Physics307L F08:People/Muehlmeyer/Eoverm

Introduction
By analyzing the motion of a beam of electrons in a magnetic and electric field, Thomson found that there is a ratio independent of all other experiemental factors: the charge-to-mass ratio. This of course proved his hypothesis that there is a constituent in this beam that is common to all matter: the electron. In this lab, we will re-live Thomson's experiment (or atleast a version of it), by acaccelerating electrons into a strong magnetic field created by Helmholtz coils surrounding the vacuum bulb. The electrons, experiencing a magnetic field force, will rotate in a circle on a plane perpendicular to the field. By oberving the radius of this circle, and by knowing the magnitude of the fields, we will be able to determine the e/m ratio. We will do this numerous times for both constant V and changing V situations. Our hope is to approximate the accepted value of

$$\frac{e}{m}=1.7563 \cdot 10^{11} \frac{C}{kg} $$

Brief notes on our set up, extensive notes on our data (with photographs), and a theoretical introduction can be found below in my lab notebook:
 * Lab Notebook

We will approximate today's accepted value of the e/m ration by taking two sets of data. A set where both V and I are changing, and a set where only V changes. The averages for all the trials of these two experiments can be found below:

Changing V and I
$$\frac{e}{m}=4.51731 \pm .128121 \cdot 10^{12}\frac{C}{kg} $$

% Error from actual= 2,472%

Constant V
$$\frac{e}{m}=4.72128 \pm .48565645561 \cdot 10^{11}\frac{C}{kg} $$

% Error from actual = 168%

Average from both Experiments
$$\frac{e}{m}=2.49472 \pm .104605 \cdot 10^{12}\frac{C}{kg} $$

% Error from actual = 1,320%

Conclusion
My approximation is terribly far off from the exact value, which is most likely due to some outlying pieces of data from trying to measure the radius of the beam circles with a bad photo program.