documentation:

• instruction manual.
• PSSC description of experiments
• Air core solenoid documentation
  (note that the field strength information is incorrect; you have to determine the magnetic field yourself (count the number of turns in the outermost layer; there are three identical layers))

    notes:

• the focus is on experiments 29 and 30 described in the PSCC document -- measurement of the electron mass and the Earths' magnetic field.
• modification for experiment 29:
  Instead of finding the magnet current for which the solenoid field causes a deflection at 90^o with respect to the deflection due to the voltage across the Y plates (see p 4 to 5 of the PSSC document), follow the procedure described below:
  1. For a given accelerating voltage V_a, determine the coordinates of the electron impact point A for V_Y = 0 and solenoid current I_S = 0.
  2. Determine the coordinates of the electron impact point B with the Y plates connected to the power supply, and I_S = 0.
  3. With the Y plates connected to the power supply, increase the current I_S in the solenoid in small steps; watch the impact point C of the electron move; record the coordinates of the impact point for at least five different values of I_S. Note when the impact point has made a full circle (spiral) around point A (you'll have to account for this in the angle α to be determined from the coordinates of the points A, B, C.)
  4. Determine the angle α between the lines AB and AC (note that you may have to add appropriate multiples of 360^o (or 2π)).
  5. Repeat steps (1) to (4) for at least five values of V_a between 200 and 350 V.
  6. Find a relation betwen the angle α defined above and the angle φ by which the electron has travelled along a circular path in the plane transverse to the axis of the solenoid (simple geometry -- properties of triangle and circle).
  7. generalize equation (3) of the PSSC document for an arbitrary angle φ (equ. (3) was derived for φ = 180^o).
  8. Repeating (and generalizing) the reasoning in the derivation of equation (4) of the PSSC document, derive a relationship between α (or φ), V_a, B (solenoid field), D (distance from Y plates to tube face), and e and m of the electron.
  9. Find a way to plot your data so that a straight line can be fitted, with the slope providing information about the mass of the electron. (You should give the mass of the electron in MeV/c²).
  10. calculate the uncertainty of the slope and from it determine the statistical uncertainty of the electron mass. Are there any systematic errors that you have to consider? Discuss this in your report.

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