Northwestern Physics Demos                                 Go back to MAGNETISM 
DCS# 5H30.15NWU#  E-37Location:    9D-1
title: Electron Deflection
aka: Magnetic difflection of cathode rays

A cathode ray tube is excited by a small tesla  coil mounted on a ring stand.  The cathode rays are narrowed to a beam by a slit and run along a fluorescent screen.  A magnet can deflect the beam by directing the field horizontally and perpendicular to the beam.

Warning:  soft x-rays are emitted from this device.   Keep the excitation voltage as low as possible to keep the x-rays soft.

   How would you position a horse-shoe magnet to maximize the deflection?
   How would you hold a bar magnet to maximize the deflection?

pix of set upcathode ray beam undeflectedbent beam