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Parallel CircuitsParallel Circuits
This presentation is designed to give you a broad sense of parallel circuits
Learning Objectives- Upon Learning Objectives- Upon completion of this lesson…completion of this lesson…
Students will know what a parallel circuit looks like
Students will know the relationships of voltage, current and resistance in a parallel circuit
Students will know how to compute the missing variable given the other two in regards to a parallel circuit
DefinitionDefinition
A circuit with multiple paths from the source through the various resistors in the circuit
Parallel CircuitParallel Circuit
Parallel CircuitParallel Circuit
R=ResistanceR=Resistance
1/Rt = 1/R1 + 1/R2 + 1/R3Rt = R1 x R2 / R1 + R2Rt = R (value)/ number of resistorsThe reciprocal of the total resistance is the
sum of the reciprocals of the individual resistances
R=ResistanceR=Resistance
1/Rt = 1/R1 + 1/R2 + 1/R31/Rt = 1/8Ω + 1/12Ω + 1/24Ω 1/ Rt = .125Ω + .0833Ω + .04167Ω1/Rt = .25Ω Rt = 1/ .25ΩRt = 4 Ω
V=VoltageV=Voltage
Vt = V1 = V2 = V3V1 = 120VV2 = 120VV3 = 120VVoltage in a parallel circuit is constant
throughout the circuit
I=CurrentI=Current
It = I1 + I2 + I3I1 = V1 / RtIt = 120V / 4Ω It= 30 AmpsThe total current of a circuit is calculated
adding the total individual currentsThe total resistance is calculated using total
voltage and total resistance
I=CurrentI=Current
It = I1 + I2 + I3 I1 = V1 / R1
– 120V / 8Ω – I1 = 15 Amps
I2 = V2 / R2– 120V / 12Ω – I1 = 10 Amps
I3 = V3 / R3– 120V / 24Ω – I3 = 5 Amps
I=CurrentI=Current
It = I1 + I2 + I3I1 = 15 Amps I2 = 10 AmpsI3 = 5 AmpsIt = 15 Amps + 10 Amps + 5 AmpsIt = 30 Amps
Parallel Circuit RecapParallel Circuit Recap
Electricity takes separate paths through the resistors and back to the source
If a resistor is broken then that particular section of circuit will not work. The remaining paths will still function
Parallel Circuit RecapParallel Circuit Recap
1/Rt = 1/R1 + 1/R2 + 1/R3Rt = R1 x R2 / R1 + R2 (with only 2)Rt = R (value)/ number of resistors (when
all resistor values are the same)Vt = V1 = V2 = V3It = I1 + I2 + I3
Practice:Practice:Complete the table with a partnerComplete the table with a partner
Vt
100 V
V1 V2 V3
Rt R1
15 Ω
R2
10 Ω
R3
5 Ω
It I1 I2 I3
Practice:Practice:Complete the table with a partnerComplete the table with a partner
Vt
50 V
V1 V2
Rt R1
20 Ω
R2
10 Ω
It I1 I2
Practice:Practice:Complete the table with a partnerComplete the table with a partner
Vt V1 V2 V3
Rt R1
8 Ω
R2
8 Ω
R3
8 Ω
It
2.5 Amps
I1 I2 I3
Follow up activityFollow up activity
Be sure to check the discussion board for the follow up activity