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Homework Help: Electric Circuit and Internal Resistance Lab

  1. Feb 23, 2009 #1
    1. The problem statement, all variables and given/known data
    I performed a lab where we designed an electric circuit on paper and then calculated the Current, Power, and Voltage for each of the resistors. We used one power supply. Then we built the circuit we designed and then measured the actual Current Power and Voltage for the it using a multimeter. However, all the values for the actual measurements are just slightly lower than the numbers of the predicted values. I think it has to do with the internal resistance of the battery, but i am not sure. Would i calculate it using V=IR and use the actual total voltage and total current?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 23, 2009 #2


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    Homework Helper

    Yes, use the actual values in your calculation. A good idea to have thought of internal resistance - and to calculate it.

    You might also want to mention imperfect meters. Current meters have to be inserted in the circuit and they add resistance to it. Voltmeters have less than infinite resistance and draw some extra current.

    Meters can be out of whack, too. Not a bad idea to check your meter against another one in the lab or some reference voltage such as a disposable AA battery.
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