Series ----------------- Basic Knowledge

Electrical Fundamentals
ELE 801

A.Y : 2024-2025 Class : 1st
Year
Semester : 1
Course Name: Electrical Fundamentals
Course Code: ELE801

1) Explain the basic principle of series circuit.
Learning Outcomes
2) Find the total resistance for series circuits.
Upon completion of this lesson, the student should be able to:

In general the elements of an electrical circuit can be connected in different
methods. The two simplest of these are:
1) Series connection.
2) Parallel connection.
Introduction

Series Circuits
A series circuit is a circuit which consist of any number of elements
(resistances) joined one after one, so that there is only one path for
the current to flow through it therefore the current is equal at any
point in the circuit.

Total Voltage (Vt)
The total voltage is distributed across the resistors of the
series circuit.
Vt = V1 + V2 + V3

Total Voltage (Vt)
In general: The total voltage (Vt) for n number of resistors in
series circuit is equal to:
Vt = V1 + V2 + V3 + . . . . + Vn

Total Current (It)
The current is flow in one path, so the current is the same
in all resistors.
It = I1 = I2 = I3

Total Current (It)
It = I1 = I2 = I3 = . . . . = In
In general: The total current (It) for n number of resistors in
series circuit is equal to:

Total Resistance (Rt)
The total resistance is equal to sum of all resistances.
Rt = R1 + R2 + R3

Total Resistance (Rt)
Rt = R1 + R2 + R3 + . . . . + Rn
In general: The total resistance (Rt) for n number of resistors
in series circuit is equal to:

R1 + R2 + R3
=
Rt
Example (1)
15 Ω
=
Rt
R1
V = 30 v
R3
R2
4 Ω 6 Ω
5 Ω
4 + 5 + 6
=
Rt
Calculate the total resistance (Rt) for the shown circuit.

R1 + R2
=
Rt
Example (2)
6 Ω
=
Rt
4 + 2
=
Rt
R1
V = 30 v
R2
4 Ω 2 Ω

Exercise (1)
Answer
Rt = 18 Ω
R1 R2
10 Ω 8 Ω

Exercise (2)
Answer
Rt = 36 Ω
R1 R2
10 Ω 8 Ω
R3 R4
10 Ω 8 Ω

Exercise (3)
Calculate the resistance (R) for the shown circuit.
Rt = 30 Ω
Answer
R1 R2 R3
10 Ω 10 Ω 10 Ω

Remarks
Remark (1): If a lamp broken or disconnected, the
other lamps will stop working.

Remarks
Remark (2): The total resistance (Rt) in series circuit is
greater than the largest resistance in the circuit.
R1 R2 R3
5 Ω 10 Ω 20 Ω
For the circuit shown in the figure below:
R1 + R2 + R3
=
Rt
35 Ω
=
Rt
5 + 10 + 20
=
Rt

Think
R1 R2
(A)
R1 R2
(B)
For the shown circuits below, which circuit is Series circuit.
(B)
Answer

Think
For the shown circuit below, If the switch (S) is closed and suddenly
lamp (2) is defected. What will happened in the circuit?
Lamps (1) and (3) will stop working (OFF)
Answer
1 2 3
S

Summary
Vt = V1 + V2 + V3 + . . . . + Vn
Rt = R1 + R2 + R3 + . . . . + Rn
It = I1 = I2 = I3 = . . . . = In
In general: The for n number of resistors in series circuit:

References
1) Electrical technology, B. L. Theraja, A. K. Theraja, S. Chand and Company LTD,
first multicolor edition, 2005.
3) Electrical Wiring 1 / Technology, Ministry of education, Bahrain kingdom, 2002.
2) General Skills 1 / Technology, Ministry of education, Bahrain kingdom, 2010.
4) http://seventh4ruth.weebly.com/science/electrical-circuits
5) https://byjus.com/physics/difference-between-series-and-parallel-circuits/

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