Objective: Determine the polarity of the charge-carriers
In the Perrin tube, the electron beam can be deflected into a Faraday cup by applying a homogeneous magnetic field. The charge of the electrons can be observed by connecting an electroscope to the Faraday cup, and its polarity can be determined by comparison with an electric charge of known polarity.
![Experiment: Perrin tube (115 V, 50/60 Hz), 8000663 [UE3070400-115], Electron tubes](/imagelibrary/UE3070400-115/UE3070400-115_01_Experiment-Perrin-tube-115-V-5060-Hz.jpg)
![Experiment: Perrin tube (115 V, 50/60 Hz), 8000663 [UE3070400-115], Electron tubes](/thumblibrary/UE3070400-115/UE3070400-115_01_1200_1200_Experiment-Perrin-tube-115-V-5060-Hz.jpg)
