Source transformation: Difference between revisions

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Revision as of 02:39, 21 October 2013

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== Process ==

Performing a source transformation consists of using [[OhmsOhm's Lawlaw]] to take an existing [[voltage source]] in [[series circuit|series]] with a [[resistor|resistance]], and replace it with a [[current source]] in [[parallel circuit|parallel]] with the same resistance. Remember that OhmsOhm's law states that a voltage in a material is equal to the material's resistance times the amount of current through it (V=IR). Since source transformations are bilateral, one can be derived from the other. <ref name="Nilsson">Nilsson, James W., & Riedel, Susan A. (2002). ''Introductory Circuits for Electrical and Computer Engineering''. New Jersey: Prentice Hall.</ref> Source transformations are not limited to resistive circuits however. They can be performed on a circuit involving [[capacitors]] and [[inductors]], as long as the circuit is first put into the [[frequency ___domain]]. In general, the concept of source transformation is an application of [[Thévenin's theorem]] to a [[current source]], or [[Norton's theorem]] to a [[voltage source]].

Specifically, source transformations are used to exploit the equivalence of a real current source and a real voltage source, such as a [[battery (electricity)|battery]]. Application of Thévenin's theorem and Norton's theorem gives the quantities associated with the equivalence. Specifically, suppose we have a real current source I, which is an ideal current source in [[Series and parallel circuits|parallel]] with an [[Electrical impedance|impedance]]. If the ideal current source is rated at I amperes, and the parallel resistor has an impedance Z, then applying a source transformation gives an equivalent real voltage source, which is ideal, and in [[Series and parallel circuits|series]] with the impedance. This new voltage source V, has a value equal to the ideal current source's value times the resistance contained in the real current source <math>V=I*Z</math>. The impedance component of the real voltage source retains its real current source value.