2. Electronics Theory
the branch of physics that deals with the emission and effects of
electrons and with the use of electronic devices
WHAT IS MATTER ?
Scientifically we define matter as all the "material" things
about us.
- Occupies space
- Has mass
3. Classes Of Matter
โข Solid
- Within a solid, atoms/molecules are relatively close together, or "rigid";
-of definite shape and volume; firm; neither liquid nor gaseous; "ice is water
in the solid state"
Liquid
- Liquid is a phase of matter in which the molecules are close together and
can move around slowly.
Gas
โข
โข
- Gas is a phase of matter in which the molecules are widely separated,
move around freely, and move at high speeds
4. Matter Composition
โA matter can be broken down into smaller piecesโ
ATOMS
a. Protons โ positively charged particles
b. Neutrons โ uncharged particles
c. Electrons โ negatively charged particles
6. The Law of Electromagnetic
Charges
โข The law states:
Like charges repel, and unlike charges attract
+
positive negative
-
Repel
+
positive
No attraction occurs
attraction
7. Conductor and Insulator
โข Conductor
- Materials which easily allow the flow of electrons from 1 point to
another.
ex. Iron, Copper, Gold
โข Insulator
- Materials which don't allow the flow of electrons from 1 point to
another.
ex . Plastic, rubber, wood
8. Difference Of Potential
+
-
If we connect a copper wire between two oppositely
charged bodies, an electron flow would result.
9. Difference Of Potential
โข Electric potential is the potential energy per unit of
charge.
โข Voltage is the difference of electrical potential between
two points of an electrical network, expressed in volts.
- -
+ +
PE PE PE PE
+
PE
-
PE
WIRE WIRE
Electrical Pressure
10. CURRENT
โข Electric current is by definition the flow of electric charge.
โข The unit of measure for this parameter is Ampere
wire
Active wire
Current is present
11. Types Of Current
โข Direct Current
- DirectCurrentisthemovementofanelectricalchargeinonedirection.
โข Alternating Current
-Analternatingcurrent(AC)isanelectricalcurrentwherethemagnitudeand
directionof thecurrent variescyclically
12. Measurement of Current
โข Themagnitudeofcurrentis measuredinAMPERES.Acurrentofoneampereis
saidto flowwhenonecoulombofchargepassesapointin onesecond.
Remember,onecoulombis equalto thechargeof6.28x10to the18thelectrons.
โข Frequently,theampereis muchtoolargeaunit formeasuringcurrent.Therefore,
theMILLIAMPERE(mA),one-thousandthofanampere,ortheMICROAMPERE
(ยตA), one-millionthofanampere,is used.Thedeviceusedto measurecurrentis
calledanAMMETERandwill bediscussedin detail in later.
Example: 1 Ampere
i - current
13. Resistor
โข Electricity, according to Benjamin Franklin, acts like a
fluid. It flows and has a measurable CURRENT . We can
restrict its flow by adding electrical friction. We say that
the restriction of electrical flow is called RESISTANCE
and that a device which causes such RESISTANCE is
called a RESISTOR . All materials, even the very best
CONDUCTORS demonstrate a certain amount of
RESISTANCE to electron flow.
14. RESISTOR IMAGE
VARIABLE RESISTOR
Resistors used in computers and other devices are typically much smaller,
often in surface-mount packages without wire leads.
CARBONFILMRESISTOR
This is the most general purpose, cheap resistor.
Usually the tolerance of the resistance value is ยฑ5%.
Power ratings of 1/8W, 1/4W and 1/2W are frequently used.
FIXED RESISTOR
CERAMICRESISTOR
POTENTIOMETER
16. From the top of the photograph
1/8W
1/4W
1/2W
Rough size
Rating
power
(W)
Thickness
(mm)
Length
(mm)
1/8 2 3
1/4 2 6
1/2 3 9
RESISTOR ANALYSIS
17. Resistance
โข In order to compare the resistance of various materials, we need to
have some standard unit of measurement. The unit of measurement
for resistance is called the Ohm , and is indicated by the Greek
letter Omega ( ฮฉ).
Less number of electrons are allowed to pass through
More current
RESISTANCE TO FLOW
18. Resistance
โข Although Ohm is the basic unit, Kilo Ohm and
Mega Ohm are frequently used. 1 Kilo Ohm (K
ฮฉ
) is equal to 1 thousand ฮฉ
. 1 Mega Ohm (M &
Omega) is equal to 1 million ฮฉ.
โข Ex
- 8 M Ohm = 8,000,000 Ohm = 8,000 K Ohm
19. Resistance
There are 4 factors that determine the resistance of a material
(1) Typeof Material
-The resistance of various types of materials are different. For
instance, gold is a better conductor of electricity than copper, and
therefore has less resistance.
(2) Length
-The resistance of a material is directly proportional to it's length.
The longer the material is, the more resistance it has. This is
because the electrons must flow through more material, and
therefore meets more friction over the entire distance.
20. Resistance
(3) Cross Sectional Area
- The resistance of a material is inversely proportional to the
cross sectional area of the material. This means that the thicker the
substance is across, the lower the resistance. This is because the
larger the cross sectional area is, the less friction there is over a
given length.
D
R = p L
A
Area is directly proportional to diameter
A = pie (R squared)
R = radius
D = 2R, diameter
21. Resistance
โข (4) Temperature
- In various types of materials, resistance can vary inversely or directly with
the temperature. This is because of the chemical properties of the material.
In Carbon, for instance, the resistance decreases as the temperature rises.
So we say it varies inversely. In copper, however, the opposite is true, with
the rise in temperature, we have a rise in the resistance.
Resistance then, is basically a form of friction which restricts the flow of an
electrical current. In basic science class, you learned that by putting your
hands together, and rubbing them quickly, your hands get warm. This is
because friction generates heat. Electrical friction - RESISTANCE - also
generates heat.
22. Direct Current Theory
โขThe current leaves the
battery at the negative
terminal, flows through
the bulb, and returns to the
positive terminal of the battery.
The electrons flow in one
direction. This is known in
electronics as DIRECT
CURRENT flow because the
electrons flow only in one direction.
23. Direct Current Theory
โข As long as we can follow the current from the negative terminal of
the battery throughout the entire circuit, and back to the positive
terminal, we have a COMPLETE CIRCUIT
In order to have any complete circuit, you are required to have at
least 3 parts:
โข
a. The SOURCE or SUPPLY of Voltage.
b. The LOAD which uses the source Voltage.
c. A complete path of connecting wires.
24. THE BASIC ELECTRIC CIRCUIT
โข LOAD
-is any device through which an electrical current flows and which
changes this electrical energy into a more useful form.
SWITCH
-which permits control of the electrical device, interrupts the current
delivered to the load.
SOURCE
-is the device which furnishes the electrical energy used by the
load.
โข
โข
25. SCHEMATIC REPRESENTATION
The schematic diagram
- is a "picture" of the circuit that uses symbols to represent the various
circuit components; physically large or complex circuits can be
shown on a relatively small diagram.
27. What happens to the path for
current when S1 is open as
shown in the figure?
Practice Reading Schematic Diagram
28. OHM'S LAW
โข Intheearlypartofthe19thcentury,GeorgeSimonOhmprovedby experimentthat
apreciserelationshipexistsbetweencurrent,voltage,andresistance.This
relationshipis calledOhm'slawandis statedasfollows:
โข The current in a circuit is DIRECTLY proportional to the applied
voltage and INVERSELY proportional to the circuit resistance.
Ohm's law may be expressed as an equation:
29. โข Asstatedin Ohm'slaw,currentis inverselyproportionalto resistance.This means,
astheresistanceinacircuitincreases,thecurrentdecreasesproportionately.
OHM'S LAW
31. Capacitor Theory
โข Capacitor โENERGY STORAGEโ
- A capacitor basically consists of two plates with an insulator in
between, although in practice the 'plates' are normally rolled up in a
can to save space. It can be used in a circuit to store charge for
small periods of time.
Plate I
Charges will attracted to other
side of the plate
Separation called Dielectric
Plate II
32. โขThe plate on the capacitor that attaches to
the negative terminal of the battery accepts
electrons that the battery is producing.
- The plate on the capacitor that attaches to
the positive terminal of the battery loses
electrons to the battery.
- Once it's charged, the capacitor has the same voltage as the battery1(.15.5Vvoltson the
battery means 1.5 volts on the capacitor).
For a small capacitor, the capacity is small. But large capacitors can hold quite a bit
of charge.
-
Capacitor Theory
Capacitance = is the property of a capacitor, a device, or an electric circuit that defines its
ability to store an electrical charge (or energy) when a given voltage is applied, measured in
farads (F)
33. โข Ceramic Capacitor
Capacitors
Electrolytic Capacitor
Ceramic capacitors are small in size and value, ranging from a few Pico Farads
to 1 ยตF. Not polarized, so either end can go to ground.
Electrolytic capacitors look like small cylinders and range in value from 1 ยตF to
several Farads. Very inaccurate and change in value as the electrolytic ages.
Polarized, cathode must go to ground. Cathode is marked with a minus sign on
case. Value is usually written on case.
Tantalum capacitors
Tantalum capacitors are similar in size to ceramic but can hold more charge, up
to several hundred ยตF. Accurate and stable, but relatively expensive. Usually
Polarized, anode is marked with a plus sign.
34. โข The unit of capacitance is a farad. A 1-farad capacitor can store one
coulomb (coo-lomb) of charge at 1 volt.
A coulomb is 6.25e18 (6.25 * 10^18, or 6.25 billion billion) electrons.
โข
Applications
-
-
Sometimes, capacitors are used to store charge for high-speed use. That's
what a flash does. Big lasers use this technique as well to get very bright,
instantaneous flashes.
Capacitors can also eliminate ripples. If a line carrying DC voltage has
ripples or spikes in it, a big capacitor can even out the voltage by absorbing
the peaks and filling in the valleys.
- A capacitor can block DC voltage. If you hook a small capacitor to a battery,
then no current will flow between the poles of the battery once the capacitor
charges
Capacitor Theory
35. โข Capacitors in Series:
Putting capacitors in series reduces the overall capacitance:
(1/C) = (1/C1) + (1/C2) + (1/C3) .....
Capacitor Theory
36. โข Capacitors in parallel:
โข Putting capacitors in parallel increases the total capacitance:
Capacitor Theory
Capacitors in parallel : C = C1 + C2 + C3
37. โขFor the network shown, determine the
equivalent capacitance of the network,
the charge on each capacitor, and the
potential difference across each.
We have a capacitor network to solve. Hence the first step is to
determine the equivalent capacitance of the network.
C' = C1 + C2 = 1 nf + 2 nf = 3 nf
1/Ceq = 1/C' + 1/6 nf = 1/3 + 1/6 = (2 + 1)/6 or Ceq = 2 nf
Capacitor Problem
3
0
V
6
n
f
2
n
f
1
n
f
39. โข An inductor is an energy storage device. It can be as simple as a
single loop of wire or consist of many turns of wire wound around a
special core. Energy is stored in the form of a magnetic field in
around the inductor.
Inductor Theory
40. Inductor Theory
โข The Basics
In a circuit diagram, an inductor is shown like this:
To understand how an inductor can work in a circuit, this figure is helpful:
Most of the current should follow the low-resistance
path through the loop. What happens instead is that
when you close the switch, the bulb burns brightly
and then gets dimmer. When you open the switch,
the bulb burns very brightly and then quickly
goes out.
41. Inductor Theory
The reason for this strange behavior is the inductor.
When current first starts flowing in the coil, the coil
wants to build up a magnetic field. While the field
is building, the coil inhibits the flow of current. Once
the field is built, current can flow normally through
the wire. When the switch gets opened, the
Magnetic field around the coil keeps current flowing
in the coil until the field collapses. This current
keeps the bulb lit for a period of time even though
the switch is open.
In other words, an inductor can store energy in its
magnetic field, and an inductor tends to resist any
change in the amount of current flowing through it.
Inductance = The property of an electric circuit
opposes a change in current
that
flow.
42. โข LT = L1 + L2
โข
โข
L= Inductance
Henry is the unit of measure for L
โข Parallel Inductors
(1/Ltotal) = (1/L1) + (1/L2) + (1/L3) .....
Series and Parallel Inductor
43. โข Diode
- diode is a component that restricts the direction of movement of
charge carriers. It allows an electric current to flow in one direction,
but essentially blocks it in the opposite direction.
Diode Theory
44. โข Rectifier.
- An electronic device with two
wires or terminals. A rectifier
allows electrical current to flow
through in only one direction
and is used for converting
alternating current into direct
current.
Diode Theory
Zener
45. โข
-
Rectifier.
An electronic device with two
wires or terminals. A rectifier
allows electrical current to flow
through in only one direction
and is used for converting
alternating current into direct
current.
Diode Theory
Zener Diode = Voltage
Regulator
