Nested brass cups rotate relative to each other. The friction between the two is converted to heating of the cups and their contents. A spring balance and counter aid in determining the amount of work done when you turn the crank.

Not suitable for a complete experimental lecture demonstration due to the amount of time required to get useful data.

This demo can be found in cabinet D on shelf 5 of the UCSD PUL Demo Room (WLH 2015).