page_title: Teltron tube
section_title: Determination of the specific electron charge
hierarchical_section_title: Teltron tube / Determination of the specific electron charge
caption_attribution_description: English: Determination of the specific charge of the electron with the help of the filament beam-test Deutsch: Bestimmung der spezifischen Ladung des Elektrons mit Hilfe des Fadenstrahlrohr-Versuchs, selbst erstellt (original)
context_page_description: A teltron tube is a type of cathode ray tube used to demonstrate the properties of electrons. There were several different types made by Teltron including a diode, a triode, a Maltese Cross tube, a simple deflection tube with a fluorescent screen, and one which could be used to measure the charge-to-mass ratio of an electron. The latter two contained an electron gun with deflecting plates. The beams can be bent by applying voltages to various electrodes in the tube or by holding a magnet close by. The electron beams are visible as fine bluish lines. This is accomplished by filling the tube with low pressure helium or Hydrogen gas. A few of the electrons in the beam collide with the helium atoms, causing them to fluoresce and emit light.
  They are usually used to teach electromagnetic effects because they show how an electron beam is affected by electric fields and by magnetic fields like the Lorentz force.
context_section_description: The higher the coil current, the stronger magnetic field and thus smaller radius of the circular path of the electrons. The strength of the magnetic field and the Lorentz force are proportional to each other, such that when the Lorentz force increases. A larger Lorentz force will deflect the electrons more strongly, so the orbit will be smaller. The Lorentz force  is always perpendicular to the instantaneous direction of movement and allows a centripetal  circular motion. The magnitude of the velocity and hence the kinetic energy can not change:
  From this we get the amount of specific electron charge
  The determination of the velocity is performed using the energy conservation law
  This is finally followed by
  The specific electron charge has the value
  Since the charge of an electron is available from the Millikan experiment, the study of electrons in an magnetic field is the determination of its mass in accordance with:
  Similar concepts for the weighing of charged particles can be found in the mass spectrometer.
caption: Derivation of the formula to determine the specific charge of the electron with the help of the filament beam-test
exif: {}