Kirchoff's Laws
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German physicist Gustav Robert Kirchhoff, developed two laws for electrical circuits, they are known as Kirchhoff's Laws of Networks.
- The first of Kirchhoff's laws states that at any junction in a circuit through which a steady current is flowing, the sum of the currents flowing to the point is equal to the sum of the currents flowing away from that point. In automotive terms, the current leaving the automobile positive battery terminal is equal to the current entering the negative battery terminal. In the circuit below, 2A of current leave the 12V source and 2A comes back into the 12V source ground.
- The second law states that, starting at any point in a network and following any closed path back to the starting point, the net sum of the electromotive forces encountered will be equal to the net sum of the products of the resistances encountered and the currents flowing through them. In automotive terms, this means that all of the battery voltage is dropped (or used up), in every single circuit on the automobile, between the positive battery terminal and the battery negative terminal. In the circuit below, there are two separate paths to ground for the current to take; each path has the entire 12V dropped across it. The first path drops 6V across the series resistor and another 6V dropped across the first branch of the parallel circuit. The second path drops 6V across the series resistor and another 6V dropped across the second branch of the parallel circuit. In both instances, all 12V was dropped between the voltage source and ground. See more examples below.
Copyright 2008,
by the Contributing Authors.
Cite/attribute Resource.
jfrank. (2008, February 12). Kirchoff\'s Laws. Retrieved November 22, 2009, from WSU Web site: http://ocw.weber.edu/automotive-technology/ausv-1320-automotive-electronics/3-basic-circuit-theory/kirchoffs-laws.
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