Exp 3: Charge to Mass (or E/M)

PHYS 47100 - Spring 2026

Due March 30

By measuring the trajectory of electrons in a magnetic field, one can obtain a ratio for the charge/mass of an electron.

Apparatus Manual: (pdf)

What the loop should look like:

We could do this experiment completely with an automated image capturing method. That is, use a camera to image the beam as we change variables and record the values of the voltage and current simultaneously. This would involve extracting a line profile of color data like the image shown here and then some peak finding/calibrations.

We'll still do this experiment by hand, with manual measurements, but, as a proof of concept, we'll analyze one image to include in the lab reports. The instructions are found in the Apparatus Manual pdf above.

To Submit:

  1. Table of Data that you took, in csv format, also accessible online.
  2. Short write up indicating what you did.
  3. Link to any code used.
  4. Explanation of the how you extracted the $e/m$ ratio from your data.
  5. Error reporting in your measurements and confirmation that your results are within the expected error.
  6. An image you took of the experiment and a line extraction plot that shows the beam in a line profile, as shown above.

Other Notes

This is probably the easiest of the experiments all semester. It will probably take less than the whole two hours (but it might.)