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Showing posts from November, 2014

### EM II Notes 2014_11_24: Leinard-Wiechert Potentials

There's sooo much going on today.  I'm back in the lab again, but I'm also studying for the last little bit of my EM II class.   Here are the EM notes for today.  Hopefully, I'll get a lab book up again in the morning.

Looking at the Leinard-Wiechert Potentials.

### YBCO Four Point Measurements: Lab Book 2014_11_15

I was back in the lab this morning.  I’m working on getting the four point measurement to work on the YBCO sample.  In the grand scheme of things, this is low priority, but it’s important to know that we can successfully make these measurements here before we have a large bucket of liquid helium evaporating with a sample inside.  Here’s what the four point probe measurement looked like:

There are still no conclusive results.  With any luck this is a consequence of me not being able to interpret the results more than a bad experimental setup.  The table below details the four point probe readings in ohms as the superconductor cools
Table of four point readings Time Resistance kohm Comments 0 -0.35444 Negative reading is probably from swapped sense wires. 16 -0.36735 Immediately after nitrogen pour 59 -0.34466 Near minimum 101 -0.34359 Minimum immediately after new pour 280 -0.3