lab3_em_electron

lab3_em_electron - PHY 252 Lab 3 e/m for electrons Fall...

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PHY 252 Lab 3: e/m for electrons Fall 2009, writeup version 2 In this experiment you will measure e/m , the ratio of charge to mass of the electron. This is the experiment that J.J. Thomson did at the Cavendish Laboratory in Cambridge in 1897, for which he received the Nobel Prize in 1906. The setup (Fig. 1) consists of a visible beam cathode ray tube used to produce a beam of electrons of known energy. The tube contains an electron gun which emits, accelerates and focuses electrons. The electrons with charge q = e are accelerated over a voltage V , so that they acquire a kinetic energy of E k = e · V = (1 / 2) mv 2 in the classical limit. The tub also contains a trace amount of gas which fluoresces when struck by electrons, so that you can see the beam trajectory by eye. The tube is supported at the center of a pair of large Helmholtz coils producing a uniform magnetic field B perpendicular to the velocity of the electrons. Therefore the electrons will be deflected to trace a circular path with a radius determined by
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lab3_em_electron - PHY 252 Lab 3 e/m for electrons Fall...

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