• Measures the charge to mass ratio of the electron
• Internal computer control of voltage and current
• Unit construction with power supplies in the base
• Large Helmholtz coils for uniform magnetic field
This classic experiment consists of a vacuum tube within which an electron beam forms, mounting inside a pair of Helmholtz coils providing a transverse field. The electron gun points downward, and the magnetic field bends the electron beam into a circular path. The beam is made visible by placing a little helium gas at low pressure in the vacuum tube. The gas glows when struck by the electrons.
The accelerating voltages vary from 100 to 500 VDC so students can study a wide range of electron velocities. The Helmholtz coil current adjusts to modulate the bending force on the electron beam. The orbit diameter is measured on an internal glass scale with fluorescent scale marks. The mark lights up when the beam strikes ist, making it easy to determine the exact beam diameter. Two panel knobs set the accelerating voltage and coil current. A pair of three-digit panel meters monitor the power supplies.
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