
Screw Gauge Viva Questions and Answers
November 30, 2019
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Screw Gauge Viva
Questions and Answers
Ans: Screw gauge.
(ii) What is meant by pitch of a screw gauge?
Ans: It is the distance advanced by the screw for one
complete rotation of the head.
(iii) The pitch of a screw is 1 mm and the number of
divisions on the head scale is 100. What is the least count?
Ans: Least count =
pitch/ No: of divisions on the head scale = 1/100 = 0.01 mm
(iv) What is zero error of a screw gauge?
Ans: If the zero of the head scale does not coincide with
the zero of the pitch scale when the end of the movable screw is in contact
with the stud, the screw gauge is said to have zero error.
(v) If the zero of the head scale is 5 divisions above the
line of graduation of the pitch scale when the gap is closed, what is the zero
error? What is the zero correction? Least count of the vernier = 0.01 mm
Ans: zero error = -5 x 0.01 = -0.05 mm and zero correction =
+0.05 mm
(vi) If the zero of the head scale is 5 divisions below the
line of graduation of the pitch scale when the gap is closed, what is the zero
error and correction? Least count = 0.01 mm
Ans: zero error = +5 x 0.01 = +0.05 mm and zero correction =
-0.05 mm
(vii) Why do we take a number of observations for the
diameter of a wire?
Ans: Even if the wire appears uniform it may not be true. So
to take the average value we take a set of readings
(viii) Why do you stop rotating the screw as soon as the
ratchet begins to turn between the fingers?
Ans: When the ratchet begins to turn, the two faces are in contact
or in contact with the body held between them. The device avoids undue pressure
on the screw.

Vernier Caliper Viva Questions and Answers
November 28, 2019
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Vernier Caliper Viva
Questions and Answers
(vi) Apparatus of Vernier Calipers
Ans: The vernier calipers, the given cylinder and the metallic rectangular block. The vernier calipers consists of a main scale and a small subscale called vernier scale. The main scale is usually graduated in mm. The vernier scale is a sub-scale which can slide along the main scale and can be fixed at any position with the help of a screw. Usually there will be 10 divisions on the vernier scale which are equivalent to 9 mm on the main scale. The main scale and the vernier scale are provided with jaws at their ends. When the jaws are in contact, the zero of the vernier coincides with the zero of the main scale.
(vii) Theory of Vernier Calipers
Ans: When a body is gripped between the jaws, the main scale reading (M.S.R) is the reading on the main scale just before the zero mark of the vernier scale and the vernier scale reading (V.S.R) is the number of the vernier division which coincides with some division of the main scale.
Ans: It is the smallest measurement that can be made with
the given instrument
(ii) What is meant by
least count of a vernier calipers?
Ans: It is the smallest length that can be measured with the
instrument and it is equal to the difference between a main scale division and
a vernier scale division.
(iii) The least count
of a vernier is 0.001 cm. What is the order upto which it can measure length
accurately?
Ans: It can measure accurately up to 10-3 cm.
(iv) What part of the
vernier calipers is the vernier scale?
Ans: The sliding scale along the main scale is called
vernier scale.
(v) Which is the
instrument you will use to measure the internal and external diameter of a
tube?
Ans: Vernier calipers
(vi) Apparatus of Vernier Calipers
Ans: The vernier calipers, the given cylinder and the metallic rectangular block. The vernier calipers consists of a main scale and a small subscale called vernier scale. The main scale is usually graduated in mm. The vernier scale is a sub-scale which can slide along the main scale and can be fixed at any position with the help of a screw. Usually there will be 10 divisions on the vernier scale which are equivalent to 9 mm on the main scale. The main scale and the vernier scale are provided with jaws at their ends. When the jaws are in contact, the zero of the vernier coincides with the zero of the main scale.
(vii) Theory of Vernier Calipers
Ans: When a body is gripped between the jaws, the main scale reading (M.S.R) is the reading on the main scale just before the zero mark of the vernier scale and the vernier scale reading (V.S.R) is the number of the vernier division which coincides with some division of the main scale.
If L. C is the least count of the vernier calipers,
Dimension measured = M.S.R + fraction = M.S.R + (V.S.R x L.C)
Volume of a cylinder = πr2l;
where r is the radius and l is the length of the cylinder.
Volume of the rectangular block = lbh;
where l, b and h are length, breadth and height of the
block.
If r is the internal radius and h is the depth of the
calorimeter,
Internal volume of the calorimeter = πr2h
(viii) Procedure of Vernier Calipers
To find the least count (LC) of the vernier calipers
The least count is the difference between a main scale
division and a vernier scale division. if (n — 1) main scale divisions are
divided into n vernier scale divisions then,
Least count = 1/n x 1 m.s.d
(a) To measure the dimensions of the cylinder
To find the length of the cylinder, it is gripped lengthwise
between the jaws. The main scale reading (M.S.R) immediately before the zero of
the vernier, and the division of the vernier (V.S.R) coinciding with any of the
main scale division are noted.
The length of the cylinder, l = M.S.R. + a fraction = M.S.R.
+ (V.S.R x L.C)
The experiment is repeated by keeping the vernier calipers
at different positions of the cylinder and the average length is calculated.
Similarly the mean diameter of the cylinder is determined.
The radius (r) of the cylinder is calculated from its diameter.
Volume of the cylinder = πr2l
(b) To find the volume of the given rectangular block of
known mass by measuring its dimensions with the vernier calipers and hence to
find its density.
The length (I), breadth (b) and the height (h) of the
rectangular block is determined as in the case of the measurement of the length
of the cylinder.
Volume of the rectangular block, V = l x b x h
If m is the mass of the block, its density, d = m/V
(c) To find the internal radius (r), depth (h) and volume
(V) of the calorimeter.
The upper ends of the jaws are put inside the calorimeter
and open them till each of them touches the inner wall of the calorimeter. The
main scale reading (M.S.R) and the vernier scale reading (V.S.R) are noted. The
inner diameter of the calorimeter = M.S.R + (V.S.R x L.C). The experiment is
repeated keeping the projections of the jaws tightly inside the calorimeter at
different positions and the average diameter is calculated. The inner radius r
of the calorimeter is calculated from its diameter.
The end of the main scale strip is kept on the upper edge of
the calorimeter. The vernier scale is pushed over the main scale till the tip
of the pointer attached to the back of the vernier touches the bottom of the
calorimeter. The M.S.R and V.S.R are noted. The depth h of the calorimeter =
M.S.R + (V.S.R x L.C). The experiment is repeated and the average depth is
calculated.
The volume V of the calorimeter is calculated from the equation,
V = πr2h

Microwave Engineering Viva Questions and Answers
November 27, 2019
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1. Give the range of frequency Band of
Microwave?
Microwaves
are signals in the form of electromagnetic waves with wavelengths ranging from
1m to 1mm. The frequency range of microwaves is from 3 GHz to 300 GHz. The
different frequency range bands are given below.
2. Why the Micro wave got the name as
microwaves?
The
meaning of microwaves is the small waves used for communication. Microwaves can
travel in straight line. So in satellite communication, microwaves are most
commonly used.
3. Discuss in detail about
Electromagnetic Frequency Spectrum?
The different ranges of frequency in
spectrum are given below:
4. List the major advantages of
Microwaves?
The major advantages of microwaves are:
a. Microwave Supports larger bandwidth, so
microwaves are widely used for point-to-point communications.
b. By using microwaves, it is possible
to attain antenna gain more.
c. Since the bandwidth is more, high
data transmission rates are possible.
d. As the frequency increases, the size
of antenna gets reduced
e. Low power consumption.
f. Effect of fading is less.
g. Gives effective reflection area in
the radar systems.
h. Used in Satellite and terrestrial
communications
i. Effective spectrum usage.
5. List the major applications of Microwaves?
Microwaves
can be used in wide variety of applications like Military, Food industry, radio
astronomy, medical applications, radar, semiconductor processing
techniques, spectroscopy etc.
6. Give the frequency band of Infrared
Rays (IR)?
The range of IR of the visible spectrum
at is from 700 nanometers (nm) to 1 millimeter (mm). This leads to a frequency
range of approximately 430 THz down to 300 GHz.
7. Discuss the band of visible Light?
The frequency band of light is from about
4 × 1014 to 8 × 1014 cycles per second, or hertz (Hz) and
wavelengths ranges from 740 nanometers (nm) or 2.9 × 10−5 inches, to
380 nm (1.5 × 10−5 inches).
8. Mention the band of X Rays?
The frequency band of X rays ranges from10
picometres to 10 nanometres, and the frequencies ranges from 30 petahertz to 30
exahertz (3×1016 Hz to 3×1019
Hz).
9. What is the band of gamma Rays?
The frequency range of gamma rays are
from 1020 - 1024 and the wavelength is in the range <
10 - 12 m
10. Define Phase velocity and Group
velocity?
The
velocity having a wave packet that travels is referred as group velocity. Whereas,
the velocity having the phase of a wave that travels is referred as phase
velocity.
11. The standard frequency used in
Microwave Oven for heating is?
The most modern microwave ovens use a
frequency of 2450 MHz (2.45 GHz) for heating.
12. Give the speed of Electromagnetic
waves in free space?
In free space, the electromagnetic waves
has a speed same as that of light, c = 3 x 108 m/s.
13. Explain about the propagation of EM
waves?
When
an electric charge (q) vibrates, the electromagnetic waves are generated. This generated
wave has both an electric and a magnetic component. Light waves are the example
of EM waves.
14. What is Faraday's law?
Faraday's law is
defined as a current that would be induced in a conductor which is exposed to a
varying magnetic field
15. Define Gauss law?
Gauss's
law is defined as the net flux of an electric field that is closed in an enclosed
surface is directly proportional to the enclosed electric charge.
16. Define Ampere's law?
Ampere’s
law states that “the magnetic field caused
by an electric current would be proportional to the size of electric current having
a constant of proportionality corresponding to the permeability of free space”.
17. Define TEM wave?
Transverse
electromagnetic (TEM) waves are those waves with a mode of propagation of
waves, while the electric and magnetic field lines are transverse (normal wave)
to the direction of propagation.
18. What you understand by Transverse
Electric (TE) wave?
TE
wave is an electromagnetic wave propagating in a medium, including free space,
or any other medium in such a manner that the electric field vector is directed
entirely transverse (perpendicular), to the general forward direction of
propagation.
19. What is mean by Transverse magnetic (TM)
waves?
TM
waves, also known as E waves are characterised by the fact that the magnetic
vector (H vector) is always perpendicular to the direction of propagation.
20. What you understand about EM wave?
Electromagnetic
waves (EM) waves are the type of waves which are created by a result of
vibrations between an electric field and a magnetic field. That is we can say
that the EM waves are composed of oscillating magnetic and electric fields.
21. Discuss about the need of
Transmission line?
The
main use of transmission line is to reduce power loss, dissipated as heat
because of the resistance of the conductors. For long distance power
transmissions, high voltage transmission lines are mostly used.
22. Discuss about the types of
transmission lines?
The different types of transmission
lines are:
a. Wave Guide
b. Fiber Optic
c. Balanced two wire
d. Co-axial cable
e. Microstrip
23. What is single stub matching?
In
order to match any complex load to a transmission line, stub matching is used. Stub
matching is group of shorted or opened segments of the line, which are connected
in parallel or in series with the line at an appropriate distances from the
load.
24. List the main advantages of
microwave integrated circuits (MIC)?
The
main advantages of MIC are:
a.
Many (thousands) of devices can easily be fabricated in a single MMIC at the
same time.
b.
Overall cost of MMIC is less.
c.
Mismatches in the MMIC between components are less.
d.
Since the distances between the components are less, the signal delay is less in
a MMIC.
e.
The wire bond reliability issues are less.
25. Discuss about reflection coefficient?
Reflection coefficient can be defined as
a parameter that describes how much of a wave is reflected by an impedance
discontinuity in the transmission medium. In other words, reflection
coefficient gives the amount of reflected waves in a transmission medium due to
the impedance mismatching.
26. Discuss about the different types of
losses in transmission lines?
The losses occurred in transmission
lines are mainly classified into three types. They are:
a. Copper Losses
b. Dielectric Losses
c. Radiation (Induction) Losses

Rectifier Viva Questions and Answers
November 26, 2019
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1.
Mention the difference of AC and DC power supply. Give the advantages of both?
The alternating current supply (Ac supply) is
sinusoidal function and is a function of time (t). That is as time changes, the
value of the AC supply also changes. But the DC supply is always constant for
every time (t).That is the value of dc current is constant with irrespective of
time. The dc current can be storable but the Ac current cannot be stored. For
long distance transfer, AC supply is suitable; the dc supply cannot be used for
long distances.

EDC Lab Viva Questions with Answers
November 23, 2019
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Electronic Devices and Circuits Lab Viva Questions with Answers
1.
Differentiate Electronics and Electrical Engg.?
We can say that electronics is the branch of
science which deals with vacuum tubes, semi conductor materials like diodes,
transistor etc. The maximum allowed voltage range of electronics engg is about
0 to 30 V. Electrical is the branch of science which deals with the currents in
conductors, in other words, we can say that electrical engg deals with 0 to 230
V, 50 Hz operating devices. Operation of devices like motors, generators etc
are included in electrical engg.
2.
Classify materials in terms of conductivity?
By the property of conduction of electricity,
materials can be mainly classified as conductors, semiconductors and
insulators. In conductors, the valance band (VB) and conduction band (CB)
overlaps each other (i.e., energy gap is zero), so the electrons can easily
move from valance band to the conduction band. Examples are Gold, Copper,
Silver etc. In insulators, the energy gap is very wide (about 3 to 5 eV) and
hence the electrons cannot flow from VB to CB. In semiconductors, the energy
gap is narrower so the electrons from VB can move to CB by absorbing energy.
The energy gap of Si is 1.1 eV and for Ge it is 0.7 eV.
3.
Differentiate Semiconductor and conductors?
Semiconductor has four electrons in its VB.
The energy gap of semiconductors is about 1 eV. So at normal condition the
electrons cannot move from VB to CB. By giving some external energy to the
electrons, electrons can move from VB to CB. The best semiconductors are Si,
Ge, etc. The conductors have more than four electrons in its VB. The energy gap
of conductors is 0 eV. So the electrons can easily move from VB to CB. Best
conductors are Ag, Al, Cu.
4.
Compare intrinsic and extrinsic Semiconductors?
Intrinsic semiconductors are the pure form of
semiconductors. At room temperature, the conductivity of intrinsic
semiconductor is zero. At room temperature, its VB is totally filled and the CB
is empty. When some heat energy is supplied (as temperature increases),
electrons can jump to CB and can move randomly. As temperature increases, the
conductivity increases and the resistivity decreases. Extrinsic semiconductors
are formed by intentionally adding impurities on it. At room temperature, the
extrinsic semiconductor is very little conductive. The impurities added can be
trivalent (resulting P type materials) or pentavalent (resulting N type
materials).
5.
Explain different types of extrinsic semiconductors and discuss their formation?
The extrinsic semiconductors are made of by
adding impurities on fourth group elements of periodic table (Si, Ge etc).
There are mainly two types of extrinsic semiconductors- P Type and N Type. P
types are formed by adding trivalent impurities (third group elements in
Periodic table such as arsenic, antimony, phosphorus) to the fourth group
elements. N type semiconductors are formed by adding pentavalent impurities
(fifth group elements like aluminum, boron etc) to the fourth group elements.
6.
Discuss the process of doping?
Simply we
can say that doping is the process of adding impurities. Extrinsic
semiconductors are made by doping process. The two types of doped semiconductor
materials are P type and N type materials.
7.
Discuss the process of formation of PN Junction?
A P-N junction (technically termed as diode)
is a piece of semiconductor material in which it’s one half is doped by P type
impurity and the other half is doped by N type impurity. P-N junction was
developed in the year 1936. The main advantage of P-N junction is it passes
current in only one direction. So we can say that PN junction act as a switch
in electronic circuits. The main application of PN junction is rectifier
circuits.
8.
Explain about cut in voltage (Barrier Potential)?
The cut in voltage is the minimum voltage in
which a PN junction starts its conduction. For Silicon diode, it is 0.7 Volts
and for Ge diode is 0.3 V. That is when the external applied voltage crosses
the barrier potential, the diode conducts electrons.
9.
Discuss about Forward bias and Reverse bias conditions?
If the externally applied voltage of the anode
(P) is greater than the cathode (N) voltage in a PN junction diode, the diode
is said to be in forward biased condition. If the anode voltage is less than
the cathode voltage, then the diode is in reverse biased condition.
10.
Compare between Diffusion and Drift currents?
The current formed by the diffusion of holes
or electrons is termed as the diffusion current. In other words we can say that
due to the non uniform concentration of charged particles, the transportation
of charge occurs and this current is termed as diffusion current. Diffusion
current doesn’t need an external applied electric field. Drift current is the
current occurred due to the effect of an externally applied electric field.
That is the motion of charged particles due to the effect of an externally
applied electric field. If there is no electric field, the drift current
becomes zero.
11.
Describe the meaning of 1N4007?
IN4007 is
actually represents a diode. The expansion of the diode is
IN means
it is a single junction diode
400x indicates
the voltage, current and power
4007 represents
the reverse voltage from 50V to 1000V, the maximum forward current is 1A
12. Justify the Diode current Equation?
The diode equation can be derived as
I=Io(e(V/ηVT)-1),
Where, Io is the Reverse saturation current,
and the value of η=1 for germanium,
and 2 for silicon.
13.
What you mean by Peak inverse voltage (PIV)?
PIV is
the maximum affordable reverse voltage of a diode. When the applied reverse
voltage exceeds the PIV, the PN junction gets damaged (diode goes to breakdown
condition). It is also known as Peak Reverse Voltage (PRV). The PIV is also
termed as reverse breakdown voltage.
14
Discuss about Reverse saturation current?
The reverse saturation current (Ico) is
produced due to the diffusive flow of minority charge carriers, when a diode is
at reverse biased condition. At R-B condition, the holes will get attracted to
the negative terminal of the applied cell and the electrons will get attracted
to the positive terminal of the cell. Hence the depletion width increases and
the flow of charges through the junction becomes zero. But there exists
thermally produced some electron-hole pairs. These thermally generated
electron-hole pairs are less in number and the electrons produced are repelled
by the –ve terminal and the holes are repelled by the +ve terminal. This will
cause a small current passes through the PN junction. This current is very
small and is almost constant.
15.
Discuss about the testing of diode by a multimeter?
The working condition of diode can be easily
tested by a multimeter. For testing a diode, the anode (P side) of the diode is
connected to the positive terminal of multimeter and the cathode (N side) of
the diode is connected to the negative terminal of the multimeter. If the
readed voltage is in the range of 0.3 to 0.7 Volts, then the diode is in good
condition.
16.
Mention the capacitive effects formed in a P-N junction.
There are mainly two types of capacitance
formed in a PN junction.
a. Diffusion Capacitance: The diffusion
capacitance occurs in forward biased condition.
b. Transition capacitance: Transition
capacitance occurs in the reverse biased condition.
17.Discuss
about the Break down condition, compare avalanche Break down and Zener Break down?
The breakdown occurs due to the impact of
ionization of electron-hole pair in a PN junction diode is termed as the
Avalanche breakdown.
At the reverse biased voltage condition, the
electron hole pair breaks in a zener diode and this breakdown is termed as
zener breakdown.
18.
Discuss the effect of temperature on reverse saturation current and barrier
voltage?
As the temperature increases, the reverse
saturation current also increases. As the temperature raise by 10 degrees, the
reverse saturation current doubles.
As the temperature increases, the barrier
voltage decreases. For every temperature increase of 1 degree, the barrier
voltage decreases by 2.5 mv
19.
Differentiate between static and dynamic resistances?
The ratio of voltage and current (V-I ratio)
at the Q-point(operating point) is the static resistance.
The inverse to the slop of the forward bias
characteristic curve at operating (Q point) is termed as the dynamic
resistance.
20.
Mention the applications of PN Diode and
Zener diode?
The main
applications of a PN junction diode are: Rectifier, clipper, clamper, switch etc.
Voltage
regulator circuit is the main application of zener diode.
21.What
is the major difference of PN junction and zener diode?
The main
difference of PN junction diode and zener diode is the PN junction is lightly
dopped and the zener diode is heavily dopped.
22.
Zener diode is not used in forward biased condition. justify your answer?
The response of a zener diode in forward bias
condition is same as that of a PN junction diode. So generally the zener diode
is used in reverse bias state with zener breakdown.
23.Discuss
the effect of temperature on Zener diode?
The effect
of temperature on zener diode depends on the breakdown voltage. If the
breakdown voltage (Vz) is less than 6V (breakdown voltage), Vz
is inversely proportional to temperature.
The
breakdown voltage Vz is directly proportional to temperature, if the
the breakdown voltage is greater than 6V
24.
Give the advantage of silicon over germanium?
The breakdown
voltage of silicon is more than germanium. The reverse saturation current of
silicon is less than that of germanium. Since the raw material is sand, silicon
diode is cheaper than germanium diode. The cut-off voltage of silicon diode is
0.7 V and that of germanium is 0.3V.
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