The CRT & Plum Pudding Model

By Erick MacCormack and Sami Cote


J.J. Thomson built a cathode ray tube with a metal cylinder on the end of it. The cylinder had two slits in it, leading to electrometers, which could measure small electric charges. Electrons are negative. The anode is positive, so it attracts the electrons pouring off the cathode.

A Subatomic Particle was Discovered

During the test, he noticed the light glow getting pulled toward the positively charged magnet. Thus, he decided that the electron gun was shooting negatively charged atoms called electrons.

The Plum Pudding Model

The Plum Pudding model was devised in 1897 by J.J Thompson as a result of his cathode ray tube experiment. It's an atom with a positively charged 'soup' as it's called, and it has freely floating electrons. It's accurate in that it has negative and positive charged objects, and right in that there are electrons, however, it's wrong in that the protons (the positively charged particle) are in a cluster in the center of the atom, and the electrons move rapidly around the exterior of the atom.