Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Capacitor discharge lab

  1. Nov 6, 2011 #1
    Hi what type of calculation errors should i do for my data on the capacitance discharge experiment.

    I had a voltage of 1.5V ,and I know the resistance, so the aim was to obtain the value of the capacitor, using the time constant RC=t formula.

    I done 4 trials , with the same voltage, ( roughly) and resistance each time.

    Should i do standard deviation etc??

    Thank you
  2. jcsd
  3. Nov 6, 2011 #2
    Interesting question. I don't have a simple clear cut answer. I'm not sure there is one.

    To begin, I'd note the accuracy of your resistance...is it, say, a 5% or a 1% rating. Did
    you actually measure the resistance...what value(s) did you get, and what is the accuracy of your measuring device. If you used, say a volt-ohmmeter maybe you could get a more accurate reading via a wheatstone bridge. How does the resistance of your wires compare??
    You should pick a large enough R to use so that the resistance of your wires is insignificant.

    What's the meter accuracy for your voltage and time readings? How were those values determined? for example, did you observe the fall off of voltage and then check the time of zero voltage on a wrist watch...to within one second?? Or did you have, say, an automatic device which measures, say, milliseconds? If your measuring device accuracy is on the scale of your time constant, your readings will be very unreliable.

    One way to get a rough idea of maximum error is the add all the variances in such a way that they all produce,say, increased values of your time constant. That won't happen much
    is an actual experimental environment but nothing prevents it either.

    You can get a better standard deviation by taking more than just four readings.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook