1. Circuits
Series
Parallel

2. V = IR Ohm’s Law V = Voltage (Volts) I = Current (Amps)
R = Resistance (Ohms)

3. Series Circuits
Have only one path
The battery is represented by the escalator which raises the charges to a higher energy level (voltage source).
As the charges move through the resistors (represented by the paddle wheels) the charges do work (J/C), and subsequently, lose energy (experience a voltage drop).
The charges do more work as they pass through the larger resistor.

4. By the time each charge makes it back to the battery, it has lost all of the energy given to it by the battery.
The sum of the potential drops (voltage drops) is equal to the potential rise (voltage source) from the battery.
This demonstrates that a charge can only do as much work as was done on it by the battery.

5. Series Circuits Vtot = V1 + V2 +… Itot = I1 = I2 = …
The sum of the potential drops equals the potential rise of the energy source
The current is the same throughout the circuit
The total resistance of the circuit (equivalent resistance) is equal to the sum of the individual resistances.
Vtot = V1 + V2 +…
Itot = I1 = I2 = …
Rtot = R1 + R2 + …

6. Symbols Used in Drawing Circuits

7. R1 = 2 ohms R2 = 3 ohms R3 = 1 ohm VB = 12 V (voltage source)
Find the equivalent resistance of the circuit.
Find the current of the circuit
Find the voltage drop at each resistor

8. Draw a circuit that has:
12 volt battery source
3 Ω resistor
2 Ω resistor
Calculate the equivalent resistance in the circuit
Calculate the current in the circuit
Calculate the voltage drop across each resistor

9. Parallel Circuits

10. Voltage
The potential drops of each branch equal the potential rise of the source.
The voltage is the same through each resistor

11. Current
The total current is equal to the sum of the currents in the branches
The current can branch into new pathways that can allow different currents per path.

12. Resistance
The total resistance of the parallel circuit is equal to the inverse of the sum of all the inverse resistance combined
Straw comparison!!

13. Parallel Circuits
If your voltage source = 12 V, what is the voltage across each resistor (assume they have the same resistance)?
What is the voltage across each resistor if all three resistors are different?

14. Current in Parallel Circuits
Current is divided in the branches
Resistance of individual resistors determines how much current will flow through it
So – essentially, the currents will be different through each of the resistors.

15. Current in Parallel Circuits
1) Find the equivalent resistance of the circuit
2) Find the total current flowing in the circuit
3) Find the current flowing through each resistor
VB = 12 V R1 = 3 Ω
R2 = 2 Ω R3 = 1 Ω