1. Series and Parallel Circuits

2. Equivalent Resistance
The equivalent resistance of a circuit is the amount of resistance which a single resistor would need in order to equal the overall effect of the collection of resistors which are present in the circuit.

3. Series Circuits
In a series circuit there is a single pathway for electrons to flow through.
The current passing through each electrical device in the circuit is the same.
The total resistance to current in the circuit is the sum of the individual resistances along the path.
The current in the circuit is equal to the voltage supplied by the source divided by the total resistance of the circuit (Ohm’s Law).
Ohm’s law also applies separately to each device.
The sum of the voltage drops across each device is equal to the total voltage supplied by the source.

4. Series Circuits
How is the ammeter wired? Series or parallel?
Ammeter (measuring current)
resistor
What one resistor could replace these 3 resistors and allow the same current to flow through the circuit?

5. Series Circuits
Req = R1 + R2 + R

6. Series Circuits

7. Ohm’s Law V = I R
Applies to the circuit as a whole, but also to any small part of the circuit (like a single resistor).

8. Series Circuits

9. Series Circuits
Ohm’s Law applies to the circuit as a whole, but also applies to this one resistor.
What values do you know inside this circle?
Voltmeter
(measuring volts)
How is the voltmeter wired? Series or parallel?

10. Series Circuits

11. Series Circuits 3V

13. Parallel Circuits
In a parallel circuit current can flow through more than one pathway.
The voltage is the same across each device.
The amount of current in each branch is inversely proportional to the resistance of the branch. (Ohm’s law applies to each branch).
The total current equals the sum of the currents in the parallel branches.
As the number of parallel branches is increased, the overall resistance of the circuit is decreased.

14. Parallel Circuits
What one resistor could replace these 3 resistors and allow the same current to flow through the circuit?

15. Parallel Circuits

16. Parallel Circuits

17. Parallel Circuits

18. Equivalent Resistance in Complex Circuits

19. Ohm’s Law in Complex Circuits
Consider this circuit with three resistors. Add some meters….