11/27/2023
24
FOURAH BAY COLLEGE
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
APPLIED ELECTRICITY I (EENG212)
LECTURE NOTES
PARALLEL DC NETWORKS
25
FOURAH BAY COLLEGE
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
APPLIED ELECTRICITY I (EENG212)
LECTURE NOTES
Lesson 2.3. (Parallel Circuit)
I2
I
I
I1
R1
V
I = I1 + I2
=
+
R2
V
RT
V
=V
1
1
1
= +
𝑅𝑇 R1 R2
+
𝑅𝑇 =
1
11/27/2023
26
FOURAH BAY COLLEGE
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
APPLIED ELECTRICITY I (EENG212)
LECTURE NOTES
Example 1. Calculate the current I, I1 and I2.
I
𝑅𝑇 =
I2
NODE
I1
12v
15Ω
𝑅𝑇 =
,
𝑅𝑇 =
10 Ω
I=
NODE
 For parallel circuits, the current flowing towards a
Junction is divided into branches
 Kirchhoff Current Law (KCL) states that “The algebraic
sum of the currents flowing to a node is zero”
 Current flowing towards the junction are positive
 Current flowing away from the junction are negative
I – I1 – I2 = 0
𝑽
, 𝑰=
𝑹𝑻
I1 =
I2 =
𝑽
𝑹𝟏
𝑽
𝑹𝟐
∗
𝑅𝑇 = 6 Ω ,
𝟏𝟐
𝟔
, 𝑰𝟏 =
, 𝑰𝟐 =
=𝟐𝑨
𝟏𝟐
𝟏𝟓
𝟏𝟐
𝟏𝟎
= 𝟎. 𝟖 𝑨
= 𝟏. 𝟐 𝑨
I1 + I2 = 0.8 + 1.2 = 2A
27
FOURAH BAY COLLEGE
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
APPLIED ELECTRICITY I (EENG212)
LECTURE NOTES
Example 2. Calculate effective resistance of the circuit.
R1
I
V
NODE 1
R1
R3
I
I2
I1
R2
R4
V
NODE 1
I1
R2
I2
R5
NODE 0
NODE 0
Note: R3 and R4 are in series
R3 + R4 = R5
(R5 // R2) =
RT = R1 +
2
11/27/2023
28
FOURAH BAY COLLEGE
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
APPLIED ELECTRICITY I (EENG212)
LECTURE NOTES
Example 3. Calculate the current I, I1 and I2.
14 Ω
I
12Ω
8Ω
NODE 1
I2
I1
7Ω
10 Ω
160V
I
160 v
NODE 1
14 Ω
I1
I2
18 Ω
10 Ω
NODE 0
NODE 0
RT = 14 + [10 // (8 + 7)]
I=
RT = 14 + 10 // 15
RT = 14 + 6 = 20 Ω
I=
I=8A
,
,
CLASSWORK
29
FOURAH BAY COLLEGE
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
APPLIED ELECTRICITY I (EENG212)
LECTURE NOTES
Example 2
Compute the current I in the figure below
I
8A
+
24V
--
16Ω
16Ω
16Ω
3
11/27/2023
30
FOURAH BAY COLLEGE
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
APPLIED ELECTRICITY I (EENG212)
LECTURE NOTES
Current Divider Rule
IT
IR1
R1
V
To find IR1
IR2
IT = V(
R2
V = IT /(
IT
= I1 + I2
)
+
V = IT /(
𝑉
V
V
=
+
𝑅𝑇
R1 R2
)
V = IT (
I1 =
)
+
)
= [IT (
IR1 = IT (
To find IR2
IR2 =
)](
)
= [IT (
IR2 = IT (
)
)](
)
)
31
FOURAH BAY COLLEGE
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
APPLIED ELECTRICITY I (EENG212)
LECTURE NOTES
Example 1
Calculate the current I, I1, I2 and I3 in the figure
below using the Current Divider Rule
I
24V
+
--
12Ω
I3
I2
I1
10Ω
18Ω
4