multiple power sources (DC circuits)

Discussion in 'General Electronics Chat' started by LukeDXB, May 26, 2008.

  1. LukeDXB

    Thread Starter New Member

    May 25, 2008
    Hi Everyone,

    I have a general question.

    I can calculate series and parallel circuits ok, with one power source, such as a battery but how do I work out resistance values when there are two power sources (in a DC circuit)?

    For example, two 9v batterys wired in series, with 1 X 5 ohm and 1 X 10 ohm resistor and a 12v lamp - all in series.


  2. nanovate

    Distinguished Member

    May 7, 2007
    add them together
  3. John Luciani

    Active Member

    Apr 3, 2007
    The general method would be to use superposition. You determine the effect due to each
    power source individually, by disabling all but one source, and add the effects.

    To disable a voltage source replace it with a short circuit. To disable a current source
    replace it with an open circuit.

    For two equal voltage sources in series disabling one source gives you a current V/R.
    Disabling the second source also gives you a current V/R. Adding the two currents
    together gives you 2V/R.

    (* jcl *)