multiple power sources (DC circuits)

LukeDXB

Joined May 25, 2008
1
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.

Regards,

Luke

nanovate

Joined May 7, 2007
666

John Luciani

Joined Apr 3, 2007
477
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.

Regards,

Luke
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 *)