts charging.

How does that actually work?

In this episode Daniel asks the question the second he hears the charging chime — and what he and Mom figure out together goes from a coil of wire in your charging pad all the way to Nikola Tesla's unfinished tower on Long Island, electric cars charging while they drive, and a scientist named Faraday who figured out the whole principle almost two hundred years before smartphones existed.

Here's what's actually happening when you place your phone on a wireless charger. The electricity stays in the wires. What crosses the gap is a magnetic field. Inside the charging pad there's a coil of wire, and when electricity runs through it, a magnetic field appears around it. Your phone has its own coil inside it. When that coil sits insi ...