Data about our Helmholtz Coil pair:

  1. Diameter = 1.016 \pm 0.008 m
  2. R_{\mathrm{coils}} = 0.939 \pm 0.001\;\Omega
  3. R_{\mathrm{coils\, in\, parallel\, with \,leads}} = 0.516 \pm 0.001\;\Omega
  4. R_{\mathrm{coils\, in\, series\, with\, leads}} = 2.067 \pm 0.001\;\Omega
  5. diameter of coil wire = 0.075 \pm 0.001 in = 1.905\pm 0.025 mm
  6. Predicted number of turns = 49.9\pm 1.4 turns

These (home made) coils which I’ve inherited are clearly  marked as having 43 turns, so I’ve got quite a discrepancy here. I’m inclined to believe my measurements, but will have to check by putting a known current and measuring the magnetic field. A good project for a student measurement.

I’m adding a sensing resistor (1.420 \pm 0.001\; \Omega ) to the above in order to measure the current using the LabJack A/D. This resistance value includes the lead wires to the LabJack.

Addendum: (12 April 2012): I think that I have overestimated the resistance; will have to re-do measurements! Think this is not supposed to happen in a laboratory notebook? Unfortunately, it happens all the time, but hopefully we catch our mistakes.


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