The Perrin tube may be used to show that charge can be accumulated in the Faraday pail incorporated, that the charge does not disappear when the filament is switched off and therefore that the cathode rays must consist of charged particles. Electron deflection sensitivity may be measured using Helmholtz coils to deflect the beam.
Cathode ray tube operation may also be demonstrated, using a ‘secondary coil’ for the transverse field. The tube comprises a standard spherical glass body with a cylindrical neck containing a diode electron gun with filament and cylindrical anode, and a Faraday’s pail in the sphere, at 45° to the axis. Connections to the diode electron gun are via 4mm sockets in the moulded cap and the Faraday’s pail connection is via a 4mm plug in one of the side caps. The end of the sphere has an internal phosphor coating providing a luminescent screen.
• Maximum filament voltage: 7.5V.
• Anode voltage: 2000 to 5000V.
• Typical operation at 4000V: anode current 1.8mA beam current 4μA.
Supplied complete with instructions.