1. 9.1 Series and Parallel Circuits
Pg. 306
People here have multiple paths to follow
An electric circuit is like a simple waterslide. A circuit that has only one path for current to travel is called a series circuit. In other words, electrons only have on path to follow. If the switch is opened, all electrons are blocked and the current stops.

2. Voltage decreases as electrons pass through each load
Series Circuits
Voltage decreases as electrons pass through each load
Voltages across each of the loads adds up to the voltage supplied by the source.
There’s only one path to follow
Current is constant throughout the circuit
Resistance of resistors increases when in series
- like more speed bumps in a row

3. Voltage is the same across each load
Parallel Circuits
Voltage is the same across each load
There’s more than one path to follow
Current varies between each pathway, depending on the resistance of the path, but still adds to the total current supplied by the source.
Resistance decreases with each added resistor
New pathway created thus lowering the total resistance
Junction point is where a circuit divides into multiple paths
The total current entering
a junction point must equal
the sum of the current leaving
the junction point

4. Use Christmas lights and room lights as examples

5. Find the unknown Voltage (V) and the Current (A) in each of the following circuit diagrams.
Voltage = 10.0 V Current = 3.0 A
Voltage = 12.0 V Current = 4.0 A

6. COMPARING SERIES & PARALLEL CIRCUITS
# of paths electricity can follow
One
More than one
Current throughout the circuit
Equal
Lower between
junction points
Voltage of loads in the circuit
Can vary
All the same
Effect of adding a second resistor on total resistance
Increases
Decreases
Effect of adding a second resistor on current

7. DRAWING PARALLEL & SERIES CIRCUITS
Draw a circuit diagram consisting of a 9.0 V battery, an ammeter, and a 25  resistor in series. Include a voltmeter that is measuring the potential difference across the resistor.
Draw a circuit diagram consisting of a battery made up of two 1.5 V cells, one closed switch, two lamps, and an ammeter in series. Show the direction in which the current flows.
Draw a circuit diagram consisting of a battery made up of four 1.5 V cells, one closed switch, one lamp, two 0.50  resistors in series, and a voltmeter. Show the direction in which the current flows.

8. MORE PRACTICE DRAWING PARALLEL & SERIES CIRCUITS
Draw a series circuit consisting of:
12 V electrical source
open switch
two light bulbs
10  resistor
Draw a parallel circuit consisting of:
9.0 V electrical source
three 5.0  resistors
Draw a circuit consisting of:
three 1.5 V cells connected in parallel
two light bulbs connected in series
two 15  resistors connected in parallel

9. INTERPRETING CIRCUIT DIAGRAMS
Describe what will happen in the circuit shown above if…
(a) the switch is closed
the switch is closed and the first bulb is removed
the switch is closed and the fifth bulb is removed
a) Current flows through whole circuit.
b) Current flow stops at the second bulb because circuit is interrupted.
c) Current flows through rest of circuit, bypassing fifth bulb.

10. Calculate the missing quantities for the circuit below.
A30. V1 = 7.5 V
R1 = 5.0 
R2 = 3.0 
A31. V1 = 40 V
R1 = 2.0 
V2 = 40 V