Rather simple ? regarding gel electrophoresis

[Daniel Mytelka]

In article <3bg86c$8at at news.ycc.yale.edu>,
J.Chang <jhc at minerva.cis.yale.edu> wrote:

   just out of curiosity, i've always wondered why, when i set it for
   the same voltage, different power machines read different values
   for the mA.  when i set the machine at 100V, for example, one machine
   might read 70mA while another reads 90mA.  

   these machines are the same brand and model, so i don't think it could
   be because of different machine specifications.

   also, does this discrepancy in mA affect results (resolution, etc)?
   i mean, do some of these machines produce better results than others?


V=I*R 
If the same model machines measure different currents at the same
voltage (assuming you use the same gel and just switch the leads, so
there isn't any significant external resistance difference), then:
one isn't working properly. Either the dial is wrong or there's
something screwed up inside which is generating resistance inside
the power supply. Assuming you don't go too high, this won't affect
resolution, but it will change run time.

Dan Mytelka
mytelka at mendel.berkeley.edu