This magnet (seen at 3:15) is crazy. A smaller version is demonstrated at 6:30, they are dropping an aluminum tube through the magnetic field demonstrating Lenz’s Law, we saw Lenz’s Law in action here but the results are a bit more impressive with a super huge magnet!
You have probably used some Lithium Polymer batteries in some of your projects or toys. They pack a bunch of power in a small package (they can also be a bit dangerous if not handled correctly). Our friend Csaba has built a Lithium Polymer Internal Resistance Meter that will let you measure the resistance of the battery which is a good way to determine how good the battery is.
