Measurement of e/m for Electrons
Friday, Section 006
KONSTRUERA: Yilikal Ayino
with Kevin Haar & Gregory Overdorf
February 28, 2014 PreLab
By Cambridge School in 1897, J. J. Thomson researched the mystical " corpuscles” of the rays emanating from your cathode of any cathode ray tube. Employing knowledge of the Lorentz push, Thomson scored the charge-to-mass ratio of such corpuscles, which usually we now find out as electrons.
A slightly modified version of Thomson's test using (essentially) a cathode ray tube will be described here. A cathode ray tube (CRT) is a great evacuated circular glass step containing a great electron gun and increasing electrode discs. The CRT is filled with a bit of a respectable gas, which usually when ionized by a completing electron, glows along their path. The electron firearm is an indirectly warmed barium oxide-coated cathode having a Wehnelt cylinder at adverse potential for centering the emanating rays in a nearby valve with a pit in this. The electrons are more rapid from the cathode, focused right into a helix, through the hole inside the anode (at positive potential—creating an electric field), thus growing with kinetic energy, K, equal to the item of the electron's charge, e, and the volts, V (potential difference). Supposing they are released with negligible energy,
wherever m is a mass of the electron, in such a case. After growing from the hole in the positive elektrode, the electrons enter a region with no electric power fields, for that reason then journeying at a consistent velocity. The beam's way is illuminated due to the ionization of the gas.
A magnetic discipline is applied to the light beam using Helmholtz coils. Helmholtz coils are two vertically orientated, similar circular coils of line (solenoids) which might be placed parallel to each other, symmetric along a shared axis, one to each side with the domain with the experiment. You will discover equal currents flowing in the same path in each coil. The distance, d, between your coils can be equal to the radius, RC, of...