So far, we have considered circuits which can be reduced

1. 6 V So far, we have considered circuits which can be reduced to a single loop circuit and applied Ohm’s law to extract I and/or V in the circuit. 5 3

2. Georg Simon Ohm Gustav Robert Kirchoff LAW & ORDER

3. Statement of Kirchhoff’s Rules • Junction Rule • The sum of the currents entering any junction must equal the sum of the currents leaving that junction • A statement of Conservation of Charge • Loop Rule • The sum of the potential differences across all the elements around any closed circuit loop must be zero • A statement of Conservation of Energy

4. I2 I1 I3 = + Kirchoff’s Rules (1) Node rule, current law,.. I1 = I2 + I3

5. (2) Loop rule, V-law,.. D B C R1 V R2 E A F V A B C D E F A

6. IR1 IR2 R1 R2 IR3 R3 V I V V– IR1 – IR2 – IR3 = 0 V = I (R1 + R2 + R3) = I Req

7. I1 I I2 I3 R1 R2 R3 4 unknowns Need 4 independent eqs. V (1) I = I1 + I2 + I3 V/R1 = I1 (2) V – I1R1 = 0 (3) V – I2R2 = 0 V/R2 = I2 V (1/R1+1/R2+1/R3) = I (4) V – I3R3 = 0 V/R3 = I3 1/Req V = IReq