1. 4/17/10

2. Electric Circuits Circuit = Any path along which electrons can flow For a continuous flow of electrons, there must be a complete circuit with no gaps A gap is usually provided by an electric switch that can be opened or closed to either cut off or allow electron flow

3. In Series

4. Current passing through each electric device is the same I1 = I2 = I3 Total resistance to current in the circuit is the sum of the individual resistances along the circuit path R total = R1 + R2 + R3 V total = I*R total Ohm’s Law applies across each individual device V1 = I*R1V2 = I*R2V3 = I*R3 Sum of the voltage drops across the individual devices is equal to the total voltage supplied by the source V total = V1 + V2 + V3

5. In Parallel

6. Voltage is the same across each device V1 = V2 = V3 Total current in the circuit equals the sum of the currents in its parallel branches I total = I1 + I2 + I3 Ohm’s Law applies across each individual device V = I1*R1V = I2*R2V = I3*R3 Overall resistance of the circuit is less than the resistance of any one of the branches 1/R total = 1/R1 + 1/R2 + 1/R3

7. Combining Resistors SeriesR total = R1 + R2 + R3 Parallel1/R total = 1/R1 + 1/R2 + 1/R3