Experiment: Perrin tube (115 V, 50/60 Hz)

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Description
Delivery scope

Thematic focus:_..

• Observing the thermionic emission of charge-carriers from a heated cathode.
• Determining the polarity of the emitted charge-carriers.
• Estimating the specific charge (chargeto-mass ratio) of the charge-carriers.

Experiment description:_..

In the experiment, the electron beam is deflected by the homogeneous magnetic field of a Helmholtz coil pair into the Faraday cup, which is connected to an electroscope. From the observed charging or discharging of the electroscope by the electron beam entering the Faraday cup, it is possible to determine the polarity of the charge-carriers
It is also possible to estimate the specific charge of the charge-carriers, since the radius of curvature r of the curved path into the Faraday cup is known. The centripetal force acting on the charge-carriers in this curved path is given by the Lorentz force.