# 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.