This presentation contains notes for RLC circuits in EEE subject in enghineering

1. Resistors
 Resistors can be either fixed
or variable in value
 Fixed resistors come in a
variety of different shapes,
sizes and forms
 Axial lead resistors have the
value of resistance printed
on them or as a colour code
 Surface mount resistors
have a numerical code
indicating a value
 All resistors have a tolerance
value

2. Resistors
 Variable resistors
are called
potentiometers
 There is a fixed
value of resistance
between two
terminals
 The moving part of
the potentiometer is
called the wiper

3. Resistors
 Four band resistor
colour code
 1st band provides the
first digit of the code
 2nd band provides the
second digit of the code
 3rd band is the
multiplier
 4th band indicates the
tolerance value

4. Resistors Colour Coding

5. Resistors
Resistor colour code calculation
 The first band red has a value
of 2
 The second band purple has a
value of 7
 The third band has a multiplier
of x 10
 The last band indicates a
tolerance value of +/-5%
 Resistance value is 270Ω +/-5%
2
7
x10
+/-5%

6. Capacitors
 A basic capacitor has two parallel plates
separated by an insulating material
 A capacitor stores an electrical charge
between the two plates
 The unit of capacitance is Farads (F)
 Capacitance values are normally smaller,
such as µF, nF or pF

7. Capacitors
 Basic capacitor construction
Dielectric
material
Plate 1
Plate 2
The dielectric
material is an
insulator therefore
no current flows
through the
capacitor

8. Capacitors
Storing a charge between
the plates
 Electrons on the left
plate are attracted
toward the positive
terminal of the voltage
source
 This leaves an excess of
positively charged holes
 The electrons are
pushed toward the right
plate
 Excess electrons leave a
negative charge
+ -
+
_
+ _

9. Capacitors
Types of capacitors
 The dielectric material
determines the type of
capacitor
 Common types of
capacitors are:
 Mica
 Ceramic
 Plastic film

10. Capacitors
 Some capacitors are
polarised, they can
only be connected
one way around
 Electrolytic
capacitors are
polarised

11. Capacitors
 Variable capacitors are
used in communication
equipment, radios,
televisions and VCRs
 They can be adjusted by
consumers by tuning
controls
 Trimmers are internal
adjusted capacitors
that a consumer cannot
adjust

12. Capacitors
 These variable
capacitors would be
difficult to squeeze
into your mobile
phone and iPod
 Current technology
uses semi-conductor
variable capacitors
called varactors
(varicaps)

13. Capacitors
 The capacitance in a
varactor is created
when a purpose diode is
reversed biased
 Adjusting the reverse
bias alters the
capacitance value
 A simple radio receiver
using varactor
http://www.microst.it

14. Capacitors
 Composed of two conductive plates separated
by an insulator (or dielectric).
 Commonly illustrated as two parallel metal plates
separated by a distance, d.
C = e A/d
where e = er eo
er is the relative dielectric constant
eo is the vacuum permittivity

15. Effect of Dimensions
 Capacitance increases with
 increasing surface area of the plates,
 decreasing spacing between plates, and
 increasing the relative dielectric constant of the
insulator between the two plates.

16. Types of Capacitors
 Fixed Capacitors
 Nonpolarized
 May be connected into circuit with either terminal of
capacitor connected to the high voltage side of the circuit.
 Insulator: Paper, Mica, Ceramic, Polymer
 Electrolytic
 The negative terminal must always be at a lower voltage
than the positive terminal
 Plates or Electrodes: Aluminum, Tantalum

17. Nonpolarized
 Difficult to make nonpolarized capacitors that
store a large amount of charge or operate at
high voltages.
 Tolerance on capacitance values is very large
 +50%/-25% is not unusual
http://www.marvac.com/fun/ceramic_capacitor_codes.a
spx
PSpice Symbol

18. Electrolytic
Pspice Symbols Fabrication
http://www.digitivity.com/articles/2008/11/choosing-the-right-
capacitor.html

19. Variable Capacitors
 Cross-sectional area is changed as one set of
plates are rotated with respect to the other.
http://www.tpub.com/neets/book2/3f.htm
PSpice Symbol

20. Energy Storage
 Charge is stored on the plates of the capacitor.
Equation:
Q = CV
Units:
Farad = Coulomb/Voltage
Farad is abbreviated as F

21. Capacitors in Parallel

22. Ceq for Capacitors in Parallel
i
4
3
2
1
eq
4
3
2
1
4
4
3
3
2
2
1
1
4
3
2
1
C C
C
C
C
dt
dv
C
i
dt
dv
C
dt
dv
C
dt
dv
C
dt
dv
C
i
dt
dv
C
i
dt
dv
C
i
dt
dv
C
i
dt
dv
C
i
i
i
i
i
i
eq
in
in
in


















23. Capacitors in Series

24. Summary
 Capacitors are energy storage devices.
 An ideal capacitor act like an open circuit at steady state when a DC
voltage or current has been applied.
 The voltage across a capacitor must be a continuous function; the
current flowing through a capacitor can be discontinuous.
 The equations for equivalent capacitance for
capacitors in parallel capacitors in series
1
1
1








 
S
s s
eq
C
C



P
p
P
eq C
C
1



1
1
t
t
C
C
C
C
o
dt
i
C
v
dt
dv
C
i

25. Magnetic fields
 A magnetic field may be represented by a mathematical
description of the magnetic influence of electric currents and
magnetic materials. The magnetic field at any given point is
specified by both a direction and a magnitude (or strength); as such
it is a vector field
 Magnetic fields are produced by moving electric charges and the
intrinsic magnetic moments of elementary particles
Compasses reveal the direction
of the local magnetic field.
Magnetic field of an ideal
cylindrical magnet with its axis of
symmetry inside the image plane.
Electromagnetism

26. Magnetic fields

27. Magnetic fields
 The magnetic flux is measured in webers (Wb) and the
applied symbol is the capital Greek letter phi Φ
Flux density

28. Inductors
 Inductors are coils of various dimensions designed to
introduce specified amounts of inductance into a
circuit.
 The inductance of a coil varies directly with the magnetic
properties of the coil.
 Ferromagnetic materials, are frequently employed to
increase the inductance by increasing the flux linking the
coil.
 Inductance is measured in Henries (H)
 1 Henry is the inductance level that will establish a voltage
of 1 volt across the coil

29. Inductors
 An inductor is a passive two-terminal electrical
component that stores energy in its magnetic field.
 An inductor is typically made of a wire or other conductor
wound into a coil, to increase the magnetic field.
 When the current flowing through an inductor changes,
creating a time-varying magnetic field inside the coil, a voltage
is induced, according to Faraday's law of electromagnetic
induction
 Inductors are one of the basic components used in
electronics where current and voltage change with time, due to
the ability of inductors to delay and reshape alternating
currents.

30. Inductors
Inductor symbols

31. FARADAY’S LAW OF
ELECTROMAGNETIC INDUCTION
If a conductor is moved through a
magnetic field so that it cuts magnetic
lines of flux, a voltage will be induced
across the conductor
The greater the number of flux lines cut per
unit Time or the stronger the magnetic field
strength, the greater will be the induced voltage
across the conductor.
Increase the number of magnetic flux lines by
increasing the speed with which the conductor
passes through the field
Equation for voltage induced across a
coil if a coil of N turns is placed in the
region of a changing flux

32. Faraday’s law induced voltage equation
If the flux linking the coil ceases to change
= is the instantaneous change in flux (in webers)
N = number of turns of the coil
&
Equation for inductance of the coils
N = number of turns
µ = permeability of the core
A = area of the core
in square meters
l = the mean length of the core in meters.
µ is not a constant but
depends on the level of B
and H, since µ = B/H

33. Substituting µ = µr µo into Equation we get
Lo is the inductance of the coil with an air core