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DC motor. Calculate the current

  1. Feb 6, 2014 #1
    1. The problem statement, all variables and given/known data

    The coil of a DC motor has a resistance of 2.0 ohms. The motor is runned by a battery of 12 V and an internal resistance of 0.5 ohms.
    a) Calculate the current at the moment the motor is started
    b) Calculate the current when the motor is running at 600 RPM , when there is an induced counter EMF of 10 V in the coil.

    2. Relevant equations

    I = E / R

    3. The attempt at a solution

    a) is already solved I = 24 A

    help with b), please
  2. jcsd
  3. Feb 6, 2014 #2


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    If you know the voltage from the internals of the battery and the voltage over the coil, what does the internal resistance of the battery see ?
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