Physics307L F08:People/Gooden/Eoverm

From OpenWetWare
Jump to: navigation, search
  • This lab was the measure of the e/m (charge-to-mass ratio) ratio of the electron.
  • A complete list of materials and procedure can be found here in my lab write up

E/M or in the previous course lab manual Previous Course

  • The collection of data is difficult to make on the apparatus.There is a reflective/mirrored ruler behind the tube which you are suppose to use to measure the radius of the circle formed by the electrons flowing inside. Lining up the circle onto the ruler can be difficult and eye straining.


We took three sets of data which each contained ten measurements. For each set we found a value for the charge-to-mass ratio, which are :

  e/m = 6.28343E+11 +/- .725E+11
  e/m = 3.39E+11 +/- .0272E+11
  e/m = 3.07111E+11 +/- .00840E+11

Accepted Value of E/M

  e/m= 1.758 820 150(44)e+11 C/Kg

  • So as you can see we have a large discrepency between our experimental value and the accepted value. Me and my lab partner Zane Gibson, believe this is due to errors inherent in the apparatus itself, since another group obtained very similar data.
  • The circle formed in the tube by the electrons is not perfectly circular and by looking at it you can see that the radius becomes less and less as you go around the circle. Also, there could be a problem in whether the circle is really centered on the zero mark of the ruler.
  • Needless to say we are not very happy with our results


SJK 00:29, 18 October 2007 (CDT)
00:29, 18 October 2007 (CDT)
Good ideas...and I think we also had some other ones...
  • If we were given enough time we believe we could possibly discover how to more accurately perform the experiment. We believe making sure the circle is centered on the ruler, would help. Also, trying to find a way to make the circle more uniform, possibly playing with focus on the apparatus could help in that regard, which would reduce error in measuring the radius.