2. What is Voltage?
Voltage, also called electromotive force, is a
quantitative expression of the potential
difference in charge between two points in an
electrical field.
Voltage is symbolized by an uppercase italic
letter V or E
The standard unit is the volt
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3. Voltage
One volt will drive one coulomb (6.24 x 1018)
charge carriers, such as electrons, through
a resistance of one ohm in one second
Voltage can be direct or alternating
A direct voltage maintains the
same polarity at all times
In an alternating voltage, the polarity reverses
direction periodically
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4. Relation
Voltage is the difference in charge between
two points
Current is the rate at which charge is flowing
Resistance is a material's tendency to resist
the flow of charge
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7. Coulomb
The coulomb (symbol: C) is the International
System of Units (SI) unit of electric charge
It is the charge transported by a constant
current of one ampere in one second:
1C= 1A.1s
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8. Traditional Definition
Voltage, electric potential difference, electric pressure or
electric tension is the difference in electric potential
between two points per unit electric charge
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9. Feed Forward
Feed-forward, is a term describing an
element or pathway within a control system
that passes a controlling signal from a source
in its external environment, often a command
signal from an external operator, to a load
elsewhere in its external environment
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10. Negative feed Forward
Negative feedback (or balancing feedback)
occurs when some function of the output of a
system, process, or mechanism is fed back in
a manner that tends to reduce the fluctuations
in the output, whether caused by changes in
the input or by other disturbances
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11. Voltage Regulator
A voltage regulator is an electronic circuit that
provides a stable dc voltage independent of
the load current, temperature and ac line
voltage variations
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12. Voltage Regulator
Voltage regulator, any electrical or electronic
device that maintains the voltage of a power
source within acceptable limits
The voltage regulator is needed to keep
voltages within the prescribed range that can
be tolerated by the electrical equipment using
that voltage
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13. Applications
Such a device is widely used in motor
vehicles of all types to match the output
voltage of the generator to the electrical load
and to the charging requirements of the
battery
Voltage regulators also are used in electronic
equipment in which excessive variations in
voltage would be determinal
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14. Applications
Voltage regulators perform the same function
in large-scale power-distribution systems as
they do in motor vehicles and other machines;
they minimize variations in voltage in order to
protect the equipment using the electricity
In power-distribution systems the regulators
are either in the sub-stations or on the feeder
lines themselves
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15. Variable Resistances
Electronic voltage regulators utilize solid-state
semiconductor devices to smooth out
variations in the flow of current
In most cases, they operate as variable
resistances; that is, resistance decreases
when the electrical load is heavy and
increases when the load is lighter
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16. Types
Two types of regulators are used:
Step regulators:
In which switches regulate the current supply
Induction regulators :
In which an induction motor supplies a
secondary, continually adjusted voltage to
even out current variations in the feeder line
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17. Voltage Regulator in System Unit
The quality of the voltage regulator circuit is one of the
best ways to have an idea about the overall
motherboard quality and life-span for several reasons.
A good voltage regulator won’t have any fluctuations or
noise on its outputs, providing the CPU and other
components with a clean and stable voltage, allowing
them to work perfectly.
A bad voltage regulator can lead to fluctuations or
noise on the voltage that will lead to malfunctions like
the computer crashing
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18. Contd.
If this circuit uses low-quality electrolytic
capacitors they will leak, swell or even
explode
Frequently when a motherboard dies it is this
circuit that goes bad
Having a good-quality voltage regulator
circuit will ensure that you will have a stable
system that will last for years.
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19. Contd.
Recognizing this circuit is pretty easy. Since it
is the only circuit on the motherboard that
uses chokes (a kind of coil), locate the chokes
and you will have located the voltage
regulator circuit.
Usually this circuit is around the CPU socket,
but you will find some chokes spread on the
motherboard
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23. Display Screen
A surface area upon which text, graphics and
video are temporarily made to appear for
human viewing
Types of it include:
CRT
Flat Panel
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24. CRT
The cathode ray tube (CRT) is a vacuum
tube that contains one or more electron guns and
a phosphorescent screen, and is used to display
images
It modulates, accelerates, and deflects electron
beam(s) onto the screen to create the images
The images may represent
electrical waveforms(oscilloscope), pictures
(television, computer monitor), radar targets, or
others
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26. Disadvantages
They took much space
They took much electricity
They got heat up early
High refresh rate
High radiation emission
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27. LCD
LCD stands for Liquid Crystal Display
A liquid-crystal display (LCD) is a flat-panel
display or other electronically modulated
optical device that uses the light-modulating
properties of liquid crystals.
Liquid crystals do not emit light directly,
instead using a backlight or reflector to
produce images in color or monochrome
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28. LCD
LCDs are available to display arbitrary images
or fixed images
They use the same basic technology, except
that arbitrary images are made up of a large
number of small pixels, while other displays
have larger elements.
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29. Working of LCD
It is combination of two states of matter, the
solid and the liquid
LCD uses a liquid crystal to produce a visible
image
Liquid crystal displays are super-thin
technology display screen that are generally
used in laptop computer screen, TVs, cell
phones and portable video games.
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30. LCD
Liquid crystal display is composed of several
layers which include two polarized panel filters
and electrodes
LCD technology is used for displaying the image
in notebook or some other electronic devices like
mini computers
Light is projected from a lens on a layer of liquid
crystal. This combination of colored light with the
grayscale image of the crystal (formed as electric
current flows through the crystal) forms the
colored image. This image is then displayed on
the screen.
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32. Construction Facts of LCD
Simple facts that should be considered while
making an LCD:
1.The basic structure of LCD should be
controlled by changing the applied current.
2.We must use a polarized light.
3.Liquid crystal should able be to control and to
transmit or can also able to change the
polarized light.
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33. Principle
The principle behind the LCDs is that when an
electrical current is applied to the liquid crystal
molecule, the molecule tends to untwist
This causes the angle of light which is passing through
the molecule of the polarized glass and also cause a
change in the angle of the top polarizing filter
As a result a little light is allowed to pass the polarized
glass through a particular area of the LCD. Thus that
particular area will become dark compared to other.
The LCD works on the principle of blocking light.
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34. Advantages
Since LCD screens do not use phosphors, they do
not suffer image burn-in when a static image is
displayed on a screen for a long time
The LCD screen is more energy-efficient and can
be disposed of more safely than a CRT can.
Its low electrical power consumption enables it to
be used in battery-powered electronic equipment
more efficiently than CRTs can be
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35. Disadvantages
Require additional light sources
Range of temperature is limited for operation
Low reliability
Speed is very low
LCDs need an AC drive
LCDs are susceptible to image persistence
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36. Applications
Liquid crystal thermometer
Optical imaging
The liquid crystal display technique is also
applicable in visualization of the radio
frequency waves in the waveguide
Used in the medical applications
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37. LED
LED stands for Light Emitting Diode
A light-emitting diode (LED) is a two-
lead semiconductor light source It is a p–n
junction diode that emits light when activated
When a suitable voltage is applied to the
leads, electrons are able to recombine
with electron holes within the device,
releasing energy in the form of photons
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38. Contd.
This effect is called electroluminescence, and
the color of the light (corresponding to the
energy of the photon) is determined by the
energy band gap of the semiconductor
LEDs are typically small (less than 1 mm2)
and integrated optical components may be
used to shape the radiation pattern
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40. Advantages
Following are different advantages of LED
1.Reduced heat
2.Life time is better than others
3.They are more durable
4.They have more light output
5.Unlike others they don’t release mercury in air
when disposed off
6.They gives instant lightening
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41. Disadvantages
LED’s can shift color due to age and
temperature
They have high cost
LED performance largely depends on
correctly engineering the fixture to manage
the heat generated by the LED
They need correct voltage continuously
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