e/m Apparatus

Perform accurate measurements of the charge-to-mass ratio of the electron. Includes power supplies which can also be used in other experiments.

WHAT'S INCLUDED

• 1x Helmholtz coils for e/m

• 1x Replacement e/m Tube

• 1x Tunable DC Power Supply (Constant Current)

• 1x DC Power Supply II (Constant Voltage)

• 1x Red and Black Patch Cords
  
  How It Works
  

  A large, helium-filled electron tube is mounted between a pair of Helmholtz coils. The tube contains an electron gun, which generates a focused beam of electrons. A measured current is applied to the Helmholtz coils so that the magnitude of the magnetic field within the electron tube can be calculated. A measured accelerating potential (V) is then applied to the electron gun. The magnetic field (B) deflects the electron beam in a circular path with a radius (r) that is measured using the illuminated mm scale. From these measured values, the charge-to-mass ratio of the electron is calculated:
  e/m = 2V/B2r2. (The details of the calculations are fully described in the manual.)