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Kirchoff's Laws

The conservation of energy and conservation of charge when applied to electrical circuits are known as Kirchoff's laws.

Conservation of energy - zero algebraic sum of the voltage drops around a closed circuit loop (imaginary loop)

Conservation of charge - zero algebraic sum of the currents flowing into a point (total charge in, equals total charge out)

When applying these laws to solve for circuit unknowns we will find the following definitions useful:

Using these definitions we can apply Kirchoff's laws to a circuit to solve for the unknown quantities. The general procedure is:

  1. define the currents and voltages on a diagram,
  2. apply Kirchoff's laws to loops and nodes,
  3. write down a set of linear algebraic equations, and
  4. solve for the unknowns.

But before we look at general circuits lets consider how simple resistors add.

Doug Gingrich
Tue Jul 13 16:55:15 EDT 1999