2. Circuits
In order for electricity to flow we need
Power source
Closed circuit
There are two type of circuits we will
explore
Series circuit
Parallel circuit
3. Series Circuit
In a series circuit there is only one path for
the electrons to flow
In other words all the components are in
series with each other
Because there is only one path each
charge will go through each resistor
4. Predict, Test and Explain
• How will the brightness of the bulbs change
as we add more in series?
• What does this imply about the current in the
circuit?
+
+ +
5. Parallel Circuit
In a Parallel circuit there are multiple pathways for
charge to flow
Each device is placed on it’s own separate branch
Current goes through each of the branches at the same
time
6. • How will the brightness of the bulbs change
as we add more in parallel?
• What does this imply about the current in the
circuit?
Predict, Test and Explain
+ + +
7. Key Concepts
Bulbs in series represent a source of
resistance to current flow, similar to
boulders in a stream which can block
the flow of water
Bulbs in parallel offer additional
pathways for current flow, similar to
branches of a stream which can carry
more water.
8. Calculating Resistance in Series
Circuits
The rule for
calculating Series
Circuits is to…
Add up the values of
each individual in the
series.
R1 + R2 + R3…
5 + 5 + 10
20 Ω (ohms)
9. Calculating Resistance in Series
Circuits
Add up the values of
each individual in the
series.
R1 + R2 + R3…
10 + 20 + 10
40 Ω (ohms)
10
20
10. Calculating Resistance in Series
Circuits
The rule for calculating Series
Circuits is to…
Add up the values of each
individual in the series.
1 1 1 1
-- = -- + -- + --
Rt R1 R2 R3
1 1 1 1
-- = -- + -- + --
Rt 4 4 2
1
-- = .25 + .25 + .5
Rt
1
-- = 1
Rt
1
-- = 1
Rt
20
1
-- = 1
Rt
1
-- = Rt
1
Rt = 1 Ω (ohms)
11. Calculating Resistance in Series
Circuits
• The rule for calculating Series
Circuits is to…
• Add up the values of each
individual in the series.
• 1 1 1 1
-- = -- + -- + --
Rt R1 R2 R3
• 1 1 1 1
-- = -- + -- + --
Rt 100 200 1000
• 1
-- = .01 + .005 + .001
Rt
• 1
-- = .016
Rt
• 1
-- = .016
Rt
20
• 1
-- = Rt
.016
• Rt = 62.5 Ω
(ohms)
100 200 1000
