Electrical Engineering test questions for exams and entrance - 7
(1) By an 8085 microprocessor, the instructions given below have been executed.
ADDRESS INSTRUCTIONS
6010 LXI H, 8AY9 H
6013 MOV A, L
6015 ADDH
6016 DAA
6017 MOV H, A
6018 PCHL
The next instruction will be fetched from address
(A) 6019
(B) 6379
(C) 6259
(D) 6240
View Answer / Hide Answer(2) Local oscillators in a BPSK signal detector, has a fixed phase error of 20° that deteriorates SNR at the output, by a factor of
(A) cos70°
(B) cos90°
(C) cos120°
(D) cos45°
View Answer / Hide Answer(3) Rated load torque at rated speed is delivered by a dc cumulatively compounded motor and if series field is short-circuited then,
(A) The armature current will decrease and speed will increase
(B) The armature current will increase and speed will decrease
(C) The armature current and speed both will decrease.
(D) The armature current and speed both will increase
View Answer / Hide AnswerANSWER: The armature current and speed both will increase
(4) In the circuit shown below it is desired to have a constant direct current i (t) through an ideal inductor L. The nature of the voltage source v (t) must be
(A) Linearly increasing voltage
(B) An ideal impulse
(C) An exponentially increasing voltage.
(D) Constant voltage
View Answer / Hide Answer(5) Consider the circuit shown below. When viewed from the terminal AB this circuit can be reduced to an equivalent circuit at single voltage source in series with a single resistor with
the parameters as
(A) 10 volt source in series with 10ohm resistor
(B) 5 volt source in series with 10ohm resistor
(C) 15 volt source in series with 15ohm resistor
(D) 1 volt source in series with 2.4ohm resistor
View Answer / Hide AnswerANSWER: 1 volt source in series with 2.4ohm resistor
(6) A feedback control system has characteristic equation as 2s
4 + s
³ + 3s
² + 5s + 10 = 0. How many roots are present in the right half of s plane?
(A) 3
(B) 2
(C) 1
(D) 0
View Answer / Hide Answer(7) For power measurement a two-wattmeter method is used. What should be the load pf angle for one of the wattmeter to show negative reading?
(A) Less than 60°
(B) Less than 45°
(C) Greater than 60°
(D) Greater than 45°
View Answer / Hide Answer(8) When a sinusoidal current i (t) = 10 sin ωt is passed through a rectifier type ammeter, it indicates a current reading of 7.07 A. The waveform shown below is of current that is
passed through a rectifier type instrument. The true RMS current in the circuit is
(A) 7.07 A
(B) 3.20 A
(C) 1.26 A
(D) 5.87 A
View Answer / Hide Answer(9) For the K map shown below the minimal product of sum function described is
(A) A’C’
(B) A + C
(C) AC
(D) A’ + C’
View Answer / Hide Answer(10) Consider a 3-phase, 4-pole squirrel cage induction motor that has 36 stator and 28 rotor slots. The number of phases in the rotor is
(A) 7
(B) 10
(C) 3
(D) 5
View Answer / Hide Answer(11) The torque speed characteristic of an electric motor with constant output power is in the form of
(A) Rectangular hyperbola
(B) Circle about the origin
(C) Straight line through the origin
(D) Straight line parallel to the speed axis.
View Answer / Hide AnswerANSWER: Rectangular hyperbola
(12) In smooth cylindrical conductors in air at NTP disruptive corona begins, if electric field intensity at the conductor surface goes up to
(A) 21.1 Kv (peak)/cm
(B) 21.1 Kv (rms)/cm
(C) 21.1 Kv (average)/cm
(D) 21.1 Kv (rms)/m
View Answer / Hide Answer(13) What is the reflection coefficient for the transmission line at point P?
(A) ∞
(B) -1
(C) 1
(D) 0
View Answer / Hide Answer(14) At an angle of 30° with the vertical a radiowave is incident on a layer of ionosphere. What will be the maximum usable frequency if critical frequency is 1.2 MHz?
(A) 2.646 MHz
(B) 0.356 MHz
(C) 1.386 MHz
(D) 1.843 MHz
View Answer / Hide Answer(15) The rotor circuit of a 6-pole 50 Hz induction motor makes 30 oscillations in one minute considering a center zero ammeter connected to a rotor circuit. The speed of the rotor is
(A) 990
(B) 1000
(C) 500
(D) 1500
View Answer / Hide Answer(16) Internal resistance of a 100μA ammeter is 100 ohm. What should be the value of shunt resistance required in order to extend its range to measure 500μA?
(A) 22ohm
(B) 25ohm
(C) 20ohm
(D) 50ohm
View Answer / Hide Answer(17) For the 2-phase servomotor X / R ratio is (where X is rotor reactance and R is rotor resistance)
(A) Less than or greater than that of a normal induction motor
(B) Greater than that of a normal induction motor
(C) Equal to that of a normal induction motor
(D) Less than that of a normal induction motor
View Answer / Hide AnswerANSWER: Less than that of a normal induction motor
(18) Let firing angle in a 3-phase semi-converter be = 60°. The duration of conduction of each thyristor and diode would be respectively
(A) 120° and 60°
(B) 120° and 120°
(C) 60° and 120°
(D) 60° and 60°
View Answer / Hide Answer(19) Consider the circuit shown below. This circuit is equivalent to a load of
(A) 1/4 ohms
(B) 3/2 ohms
(C) 8/3 ohms
(D) 3/8 ohms
View Answer / Hide Answer(20) The admittance parameters of a two port network shown in the figure are Y11 = 8 mho, Y12 = Y21 = -6 mho, Y22 = 6 mho. What will be the respective values of YA, YB and YC in the units
of mho?
(A) 2, 5 and 8
(B) 2, 0 and 6
(C) 2, 6 and 0
(D) 2, 1 and 4
View Answer / Hide Answer(21) To give rated output of 1500rpm a 240V dc series motor takes 40 A current. Its resistance is 0.3 ohms. To obtain rated torque at 1000rpm, the value of resistance, which must be added,
is
(A) 5 ohms
(B) 2.3 ohms
(C) 1.9 ohms
(D) 6.9 ohms
View Answer / Hide Answer(22) The starting address of an 8085 microprocessor based system that uses a 4K x 8 bit RAM is AA00 H. In this RAM the address of the last byte is
(A) BA00 H
(B) 1000 H
(C) B9FF H
(D) 0FFF H
View Answer / Hide Answer(23) Consider a JFET whose gm is 1 mA/V and Cgs + Cgd + Cgss = 5 pF. Symbols have their usual meaning. Ft of the JFET is nearly equal to
(A) 1 MHz
(B) 10 MHz
(C) 20 MHz
(D) 30 MHz
View Answer / Hide Answer For Questions 24 and 25 refer to the data given below:
X = 20nc and Y = 10nc are the two point charges separated from each other at a distance of 25 cm in free space.
(24) A point D is 15 cm away from point X and 20 cm away from point Y. The electric field at point D is
(A) 8.31 kV/m
(B) 9.2 kV/m
(C) 3.2 kV/m
(D) 4.5 kV/m
View Answer / Hide Answer(25) The angle θ is
(A) 15.7°
(B) 9.8°
(C) 21.9°
(D) 11.2°
View Answer / Hide Answer
