Slide 1

Kirchoff and the Circuit October 20, 2012 Slide 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 +... Slide 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 Slide 4 Practice Lets find some current and potential differences and power values Slide 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 Slide 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 Slide 7 Sample Problem Find each current Find the voltage across each resistor.