User:Emran M. Qassem/e/m Ratio

LAB NOTEBOOK Here

Overview
In this lab we measured the ratio of e/m for electrons using an electric field on a charged particle. Knowing the electric field, measuring voltage, current, and the radius of curvature of the generated electron loop, we can calculate the e/m ratio.

The accepted value is $$ 1.76 * 10 ^{-11} \frac{coul}{kg}$$ as gathered from the lab manual. (Steve Koch 01:14, 13 October 2010 (EDT):Typo in your accepted value, should be +11)

Procedure
After setting everything up correctly according to the lab manual, we set voltages and currents, took measurements and logged them in the spreadsheet. Our first set of measurements, we didn't understand what was needed so we took two sets of current measurements for 5 different voltage measurements. Once we discovered that we needed to take 10 measurements, 5 currents at a constant voltage, then 5 voltages at a constant current, we did that and created some spreadsheets with that data. Once we had the data, we used the LINEST spreadsheet function to give us a fitted line based on a slope and intersection, and from that we generated data points and built a graph based on them.

Results
Using the results from the best fit line graphs, and using the equations given to us in the lab manual, we calculated e/m and found it to be $$ 1.83 * 10^11 \pm 8.5 * 10^9 \frac{C}{kg}$$ based on the error from our best fit line. I was quite satisfied with these results.

Error
The calculated result is off by 1 sigma from the accepted value, which is at about 68 percent accuracy. Error can be caused by our data collection as we could not get the exact measurement of the electron particle radius of curvature as the bulb had distortion and was very difficult to measure because of the low intensity of the particle beam which reduced visibility. Systemic error can be caused by the equipment.

Conclusion
Although our results were fairly reasonable, our data collection was all over the place at first, as we were not clear on what we needed to do. We learne how to use the spreadsheet and how to make graphs with best fit lines, which also very useful for this and future experiments.