# Laws

## Kirchhoff's laws

 - **Point law:** all the current that flows into a node must come out of the node
 - **Loop law:** the sum of the voltage across any closed loop is zero

## Thevenin's Theorem

Any **linear** circuit can be simplified with a single voltage source
and a resistance in series.

The Thevenin voltage is an ideal voltage source
equal to the open circuit voltage at the terminals.

The Thevenin resistance r is the resistance measured
at terminals AB with all voltage sources replaced by short circuits and all
current sources replaced by open circuits.

 - [tutorial](http://www.allaboutcircuits.com/textbook/direct-current/chpt-10/thevenins-theorem/)
 - [Thevenin's Theorem](http://hyperphysics.phy-astr.gsu.edu/hbase/electric/thevenin.html)