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One of the more ‘practical’ experiments done in advanced physics labs is where a cathode ray tube (which shoots electrons) is surrounded by a magnetic field. By changing the magnetic field you manipulate the path of the electrons and cause them to strike the end of the tube in different areas. By measuring the change of path you could measure the field or calculate the deflection if you knew the power of the magnetic field. The experiment is considered practical because it doesn’t take much to realize this is how old TVs and Computer monitors worked (before LCD screens became the default). The experiment is only a crude imitation of the process that goes on in a TV, but it at least gives you the idea.

The biggest issue with the experiment is that it needed a lot of stuff to work. Cathode Ray tubes were purchased separately, as were the field generating coils, wires, power supplies, variacs, it made quite a mess. Some ‘kit’ versions were produced but none were as convenient as United Scientific’s Complete Properties of Electrons Apparatus


This electron properties lab is base on a 75mm flat screen CRT, and it contained in a compact metal case with a removable lid. All the accessories needed to explore electrostatic deflection, focusing, and electron behavior in a transverse and axial magnetic field is included. The power supply and measurement 2479acircuitry is entirely enclosed for safety and reliability. Multi-turn potentiometers and three 3-1/2 digit LED meter displays help students easily obtain precise results. A full operator’s manual with experiment descriptions is included, and explains both background and procedures, including the determination of e/m using the focusing effect of an electron beam spiraling around an axial magnetic field.

2479bThe CRT is a 14 pin tube, 240mm long with a 75mm diameter round screen. A separate transparent screen grid is provided for quantitative measurement. The tube operates on 900-1450V and includes electrodes for electrostatic focusing and for electrostatic deflection in the horizontal and vertical directions.

The power supply and control system provides the voltages to operate the tube, and and the focusing and acceleration potentials can be set and monitored separately. Coarse and fine adjustments are provided, Similarly, the electrostatic deflection in each direction can be separately set and monitored. A further section provides power for the transverse and axial magnetic field coils.
The magnetic field coils supplied include a pair of 530-turn coils of 30mm mean diameter for the transverse field and a 1300-turn solenoid of 95mm diameter for the axial field. The transverse field coils plug directly into sockets in the base, and the axial field solenoid firs over the CRT and is connected to the base by a pair of supplied patch cords.

The Complete Properties of Electrons Apparatus is built-on-demand and may take up to 90 days to ship due to its construction time. Please contact us at sales@spectrum-scientifics.com for more information about build-times, etc.

Want to buy the Complete Properties of Electrons Apparatus?

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