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1.When a bicycle is in motion,the force of friction exerted by the ground on the two wheels is such that it acts
(a) In the backward direction on the front wheel and in the forward direction on the rear wheel.
(b) In the forward direction on the front wheel and in the backward direction on the rear wheel.
(c) In the backward direction on both the front and rear wheels.
(d) In the backward direction on both the front and rear wheels.
Ans. (d)
2. A certain radioactive element A, has a half life = t seconds.
In (t/2) seconds the fraction of the initial quantity of the element so far decayed is nearly
(a) 29%
(b) 15%
(c) 10%
(d) 45%
Ans. (a)
3. Which of the following plots would be a straight line ?
(a) Logarithm of decay rate against logarithm of time
(b) Logarithm of decay rate against logarithm of number of decaying nuclei
(c) Decay rate against time
(d) Number of decaying nuclei against time
Ans. (b)
4. A radioactive element x has an atomic number of 100.
It decays directly into an element y which decays directly into element z.
In both processes a charged particle is emitted.
Which of the following statements would be true?
(a) y has an atomic number of 102
(b) y has an atomic number of 101
(c) z has an atomic number of 100
(d) z has an atomic number of 101
Ans. (b)
5. If the sum of the roots of the equation ax2 + bx + c=0 is equal to the sum of the squares of their reciprocals
then a/c, b/a, c/b are in
(a) AP
(b) GP
(c) HP
(d) None of these
Ans. (c)
6. A man speaks the truth 3 out of 4 times.
He throws a die and reports it to be a 6.
What is the probability of it being a 6?
(a) 3/8
(b) 5/8
(c) 3/4
(d) None of the above
Ans. (a)
7. If cos2A + cos2B + cos2C = 1 then ABC is a
(a) Right angle triangle
(b) Equilateral triangle
(c) All the angles are acute
(d) None of these
Ans. (a)
8. Image of point (3,8) in the line x + 3y = 7 is
(a) (-1,-4)
(b) (-1,4)
(c) (2,-4)
(d) (-2,-4)
Ans. (a)
9. The mass number of a nucleus is
(a) Always less than its atomic number
(b) Always more than its atomic number
(c) Sometimes more than and sometimes equal to its atomic number
(d) None of the above
Ans. (c)
10. The maximum KE of the photoelectron emitted from a surface is dependent on
(a) The intensity of incident radiation
(b) The potential of the collector electrode
(c) The frequency of incident radiation
(d) The angle of incidence of radiation of the surface
Ans. (c)
11. Which of the following is not an essential condition for interference
(a) The two interfering waves must be propagated in almost the same direction or
the two interfering waves must intersect at a very small angle
(b) The waves must have the same time period and wavelength
(c) Amplitude of the two waves should be the same
(d) The interfering beams of light must originate from the same source
Ans. (c)
12. When X-Ray photons collide with electrons
(a) They slow down
(b) Their mass increases
(c) Their wave length increases
(d) Their energy decreases
Ans. (c)
13. An electron emits energy
(a) Because its in orbit
(b) When it jumps from one energy level to another
(c) Electrons are attracted towards the nucleus
(d) The electrostatic force is insufficient to hold the electrons in orbits
Ans. (b)
14. How many bonds are present in CO2 molecule?
(a) 1
(b) 2
(c) 0
(d) 4
Ans. (d)
15. In a balanced chemical equation
(a) Atoms are conserved
(b) Molecules are conserved
(c) Moles are conserved
(d) Reactant and product molecules are preserved
Ans. (a)
16. How many grams of NaOH will react with 0.2 equivalent of HCl?
(a) 0.59
(b) 0.285
(c) 1.18
(d) none of these
Ans. (a)
17. Which of the following is least acidic
(a) Ortho-cresol
(b) Para-cresol
(c) Phenol
(d) Meta-cresol
Ans. (b)
18. In Reimer-Tiemann's reaction, the reaction intermediate is
(a) Carbene
(b) Dichloro carbene
(c) Carbonion
(d) Carbonium ion
Ans. (b)
19. Which of the following is most acidic?
(a) C2H5OH
(b) CH3CHOHCH3
(c) Ethanol
(d) CH3OH
Ans. (b)
20.A catalyst
(a)always slows down the reaction
(b)always starts a rection that would not have ocurred at all otherwise
(c)causes changes in the rate of the reaction
(d)changes the quantities of the products formed
Ans. (c)
21.The rate of the first order reaction depends on the
(a) Concentration of the reactant
(b) Concentration of the product
(c) Time
(d) Temperature
Ans. (d)
22. The most abundant element in the universe is
(a) Hydrogen
(b) Helium
(c) Oxygen
(d) Silicon
Ans. (a)
23. Integrate 3x + 5 / (x3-x2-x+1)
(a) 1/2 log | (x+1)/(x-1) | - 4/(x-1)
(b) log |2+tanx|
(c) -(1+logx)/x
(d) 2 log|(tanx)/(tanx+2)
Ans. A
24. If y=cos-1(cosx + 4sinx)/(17)1/2, then dy/dx is
(a) 0
(b) 1
(c)-1
(d) none of these
Ans. (b)
25. If the sum of n terms of two series of A.P are in the ratio 5n+4:9n+6 .find the ratio of their 13th terms
(a) 129/231
(b) 1/2
(c) 23/15
(d) None of the above
Ans. (a)
26. If the letters of the word "rachit" are arranged in all possible ways and these words are written
out as in a dictionary, what is the rank of the word "rachit".
(a) 485
(b) 480
(c) 478
(d) 481
Ans. (d)
27. Ravi's salary was reduced by 25%.Percentage increase to be effected to bring the salary
to the original level is
(a) 20%
(b) 25%
(c) 33 1/3%
(d) 30%
Ans. (c)
28. A and B can finish a piece of work in 20 days .B and C in 30 days and C and A in 40 days.
In how many days will A alone finish the job
(a) 48
(b) 34 2/7
(c) 44
(d) 45
Ans. (a)
29. How long will a train 100m long travelling at 72kmph take to overtake another train
200m long travelling at 54kmph
(a) 70sec
(b) 1min
(c) 1 min 15 sec
(d) 55 sec
Ans. (b)
30. What is the product of the irrational roots of the equation (2x-1)(2x-3)(2x-5)(2x-7)=9?
(a) 3/2
(b) 4
(c) 3
(d) 3/4
Ans. (a)
31. Which of the following parameters is the same for molecules of all gases at a given temperature?
(a) Mass
(b) Momentum
(c) Speed
(d) Kinetic energy
Ans. (d)
32. A solid is completely immersed in liquid. The force exerted by the liquid on the solid will
(a) Increase if it is pushed deeper inside the liquid
(b) Change if its orientation is changed
(c) Decrease if it is taken partially out of the liquid
(d) None of the above
Ans. (c)
33. Select the correct statements
(a) A simple harmonic motion is necessarily periodic
(b) An oscillatory motion is necessarily periodic
(c) A periodic motion is necessarily oscillatory
(d) All of the above
Ans. (a)
34. An elecrton is injected into a region of uniform magnetic flux density with the components
of velocity parallel to and normal to the flux.What is the path of the electron?
(a) Helix
(b) Parabola
(c) Circle
(d) Rectangle
Ans. (a)
35. A constant voltage is applied between the 2 ends of a uniform metallic wire.
Some heat is developed in it. The heat developed is doubled if
(a) both the length and radius of the wire are halved.
(b) both the length and radius of the wire are doubled
(c) the radius of the wire is doubled
(d) the length of the wire is doubled
Ans. (b)
36. If Young's double slit experiment is performed in water
(a) the fringe width will decrease
(b) the fringe width will increase
(c) the fringe width remains unchanged
(d) there will be no fringe
Ans. (a)
37. The shape of a spot of light produced when bright sunshine passes perpendicular
through a hole of very small size is
(a) Square, because the hole is a square
(b) Round, because it is an image of the sun
(c) Round with a small penumbra around it
(d) Square with a small penumbra
Ans. (b)
Select the alternative that logically follows from the two given statements.
38.
Some forms are books
All books are made of paper
(a) Some forms are made of paper
(b) Some forms are not made of paper
(c) No forms are made of paper
(d) None of the above
Ans. (a)
39.
All toffees are chocolates
Some toffees are not good for health
(a) Some chocolates are not good for health
(b) Some toffees are good for health
(c) No toffees are good for health
(d) Both (a) and (b)
Ans. (a)
The questions 40-46 are based on the following pattern.The problems below contain a question and two statements giving certain data. You have to decide whether the data given in the statements are sufficient for answering the questions.The correct answer is
(A) If statement (I) alone is sufficient but statement (II) alone is not sufficient.
(B) If statement(II) alone is sufficient but statement(I) alone is not sufficient.
(C) If both statements together are sufficient but neither of statements alone is sufficient.
(D) If both together are not sufficient.
(E) If statements (I) and (II) are not sufficient
40. What is the volume of a cubical box in cubic centimetres?
(I) One face of the box has an area of 49 sq.cms.
(II) The longest diagonal of the box is 20 cms.
Ans. D
41. Is z positive?
(I) y+z is positive
(II) y-z is positive
Ans. E
42. Is x>y ? x, y are real numbers?
(I) 8x = 6y
(II) x = y + 4
Ans. B
43. If a ground is rectangular, what is its width?
(I) The ratio of its length to its breadth is 7:2
(II) Perimeter of the playground is 396 mts.
Ans. C
44. If the present age of my father is 39 yrs and my present age is x yrs, what is x?
(I) Next year my mother will be four times as old as i would be.
(II) My brother is 2 years older than I and my father is 4 years older than my mother.
Ans. C
45. How many brothers and sisters are there in the family of seven children?
(I) Each boy in the family has as many sisters as brothers
(II) Each of the girl in the family has twice as many brothers as sisters
Ans. D
46. x is not equal to 0, is x + y = 0?
(I) x is the reciprocal of y
(II) x is not equal to 1
Ans. A
Following questions are based on letter's analogy.First pair of letters should have the same relationship as the second pair of letters or vice versa.
47. ? : BGLQ : : YDIN : VAFK
(a) EKNS
(b) DKMT
(c) DLMS
(d) EJOT
Ans. (d)
48. NLO : RPS : : ? : ZXA
(a) VUW
(b) VTR
(c) VTW
(d) TRP
Ans. (c)
49. If "segment" is coded as rffndou, then "ritual" is coded as
(a) shutbm
(b) qjutbk
(c) qhutbk
(d) qhubtk
Ans. (c)
50. If "football" is "cricket" ,"cricket" is "basketball" ,"basketball" is "volleyball","volleyball" is "khokho" and "khokho" is cricket, which is not a ball game?
(a) cricket
(b) football
(c) khokho
(d) basketball
Ans. (a)
51. Which of the following is a recursive set of production
(a) S --> a|A, A --> S
(b) S --> a|A, A --> b
(c) S -->aA, A-->S
(d) None of these
Ans. (c)
posted by prajwal @ 4:57 PM
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Aptitude Electronics
22.Once the thyristor starts conducting a forward current,its gate
losses control over
a)anode circuit voltage only
b)anode circuit current only
c)anode circuit voltage and current
d)anode circuit voltage and currentand time.ans. c
23.In a thyristor
a)Latching current IL is associated with the turn off porocess
b)both IL and IH is associated with the urn off processes
c)IH is associate with the turn off process and IL with the trun on
process
d)both IL and IH is associated with the turn on process
ans.c
24.A thyristor can be termed as
a)DC switch
b)AC switch
c)either a) or b)
d)square wave switchans.a
25.In a thyristor ,the magnitude of anode current will
a)increases if gate current is increased
b)decreases if gate current is decreased
c)increases if gate current is decreased
d) not change with any variation in gate current
ans.d
26.Turn on time of an SCR can be reduced by using a
a)rectangular pulse of high amplitude and narrow width
b)rectangular pulse of low amplitude and wide width
c)triangular pulse
d)trapezoidal pulse
ans.a
27.Turn on time of an SCR in series with the RL circuit can be reduced
by
a)increasing circuit resistance R
b)decreasing circuit resistance R
c)increasing circuit inductance L
d)decreasing circuit inductance L
ans.d
28.A forward voltage can be applied to SCR after its
a)anode current reduces to zero
b)gate recovery time
c)reverse recovery time
d)anode voltage reduces to zero
ans.b
28.Turn off time of an SCR is measured from the instant
a)anode current become zero
b)anode voltage become zero
c)anode voltage and anode current become zero at the same time
d)gate current becomes zero.
ans.a
29. In an SCR anode current flows over a narrow region near the gate
during
a)delay time td
b)rise time tr and spread time tp
c)td and tp
d)td and tr ans.d
30. The di/dt rating of an SCR is specified for its
a)decaying anode current
b)decaying gate current
c)rising gate current
d)rising anode current ans.d
31. The function of snubber circuit connected across an SCR is to
a)suppress dv/dt
b)increase dv/dt
c)decrease dv/dt
d)keep transient overvoltage at a constant value ans.a
32. In an UJT maximum value of charging resistance is associated with
a)peak point
b)valley point
c)any point between peak and valley points
after the valley points ans.a
33.For an UJT employed for triggering of an SCR stand off ratio n=0.64
and dc source voltage Vbb is 20V. The UJT would trigger when the
emitter voltage is
a)12.8V
b)13.1V
c)10v
d)5V ans.b
34. A metal oxide varistor (MOV) is used for protecting
a)gate circuits against overcurrents
b)gate circuits against overvoltages
c)anode circuits against overcurrents
d)anode circuits against overvoltages ans.d
35. For a pulse transformer, the material used for its core and the
possible turn ratio from primary to secondary are, respectively,
a)ferrite; 20:1
b)laminated iron; 1:1
c)ferrite; 1:1
d)powdered iron; 1:1 ans.c
36. In a dc dhoppers, if Ton is the on-period and f is the chopping
frequency, then output voltage in terms of input voltage Vs is given by
a)Vs.Ton/f
b)Vs.f/Ton
c)Vs/f.Ton
d)Vs.f.Ton ans.d
37. In dc choppers, the waveforms for input and output voltages are
respectively
a)discontinuous, continuous
b)both continuous
c)both discontinuous
d) continuous,discontinuous ans.d
38.In a dc choppers, per unit ripple is maximum when duty cycle is
a)0.2
b)0.5
c)0.7
d)0.9 ans.b
39. A load commutated chopper, fed from 200V dc source, has a constant
load current of 50A. For a duty cycle of 0.4 and a chopping frequency
of 2 KHz, the value of commutating capacitor and the turn-off time for
one thyristor pair are respectively
a)25 microF, 50 microsec
b)50 microF, 50 microsec
c)25 microF, 25 microsec
d)50 microF, 25 microsec ans.a
40. A dc chopper is fed from 100V dc. Its load voltage consists of
rectangular pulses of duration 1 msec in an overall cycle time of 3 msec.
The average output voltage and ripple factor for this chopper are
respectively,
a) 25V,1
b)50V,1
c)33.33V, 1.43
d)33.33V, 1 ans.c
41. In type-A chopper, source voltage is 100Vdc, on-period = 100
microsec, off period = 150 microsec and load RLE consists of R=2 Ohm, L= 5mH,
E= 10V. For continuous conduction, average output voltage and
averageoutput current for this chopper are respectively:
a)40V, 15A
b) 66.66V, 28.33A
c)60V, 25A
d)40V, 20A ans. a
42. If, for a single-phase half-bridge inverter, the amplitude of
output is Vs and the output power is P, then their corresponding values for
a single-phase full-bridge inverter are
a)Vs, P
b)Vs/2, P/2
c)2Vs, 2P
d)2Vs, P ans.c
43. A single phase full bridge inverter can operate in load-commutation
mode in case load consists of
a)RL
b)RLC underdamped
c)RLC overdamped
d)RLC critically damped ans.b
44. A single phase bridge inverter delivers power to a series connected
RLC load with R = 2 Ohm,
wL = 8 Ohm. For this inverter load combination, load commutation is
possible in case the magnitude of 1/wC in Ohm is
a)10
b)8
c)6
d)zero ans.a
45. In single pulse modulation of PWM inverters, third harmonic can be
eliminated if pulse width is equal to
a)30 degree
b)60 degree
c)120 degree
d)150 degree ans.c
46.In single pulse modulation of PWM inverters, fifth harmonic can be
eliminated if pulse width is equal to
a)30 degree
b)72 degree
c)36 degree
d)108 degree ans.b
47.In single pulse modulation of PWM inverters, the pulse width is 120
degree. For an input voltage of 220V dc, the r.m.s. value of output
voltage is
a)179.63 V
b)254.04 V
c)127.02 V
d)185.04 V ans.a
48. In a multiple pulse modulation used in PWM inverters, the
amplitudes of reference square wave and triangular carrier wave are respectively
1V and 2V. For generating 5 pulses per half cycle, the pulse width
should be
a)36 degree
b)24 degree
c)18 degree
d)12 degree ans.c
49. In a multiple pulse modulation used in PWM inverters, the
amplitudes and frequency for triangular carrier and square reference signal are
respectively 4 V, 6 KHz and 1V, 1 KHz. The number of pulses per half
cycle and pulse width are respectively
a)6, 90 degree
b)3,45 degree
c)4,60 degree
d)3,40 degree ans.b
50. Which of the following statement is correct in connection with
inverters:
a)VSI and CSI both require feedback diodes
b)only CSI require feedback diodes
c)GTO can be used in CSI
d)only VSI require feedback diodes ans.d
51. In a CSI, if frequency of output voltage is f HZ, then frequency of
voltage input to CSI is
a)f
b)2f
C)f/2
d)3f ans.b
52. In a sinusoidal pulse modulation used in PWM inverters, the
amplitudes and frequency for triangular carrier and sinusoidal reference
signal are respectively 5 V, 1 KHz and 1V, 50 Hz. If peak of the triangular
carrier coincides with the zero of the reference sinusoid, then the
modulation index and order of significant harmonics are
a)0.2,9 & 11
b)0.4,17 & 19
c)0.2,9 & 11
d)0.2,19 & 21 ans.d
53. In sinusoidal PWM, there are 'm' cycles os the triangular carrier
wave in the half cycle of the reference sinusoid signal. If zero of the
reference sinusoid coincides with zero/peak of the triangular carrier
wave, then number of pulses generated in each half cycle are
respectively,
a)(m-1)/m
b)(m-1)/(m-1)
c)m/m
d)m/(m-1) ans.a
54. A single-phase CSI has capacitor C as the load. For a constant
source current, the voltage across the capacitor is
a) square wave
b) triangular wave
c) step-function
d) pulsed wave ans.b
55. A single phase full bridge VSI has inductor L as the load. For a
constant source voltage, the current through the inductor is
a) square wave
b) triangular wave
c)sine wave
d) pulsed wave ans.b
56. A single phase voltage controller feeds an induction motor (A) and
a heater (B)
a)in both the loads, fundamental and harmonics are useful.
b)in A only fumdamental and in B only harmonics are useful
c)in A only fumdamental and in B harmonics as well as fundamental are
useful
d)in A only harmonics and in B only fundamental are useful
ans.c
57. A single phase voltage controller, using 2 SCRs in antiparallel is
found to be operating as a controlled rectifier, this is because
a)load is R and pulse gating is used
b)load is R and high frequency carrier gating is used
c)load is RL and pulse gating is used
d)load is RL and continuous gating is used
ans.c
58. In dc chopper, for chopping period T, the output voltage can be
controlled by FM by varying
a)T keeping Ton constant
b)T keeping Toff constant
c)(a) & (b)
d)Toff keeping T constant
ans.c
59. For dynamic equilizing circuit used for series connected SCR the
choice of capacitor is based on
a)reverse recovery characteristics
b)turn on characteristics
c)turn off characteristics
d)rise time characteristics
ans.a
60. When an UJT is used for triggering an SCR the wave shape of the
voltage obtained from UJT circuit is a
a)sine wave
b)sawtooth wave
c)trapezoidal wave
d)square wave
ans.b
61. An UJT exhibits negative resistance region
a)before the peak point
b)between peak and valley points
c)after valley points
d)both (a) & (c)
ans.b
62. In synchronized UJT triggering of SCR, voltage Vc across capacitor
reaches UJT threshold voltage thrice in each half cycle so that there
are three firing pulses during each half cycle. The firing angle of SCR
can be controlled
a)once in each half cycle
b)thrice in each half cycle
c)twice in each half cycle
d)four times in each half cycle
ans. a
63. A thyristor, when triggered, will change from forward bloking state
to conduction state if its anode to cathode voltage is equal to
a) peak repetitive off-state forward voltage
b) peak working off-state forward voltage
c) peak working off-state reverse voltage
d)peak non repetitive offset forward voltage
ans. b
64.Gate characteristic of a thyristor
a)is a straight line
b)is of the type Vg=a+b.Ig
c)is a curve between Vg and Ig
d)has spread between two curves of Vg-Ig
ans.d
65.Surge current rating of specifies the maximum
a)repetitive current with sine wave
b)non repetitive current with rectangular wave
c)non repetitive current with sine wave
d)repetitive current with rectangular wave
ans. c
66.For an SCR,di/dt is achieved through the use of
a)RL in series with SCR
b)RC across SCR
c)L in series with SCR
d)L across SCR
ans.b
67.The object of connecting resistance and capacitance across gate
circuit is to protect the SCR gate against
a)over voltage
b)dv/dt
c)noise signal
d)over currents
ans.c
68.A metal oxide varistor(MOV) is used for protecting
a)gate circuit against over currents
b)gate circuit against over voltages
c)anode circuit against over currents
d)anode circuit against over voltages
ans.d
69.For a pulse transformer, the material used for its core and the
possible turn-ratio from the primary to secondary are respectively
a)ferrite;20:1
b)laminated iron,1:1
c)ferrite;1:1
d)powdered iron;1:1
ans.c
70.SCR can be turned ON by
a)applying anode voltage at a sufficiently fast rate
b)applying sufficiently large anode voltage or gate current
c)increasing the temperature of SCR to a sufficiently large value
d)all of the above
ans.d
71.During the forward blocking of two series connected SCRs ,a
thyristor with
a)high leakage impedence shares lower voltage
b)high leakage impedence shares higher voltage
c)low leakage impedence shares lower voltage
d) both b) and c)
ans.d
72.Thyristor A has rated gate current of 2 and thyristor B a rated
current of 100mA
a)A is GTO and B is conventional SCR
b)B is GTO and A is conventional SCR
c)A may operaten as a transistor
d)both a) & c)
ans.d
73.A resistor connected across the gate and cathode of an SCR increases
its
a)dv/dt rating
b)turn off time
c)both a) and b)
d)only a)
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