FUNDAMENTALS OF ELECTRIC CIRCUITS

2. MY PROFILE
Name : Abdullah Al Mahfuj
Department : Textile.
Program : B.Sc. in Textile Engineering .
ID : 142014007
Green University of Bangladesh

3. Name of My Presentation
FUNDAMENTALS OF
ELECTRIC CIRCUITS

4. PRINCIPAL ELEMENTS OF
ELECTRICAL CIRCUITS
INDEPENDENT SOURCES
 The voltage/current sources that have the capability of
generating a prescribed voltage or current independent of
any other element within the circuit.
 These sources may output a constant voltage/current, or
they may output voltage/current that varies with time.

5. 1) Ideal Voltage Sources
An ideal voltage source is a two-terminal element that maintains
the same voltage across its terminals regardless of the current
flowing through it.
 Vt = constant, no matter what the load current is.
Vt
IL
Vo
L
t
+
-
V
o

6. 2) Ideal Current Sources
An ideal current source is a two-terminal element that maintains
the same current regardless of the voltage across its terminals.
 IS = constant, no matter what the load voltage is.
IO
VO
IS

7. DEPENDENT (CONTROLLED) SOURCES
 Dependent sources are whose output (current or voltage) is a
function of some other voltage or current in a circuit.
 The symbols typically used to represent dependent sources are in
the shape of a diamond.

8. BRANCH, NODE, LOOP, MESH
 Branch : any portion of a circuit with two terminals
connected to it.
 A branch may consist of one or more circuit elements.

9.  Node : the point of connection between two or more
branches.
 A node usually indicated by a dot in a circuit.
 Loop : any closed path through the circuit in which no node
is encountered more than once.

10.  Mesh : a loop that does not contain other loops.

11. CURRENT AND KIRCHHOFF’S
CURRENT LAW
Electric Current
 Electric current is defined as the time rate of change of
charge passing through a predetermined area.
 The units of current are called Amperes, where
1 Ampere (A) = 1 Coulomb/second (C/s).
 In order for current to flow, there must exist a closed
circuit.
EEE 1012 INTRODUCTION TO ELECTRICAL ENGINEERING

12. • In the circuit of this figure, the current i flowing
from the battery to the light bulb is equal to the
current flowing from the light bulb to the battery.
 no current (and therefore no charge) is “lost”
around the closed circuit. This principle is
known as Kirchhoff’s current law (KCL).

13. Kirchhoff’s Current Law (KCL)
 One of the fundamental laws of circuit analysis.
 Establish in 1874 by G.R. Kirchhoff.
 “The sum of the currents at a node must equal zero.”
𝑛=1
𝑁
𝑖 𝑛 = 0 𝑜𝑟
(𝐸𝑛𝑡𝑒𝑟𝑖𝑛𝑔 𝑐𝑢𝑟𝑟𝑒𝑛𝑡𝑠) = (𝐿𝑒𝑎𝑣𝑖𝑛𝑔 𝑐𝑢𝑟𝑟𝑒𝑛𝑡𝑠)

14.  Example of Kirchhoff’s current law:
At node 1:
−𝑖 + 𝑖1 + 𝑖2 + 𝑖3 = 0
𝑖 = 𝑖1 + 𝑖2 + 𝑖3
 In this illustration, currents
entering a node are defined as
negative and currents leaving
the node as positive.

15. VOLTAGE AND KIRCHHOFF’S
VOLTAGE LAW
Voltage
 The total work per unit charge associated with
the motion of charge between two points.
 The units of voltage are called Volts, where
1 Volts (V) = 1 Joule (J)/Coulomb (C).

16. Kirchhoff’s Voltage Law (KVL)
 The second fundamental laws of circuit analysis
introduced by G.R. Kirchhoff.
 The principle underlying KVL is that no energy is lost or
created in an electric circuit.
 In circuit terms, the sum of all voltages associated with
source must equal the sum of the load voltages.
 “The net voltage around a closed circuit is zero.”
𝑛=1
𝑁
𝑣 𝑛 = 0

17.  Example of Kirchhoff’s voltage law:
𝑣1 = 𝑣2 where
𝑣2 = 𝑣 𝑎𝑏 = 𝑣 𝑎 − 𝑣 𝑏
 In general, elements that provide
energy are referred as sources
and elements that dissipate energy
as loads.

18. ELECTRIC POWER
Power
 The electric power generated by an active element, or that
dissipated or stored by a passive element, is equal to the
product of the voltage across the element and the current
flowing through it.
 The units of power are called Watts (Joules/second).
𝑷 = 𝑽𝑰

19. MEASURING DEVICES
Ohmmeter:
The ohmmeter is a device
that, can measure the
resistance of the element.

20. Ammeter
The ammeter is a device that can
measure the current flowing through the
element.

21. Voltmeter
The voltmeter is a device that can
measure the voltage across a circuit
element.