Circuits

- 4/17/10

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

In Series

In Series

- 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 - Rtotal R1 R2 R3
- Vtotal IRtotal
- Ohms Law applies across each individual device
- V1 IR1 V2 IR2 V3 IR3
- Sum of the voltage drops across the individual

devices is equal to the total voltage supplied by

the source - Vtotal V1 V2 V3

In Parallel

In Parallel

- 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 - Itotal I1 I2 I3
- Ohms Law applies across each individual device
- V I1R1 V I2R2 V I3R3
- Overall resistance of the circuit is less than

the resistance of any one of the branches - 1/Rtotal 1/R1 1/R2 1/R3

Combining Resistors

- Series Rtotal R1 R2 R3
- Parallel 1/Rtotal 1/R1 1/R2 1/R3

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