A Nontoxic Barlow's Wheel
Barlow's wheel has been a favorite demonstration since its invention by Peter Barlow (1776–1862) in 1822.1 In the form shown in Fig. 1, it represents the first electric motor. The interaction between the electric current passing from the axle of the wheel to the rim and the magnetic field produced by the U-magnet produces a torque that turns the wheel. The original device used mercury to provide electrical contact to the rim, and the dangers involved with the use of this heavy metalhave caused the apparatus to disappear from the lecture hall.
“A Non-Toxic Barlow’s Wheel”, The Physics Teacher, 53, 42-43 (2015) (with John Daffron)
The Physics Teacher