1. Parallel Circuits

2. Total Resistance in Parallel Circuits
Adding more resistors to a parallel circuit adds more paths for energy to flow.
With more paths, the total resistance drops as the number of resistors increases.
1/Rtotal = 1/R1 + 1/R2 + 1/R3…..

3. Sample Problem What is the total resistance in the circuit shown? 12V
15 B
20 C
17

4. Total Voltage in Parallel Circuits
The voltage across the resistors in parallel circuits are equal.
The voltage is equal to the voltage from the battery.

5. Sample Problem What is the voltage across resistor A?
What is the voltage across resistor B?
12V A
15 B
20 C
17

6. Total Current in Parallel Circuits
The current in the resistors of a parallel circuit depends on the resistance.
I = V/R
The total current is equal to the sum of the current from each resistor.
Itotal = I1 + I2 + I3 …

7. Sample Problem What is the current across C?
What is the total current?
12V A
15 B
20 C
17