16. What is a rectifier?
Ans:
A rectifier changes alternating
current into direct current. This process is called rectification. The three
main types of rectifier are the half-wave, full-wave, and bridge. A rectifier
is the opposite of an inverter, which changes direct current into alternating
current. HWR- The simplest type is the half-wave rectifier, which can be made
with just one diode. When the voltage of the alternating current is positive,
the diode becomes forward-biased and current flows through it. When the voltage
is negative, the diode is reverse-biased and the current stops. The result is a
clipped copy of the alternating current waveform with only positive voltage,
and an average voltage that is one third of the peak input voltage. This
pulsating direct current is adequate for some components, but others require a
more steady current. This requires a full-wave rectifier that can convert both parts
of the cycle to positive voltage.
17. Breifly explain the terms resistor, capacitor, inductor, transistor, diode ?
Ans:
A resistor is a two-terminal
electronic component that opposes anelectric current by producing a voltage
drop between its terminals in proportion to the current, that is, in accordance
with Ohm's law: V= IR.
A capacitor is an
electrical/electronic device that can store energyin the electric field between
a pair of conductors (called "plates"). The process of storing energy
in the capacitor is known as "charging", and involves electric
charges of equal magnitude, but opposite polarity, building up on each plate.
Capacitors are often used in electric and electronic circuits asenergy-storage
devices. They can also be used to differentiate between high-frequency and
low-frequency signals. This property makes them useful in electronic filters.
An inductor is a passive
electrical device employed in electrical circuits for its property of
inductance. An inductor can take many forms.
Diode is a two-terminal device.
Diodes have two active electrodes between which the signal of interest may
flow, and most are used for their unidirectional current property.
Transistor is a semiconductor
device commonly used to amplify or switch electronic signals. The transistor is
the fundamental building block of computers, and all other modernelectronic
devices. Some transistors are packaged individually but most are found in
integrated circuits.
18. Define conductor & Semi conductor?
Ans:
Conductor is a substance, body,
or device that readily conducts heat, electricity, sound, etc. Copper is a good
conductor of electricity.
A semiconductor is a solid
material that has electrical conductivityin between that of a conductor and
that of an insulator(AnInsulator is a material that resists the flow of
electric current. It is an object intended to support or separate electrical
conductorswithout passing current through itself); it can vary over that wide
range either permanently or dynamically.
19. What is Biasing?
Ans:
Biasing is a process of
connecting dc voltage to a device by which we can select the operating point of
the device. by biasing actually we select the operating point of the device.
20.What is Lenz law ?
Ans:
An induced current is always in
such a direction as to oppose the motion or change causing it whenever there is
an induced electromotive force (emf) in a conductor, it is always in such a
direction that the current it would produce would oppose the change which
causes the induced emf. If the change is the motion of a conductor through a
magnetic field, the induced current must be in such a direction as to produce a
force opposing the motion. If the change causing the emf is a change of flux
threading a coil, the induced current must produce a flux in such a direction
as to oppose the change.
21. What is Moore 's Law ?
Ans:
The prediction by Gordon Moore
(cofounder of the Intel Corporation) that the number of transistors on a
microprocessor would double periodically (approximately every 18 months).
22. What is a base station?
Ans:
Base station is a radio
receiver/transmitter that serves as the hub of the local wireless network, and
may also be the gateway between a wired network and the wireless network.
23. What is a repeater?
Ans:
A repeater is an electronic
device that receives a signal and retransmits it at a higher level and/or
higher power, or onto the other side of an obstruction, so that the signal can
cover longer distances without degradation.
24. What is Barkhausen criteria?
Ans:
Barkhausen criteria, without
which you will not know which conditions, are to be satisfied for oscillations.
“Oscillations will not be sustained if, at the oscillator frequency, the
magnitude of the product of the transfer gain of the amplifier and the
magnitude of the feedback factor of the feedback network ( the magnitude of the
loop gain ) are less than unity”. The condition of unity loop gain -Aβ = 1 is
called the Barkhausencriterion. This condition implies that | Aβ|= 1and that
the phase of - Aβ is zero.
25. What is attenuation?
Ans:
Attenuation is the reduction in amplitude and intensity of a signal.
Signals may attenuate exponentially by transmission through a medium, or by
increments calculated in electronic circuitry or set by variable controls.
Attenuation is an important property in telecommunications and ultrasound
applications because of its importance in determining signal strength as a
function of distance. Attenuation is usually measured in units of decibels per
unit length of medium (dB/cm, dB/km, etc) and is represented by the attenuation
coefficient of the medium in question.
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