1. Series and Parallel Circuits
Chapter 23 Notes
Series and Parallel Circuits

2. Section 23.1 Objectives
Differentiate between series and parallel circuits.
Calculate currents, voltage drops, and equivalent resistances in series and parallel circuits.

3. Electric circuits
Open circuit
Closed circuit
Short circuit

4. Series Circuits Equivalent resistance Current Voltage drops
R = RA + RB + …
Current
I = Vsource/R
Voltage drops

5. Example Problem
Two resistors, 47.0 Ω and 82.0 Ω, are connected in series across a 45.0 V battery.
What is the current in the circuit?
What is the voltage drop across each resistor?
If the 47.0 Ω resistor is replaced by a 39.0 Ω resistor, will the current increase, decrease, or remain the same?
What is the new voltage drop across the 82.0 Ω resistor?

6. Parallel Circuits Equivalent resistance Current Voltage Ohm’s law
1/R = 1/RA + 1/RB + 1/RC + …
Current
Ohm’s law
Voltage

7. Example Problem
Three resistors, 60.0 Ω, 30.0 Ω, and 20.0 Ω, are connected in parallel across a 90.0 V battery.
Find the current through each branch of the circuit.
Find the equivalent resistance of the circuit.
Find the current through the battery.

8. Section 23.2 Objectives
Describe devices used to protect household wiring.
Solve problems involving combined series and parallel circuits.

9. Safety Devices
Short circuit
Fuse
Circuit breaker

10. Combined Series-Parallel Circuits

11. Problem-Solving Strategies

12. Example Problem
A hair dryer with a resistance of 12.0 Ω and a lamp with a resistance of 125 Ω are connected in parallel to a 125 V source through a 1.5 Ω resistor in series. Find the current through the lamp when the hair dryer is on.