Three Essential Laws for Working with Circuits - dummies

Three Essential Laws for Working with Circuits

By John Santiago

Part of Circuit Analysis For Dummies Cheat Sheet

At the most basic level, analyzing circuits involves calculating the current and voltage for a particular device. That’s where device and connection equations come in. Device equations describe the relationship between voltage and current for a specific device. One of the most important device equations is Ohm’s law, which relates current (I) and voltage (V) using resistance (R), where R is a constant: V = IR or I = V/R or R = V/I.

The two connection equations you need to know are Kirchhoff’s current law (KCL) and Kirchhoff’s voltage law (KVL):

  • Kirchhoff’s current law: Sum of incoming currents = Sum of outgoing currents at a node

  • Kirchhoff’s voltage law: Sum of voltage rises = Sum of voltage drops around a closed loop