DC Circuits

The main thing to know in the analyses of circuits, where some unknown parameters have to be calculated is to apply the Ohm's Law or Kirchhoff's Law. 

• Ohm's law says that the voltage drop across a resistance in a circuit is V = IR. 

• Kirchhoff's Law says that the total current flowing into a node is equal to the total current flowing out of the node. It also says that in a closed path in a circuit, the total voltage drop is equal to the sum of voltage rises. 

This page (accessed 10/6/15) provides some details on the Ohm's law, and here (accessed 10/6/15) are some details on Kirchhoff's law. Now for doing the calculations, there are several rules and special cases to know about: 

• Simple resistive circuit: Find the equivalent resistance, and voltage, and then using Ohm's law with equal current through all resistors, find the voltage drop for each resistor. This page (accessed 10/6/15) has much explanation and examples. Also this file I found from Youngstown State University has some illustrations.