e-over-m

e-over-m - by your TA • The principle by which an...

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PHY124 ELECTRON e/m Exp. 5 Abstract This lab is one of the favorite labs of most physics students since it provides the beautiful sight of a beam of electrons traveling in a circular path in a magnetic Feld. Since we can easily measure the electron’s energy (by the accelerating voltage) and calculate the magnetic Feld of the Helmholtz coils, we are able to determine the electron’s “charge-to-mass” ratio, e m . One unusual aspect of this lab is that the apparatus for making the measurement is self-contained. As such, we will use the instruction manual for that apparatus as our “lab manual”. 1 Knowledge, Understanding, and Skills You should have a “hands-on” experience and ability with all the following: How to derive from scratch the relation eB = mv r . You will likely be asked to perform this derivation by your TA. How to derive from scratch the relation e m = 2 V r 2 B 2 . You will likely be asked to perform this derivation

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Unformatted text preview: by your TA. • The principle by which an energetic beam of electrons is generated using Flaments and voltages. • Why the path of the beam is visible to the human eye (it would not be visible traveling through vacuum). • You should be able to use your knowledge of the electron’s charge to determine for your apparatus: – The direction of the magnetic Feld in your apparatus that causes the electron to move in a circular path. – The direction of the current in the coils required to make this magnetic Feld. 2 Equipment • 1 EP-20 e/m Apparatus. • 1 EP-20 Instruction Manual. PHY124 ELECTRON e/m Exp. 5 3 Procedure 1. Follow the instructions found in the EP-20 manual, measuring e m for 8 di±erent combinations of accelerating voltage V , path radius r , and coil current I . 2. After you have produced a correct value for e m , call your lab TA over for an interview....
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This note was uploaded on 11/26/2009 for the course PHY 124 taught by Professor Staff during the Fall '08 term at SUNY Stony Brook.

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e-over-m - by your TA • The principle by which an...

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