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Series
• Page 354
• Components are connected one after another
• There is only one pathway for electrons to
travel
• The current is the same at all the points in the
circuit
ITotal = I1 = I2
Series
We can use Ohm’s law to calculate:
Total voltage (potential difference) – Vtotal
Total Resistance – Rtotal
Total Current – Itotal
Vtotal = Itotal x Rtotal where
Vtotal = V1 + V2 + V3 (If there were 3 batteries)
Rtotal = R1 + R2 + R3 (If there were 3 resistors)
Itotal = Is the same throughout a series circuit
Series
• Series circuits are used when there is a need for
a lot of power to operate an electric device.
• An example would be a portable stereo which
contains a number of batteries in series.
Parallel
• Page 355
• Components are arranged in separate
branches
• There are multiple pathways for the
electrons to travel
• The current is not the same at all the points
in the circuit but initial current and final
current must equal.
Parallel
Again we can use Ohm’s law to calculate:
Total voltage (potential difference) – Vtotal
Total Resistance – Rtotal
Total Current – Itotal
Vtotal = Itotal x Rtotal where
Vtotal = Is the same across the circuit
Itotal = I1 + I2 + I3 (the sum of the currents through each branch of
the circuit)
1
1
1
1
Rtotal = R1 + R2 + R3 (If there were 3 resistors)
The equivalent resistance is always smaller than the smallest
resistance. (p.367)
Parallel
Parallel circuits are used in electrical devices that
we want to last a long time.
Remote controls and programmable calculators
use batteries connected in parallel
Series and Parallel Examples
If we had three resistors of 3Ω, 4Ω, and
8Ω in a series circuit.
Equivalent resistance in a series circuit
is larger than any individual resistor
Requivalent = R1 + R2 + R3
Requivalent = 3Ω + 4Ω + 8Ω = 15Ω
Series and Parallel Examples
If we had three resistors of 12Ω, 12Ω,
and 12Ω in a parallel circuit.
The equivalent resistance is always
smaller than the smallest resistance.
1/Requivalent = 1/R1 + 1/R2 + 1/R3
1/Requivalent = 1/12Ω + 1/12Ω + 1/12Ω
1/Requivalent = 3/12Ω
Series and Parallel Examples
1/Requivalent = 3/12Ω
1/Requivalent = 1/4Ω
If we multiply both sides of the
equation by 4Ω x Requivalent we get
Requivalent = 4Ω
The resistance of the three resistors in
parallel is 4Ω
Circuit Diagram Symbols