1. Fundamentals of Electrical Circuits
C H A P T E R 2
Fundamentals of Electrical Circuits

2. Figure 2.4 (a) Automotive circuits

3. Figure 2.4 (b) Equivalent electrical circuit
batt
(b) + – I
head
tail
start
fan
locks
dash

4. Figure 2.8 (a) Electrical vehicle battery pack
DC-AC converter
(electric drive)
12 V
AC motor
(a) V
batt1
batt2
battn

5. Figure 2.8 (b) Illustration of KVL
Power
converter
and motor v
batt1 + –
drive
batt2
batt3
batt31
(b)

6. Figure 2.10 Various representations of an electrical system
Headlight
Car
battery + – R i v
Source
Load
(a) Conceptual
representation
Power flow
(b) Symbolic (circuit)
(c) Physical _ V S

7. Figure 2.18 Volt-ampere characteristic of a tungsten light bulb
0.1
0.2
0.3
0.5
0.4 – 20 30 40 50 60 10 i
(amps) v
(volts)
Variable
voltage
source
Current
meter +

8. Figure 2.20 The resistance elementv + – A l 1/
i-v
characteristic
Circuit symbol
Physical resistors
with resistance R.
Typical materials are
carbon, metal film.
R =

9. Figure 2.22 Resistor color codeb 4 3 2 1
Color bands
black
brown
red
orange
yellow
green 5
blue
violet
gray
white
silver
gold 6 7 8 9
10% 5%
Resistor value = ( ) 10 ;
= % tolerance in actual value

10. Figure 2.30 The current flows through each of
1.5 V + _ R v – i
flows through each of
the four series elements. Thus, by
KVL,
1.5 = 1 2 3
R 1
R 2
R 3 n N EQ
series resistors are equivalent to
a single resistor equal to the sum of
the individual resistances.

11. Figure 2.32 Parallel circuits+ – v
KCL applied at this node
The voltage
appears across each parallel
element; by KCL, i S = 1 2 3 N
resistors in parallel are equivalent to a single equivalent
resistor with resistance equal to the inverse of the sum of
the inverse resistances. R EQ n

12. Figure 2.36 Wheatstone bridge circuits1 v S a + _
(a) x b d
(b)

13. Figure 2.37 A force-measuring instrument1 v S 4 b a d c + – i h w
Beam cross section ,
bonded
to bottom surface F

14. Figure 2.38 Practical voltage source+ _ v –
Practical voltage
source =
lim
max
The maximum (short circuit)
current which can be supplied
by a practical voltage source is

15. Figure 2.39 Practical current source+ – v r
A model for practical current
sources consists of an ideal source in
parallel
with an internal
resistance.
Maximum output
voltage for practical
current source with
open-circuit load:
max =

16. Figure 2.41 Measurement of current+ _ v S
A series
circuit A
Symbol for
ideal ammeter
Circuit for the measurement
of the current i

17. Figure 2.42 Measurement of voltage1 + _ v S
A series
circuit V
Ideal
voltmeter
Circuit for the measurement
of the voltage i –

18. Figure 2.43 Models for practical ammeter and voltmeter

19. Figure 2.44 Measurement of power1 + _
Internal wattmeter connections 2 v – S i
Measurement of the power
dissipated in the resistor : P = W V A

20. Figure 2.45 Definition of a branchm A
Practical
ammeter
Ideal
resistor R v
A battery
A branch
Branch
voltage
current + – b i
Examples of circuit branches

21. Figure 2.47 Definition of a node
Examples of nodes in practical circuits
Node a
Node b v S i
Node c
Node

22. Figure 2.48 Definition of a loopv S R
1-loop circuit
3-loop circuit
(How many nodes in
this circuit?)
Note how two different loops
in the same circuit may in-
clude some of the same ele-
ments or branches. i 1 2

23. Figure 2.49 Definition of a mesh3 v S
Mesh 1 4 i
Mesh 3 5 2 + _
How many loops can you identify in this four-mesh circuit? (Answer: 14)