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Unit 4- Building from
Schematics--Continued
EET 110 Electronics Survey I
Topics to Cover



Ohm’s Law as applied to Parallel
Circuits
Review Types of representations
Wiring from schematics
Ohm’s Law Relationships
Voltage (E) Amperes (I) Resistance (R)
E
E= I X R
I= E/R
R= E/I
I
R
Relationships in Parallel
Circuits
Parallel Circuit has multiple paths for
electron flow through devices wired in
the circuit
ET= E1=E2=E3=EN
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RT= R1+R2+R3+RN
IT= I1+I2+I3+IN
Parallel Voltage in a
circuit
The voltage in a parallel circuit is
equal to the source voltage.
ET= E1=E2=E3=EN
E = 12v
ET= 12v=12v=12v
ET= 12v
E = 12v

1
2
E3= 12v
ET= 12v
Kirchhoff’s Current Law
The algebraic sum of all currents
entering any point will equal the sum
of all currents leaving that point.
IT= I1+I2+I3+IN

I1= 2A
I2= 4A
I3= 3A
IT= 9A
Parallel Resistance in a
Circuit

When resistors are connected in a parallel circuit,
the total resistance of the parallel circuit is always
less than the smallest resistance.
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RT= R1+R2+R3+RN
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1
1
RT= 2Ω + 3Ω + 6Ω
R1= 2Ω
R1= 3Ω
1
6
4
2
RT= 12Ω + 12Ω + 12Ω
R1= 6Ω
1
12
RT= 12Ω= 1Ω
R1= 1Ω
Solving for Unknown
Values in a Parallel Circuit


At each resistor and the total resistors
Ohm’s law should hold true.
The Series Circuit Principles will hold
true.
E=I x R
ET= E1=E2=E3=EN
1
1 1 1 1
RT= R1+R2+R3+RN
IT= I1+I2+I3+IN
Practice Solving the
Circuit
Pictorial Drawing of Two
Receptacles
Schematic Drawing of 2
receptacles
Schematic Drawing of a
switched receptacle
Lab 7 wiring from
Schematics


2 switches controlling a light
3 switches controlling a light
Representations (cont.)

Schematics
– Clearly show
Types of devices and conductors
 Where they should be located
 Electrical Connections

– Typically for controls or equipment
– Provided by engineer, manufacturer
2 switches controlling a
light
Schematic
12 3/g
Source
12 2/g
3 switches controlling a
light
Schematic
Source