Evaluation of the Lorentz law by using a Barlow wheel

In this work, an evaluation of the Lorentz law has been carried out by a Barlow wheel. Basically, a Barlow wheel is a primitive dynamo-electric machine (invented by P. Barlow in 1828) which consists of a metallic cogwheel, which moves around a horizontal axis. The theoretical analysis includes the Lorentz law and the Petroff law, which characterizes the friction between the axis and the bearing. In the stationary state (when the angular velocity is constant), a simple formula can be obtained which relates the current intensity and the angular velocity. Experimental data approximately confirms this formula, and this device can be used as a simple and classical laboratory experiment in basic electromagnetism courses. Some modern complements were used for the acquisition of data, as a light barrier connected to a counter, a voltammeter and a direct-current power supply Therefore, the Barlow wheel, originally designed for qualitative demonstrations, can be used as a quantitative and useful assembly in a laboratory of General Physics.