1. Kirchoff and the Circuit October 20, 2012

2. Rules for Review Parallel 1/R T = 1/R 1 + 1/R 2 +... I T = I 1 + I 2 +... V 1 = V 2 =... Series V T = V 1 + V 2 +... I T = I 1 = I 2 =... R T = R 1 + R 2 +...

3. And What About Energy? Capacitors Store It U = 1/2 QV Resistors Use It P = IV where P is Power (watts) P = I 2 R = V 2 /R

4. Practice Lets find some current and potential differences and power values

5. So What if the Circuits are Ridiculous? Thanks be to Kirchoff. Two Rules to solve ANY circuit. Rule 1: Junction Rule: Current flowing into any junction = current flowing out Rule 2: Loop Rule: Sum of the potential differences around any complete loop = 0

6. Sample Problem Find the current When is V positive and when is it negative Depends on direction of the current and of the loop Loop Sign Rules

7. Sample Problem Find each current Find the voltage across each resistor.