Thursday, 3 November 2016

AMCAT Electrical Engineering Core Paper


Let x = Ax + Bu, y = Cx be the state space equation of a system where x is the state vector, u is input and y is output. 



(1) What will be the transfer function of this system?

(A) 1 / s(s+2)
(B) (s+1) / s(s+2)
(C) s / (s+1)
(D) s / (s+2)

ANSWER: 1 / s(s+2)


(2) To make it a closed loop system a unity feedback is provided to the system described above, as shown in the figure.



What will be the steady state error in the output for a unit step input u (t)?

(A) 0
(B) 1
(C) ∞
(D) None of the above

ANSWER: 0

For questions 3 and 4 refer to the data given below:

k G(s) = k(s+2) ² / s² (s-1)

(3) For stable operation the range of K will be

(A) -1(B) 0(C) 1(D) 2

ANSWER: 0



(4) The imaginary axis crossover points is

(A) ± j1√2
(B) ± j√2
(C) ± j√5
(D) ± j2√2

ANSWER: ± j2√2


(5) Which one of the following statement is true for the set of equations given below?

a1 + 2 a2 + a3 + 4 a4 = 2

3 a1 + 6 a2 + 3 a3 + 12 a4 = 6

(A) There are no solutions
(B) There are multiple non-trivial solutions.
(C) There is a unique non-trivial solution
(D) Only the trivial solution a1 = a2 = a3 = a4 = 0 exists.

ANSWER: There are multiple non-trivial solutions.


(6) In channel1 and channel2 of an oscilloscope, two in-phase, 50Hz sinusoidal waveforms of unit amplitude are fed. Assume voltage scale, time scale and other settings are exactly same 

for both the channels. If the oscilloscope is operated in X-Y mode what will be observed?

(A) A straight line inclined at 45° with respect to x-axis
(B) A circle
(C) A parabola
(D) An ellipse

ANSWER: A straight line inclined at 45° with respect to x-axis


(7) Figure shows the periodic voltage waveform observed on an oscilloscope across the load. If a permanent magnet moving coil (PMMC) meter is connected across the same load then it will 

read



(A) 8V
(B) 4V
(C) 1V
(D) 10V

ANSWER: 4V


(8) R1 = R2 =120 are the two fixed resistances of a single element strain gauge bridge. The bridge has a variable resistance, which gives full deflection at 120ohms at zero strain and at 

120.6 ohms with a strain. What will be the value of strain in the beam if gauge factor of the strain gauge is 2?

(A) 0.0025
(B) 0.025
(C) 0.25
(D) 0.5

ANSWER: 0.0025


(9) Consider a 2 x 2 matrix whose trace is –2 and determinate is –35. The Eigen values are

(A) 2 and -4
(B) -4 and 6
(C) -1 and 2
(D) -7 and 5

ANSWER: -7 and 5


(10) The phase crossover frequency for the transfer function 

G(s)H(s) = 1/s(s+1)(s+0.5) is

(A) 1.5 rad/sec
(B) 0.707 rad/sec
(C) 1.7 rad/sec
(D) 0.6 rad/sec

ANSWER: 0.707 rad/sec


(11) Which one of the following statement is true for the circuit turn-off time of an SCR? 

(A) It is the time for which the SCR is reverse biased to reduce its current below the holding current.
(B) It is the time for which the SCR is reverse biased by the commutation circuit.
(C) It is the time taken by the SCR to turn off.
(D) It is the time required for the SCR current to become zero.

ANSWER: It is the time for which the SCR is reverse biased by the commutation circuit.


(12) RST instruction is an 8085 microprocessor system will cause an interrupt only if

(A) Interrupts are enabled by an EI instruction
(B) An interrupt service routine is not executed.
(C) Interrupt mask bit is made 0
(D) None of the above

ANSWER: Interrupts are enabled by an EI instruction


(13) A transmission line has load impedance equal to characteristic impedance. The values of standing wave ratio and reflection coefficient are respectively

(A) 1 and 1
(B) 0 and 0
(C) 1 and 0
(D) 0 and 1

ANSWER: 1 and 0


(14) Consider a lossless transmission line whose surge impedance loading (SIL) is 2280 MW. It is provided with a uniformly distributed series capacitive compensation of 30%. SIL of the 

compensated transmission line will be

(A) 2000 MW
(B) 2725 MW
(C) 3000 MW
(D) 3725 MW

ANSWER: 2725 MW


For Questions 15 and 16 refer to the data given below:

200V is applied to the armature of a separately excited DC motor that runs at a speed of 1500 rpm under no-load. The field voltage is maintained at its rated value. The rotational 

loss and armature reaction are neglected. The figure shows that when the torque delivered by the motor is 5Nm, the speed of the dc motor is 1400rpm.



(15) What is the armature resistance of the motor?

(A) 1.5Ω
(B) 4.5Ω
(C) 5.4Ω
(D) 3.4Ω

ANSWER: 3.4Ω


(16) When the torque to be delivered by the motor is 2.5Nm at 1400 rpm how much armature voltage should be applied?

(A) 184.5 V
(B) 120.6 V
(C) 150.1 V
(D) 193.3 V

ANSWER: 193.3 V


(17) The race around condition in the circuit given below



(A) Occurs when CLK is 1 and input x and y are 0
(B) Occurs when CLK is 1 and input x and y are 1 
(C) Occurs when CLK is 0
(D) Does not occur

ANSWER: Does not occur


(18) Match the following and select the correct option.
List I List II
Type of transmission line Type of distance relay preferred

i) Short line x) Ohm Relay
ii) Medium line y) Reactance Relay
iii) Long line z) MHO Relay

i) ii) iii)

(A) x z y
(B) x y z
(C) y x z
(D) z y x

ANSWER: x y z
(19) In the interval [1,9] the maximum value of f(x) = x³ - 9x² + 24x +5 is

(A) 41
(B) 28
(C) 36
(D) 16

ANSWER: 41


(20) Consider the circuit shown below. What will be the voltage Vxy if we assume ideal elements in the circuit?



(A) 0V
(B) 1V
(C) -3V
(D) 3V

ANSWER: -3V


(21) Consider an image that uses 12 x 512 picture elements. What will be the maximum entropy of the image when each of the picture elements can take any of the 8 distinguishable intensity 

levels?

(A) 209165 bits
(B) 765439 bits
(C) 694 bits
(D) 144 bits

ANSWER: 144 bits


(22) The open loop system whose transfer function is given by 

G(s) = (s–1)/ (s+2)(s+3) is

(A) Unstable and of the non-minimum phase type
(B) Stable and of the non-minimum phase type
(C) Unstable and of the minimum phase type
(D) Stable and of the minimum phase type

ANSWER: Stable and of the non-minimum phase type


(23) What will be the product of two matrices A and adj. A?

(A) Scalar matrix
(B) Unit matrix
(C) Zero matrix
(D) Matrix A itself

ANSWER: Scalar matrix


(24) In India picture and speech signals in commercial TV transmission are modulated respectively as

(A) VSB and FM
(B) FM and SSB
(C) SSB and VSB
(D) VSB and VSB

ANSWER: VSB and FM


(25) Consider a 3-phase, star connected 15Kw, 4-pole, 230V, 50Hz induction motor. At rated conditions the locked rotor current is 50A. Losses and magnetizing current are negligible. When 

the motor is connected to a 236V, 57Hz supply, the approximate locked rotor line current drawn is

(A) 50.2 A 
(B) 34.8 A
(C) 45.0 A
(D) 25.9 A

ANSWER: 45.0 A

Set 2

(1) The width of the diode current pulse in a 2-pulse bridge converter with freewheeling diode is (α is firing angle)

(A) 2α
(B) α/2
(C) π - α
(D) π
ANSWER: 2α


(2) Consider a 3-phase induction motor whose rotor power output is 15Kw and corresponding slip is 4%. The rotor copper loss will be

(A) 825W
(B) 725W
(C) 625W
(D) 225W
ANSWER: 625W


(3) Four alternators are working in parallel. Rating of each alternator is 5MVA, 11KV with 20% reactance. The short circuit level at bus bars is 

(A) 0
(B) 25MVA
(C) 100MVA
(D) 6.25MVA
ANSWER: 6.25MVA


(4) Which one of the following statement is true? The compensating winding in a dc machine is located 

(A) On commutating poles for improving the commutation
(B) On pole shoes to avoid the sparking at the brushes
(C) In armature slots for compensating of the armature reaction
(D) On pole shoes for avoiding the flashover at the commutator surface
ANSWER: On pole shoes for avoiding the flashover at the commutator surface


(5) The number of rotor teeth for a 1.8 step, 4-phase stepper motor that has a total of 40 teeth on 8 poles of stator will be

(A) 100
(B) 50
(C) 80
(D) 40
ANSWER: 50


(6) The magnitude of the voltage developed across the capacitor in a series RLC circuit at resonance 

(A) Can be greater than the input voltage, and is in phase with the input voltage
(B) Can be greater than the input voltage, however it is 90° out of phase with the input voltage
(C) Is always zero
(D) Can never be greater than the input voltage
ANSWER: Can be greater than the input voltage, however it is 90° out of phase with the input voltage


(7) ___________is the slowest analog to digital converter

(A) Integrating type
(B) Flash type
(C) Counting type
(D) Successive approximation type
ANSWER: Integrating type


(8) With B open the resistance between Y and G is 6Ω, with Y open the resistance between G and B is 11Ω and with G open the resistance between B and Y is 9Ω. The respective 

values of Ry, Rg and Rb are



(A) 5 Ω, 4 Ω, 6 Ω
(B) 4 Ω, 8 Ω, 7 Ω
(C) 1 Ω, 6 Ω, 5 Ω
(D) 2 Ω, 4 Ω, 7 Ω
ANSWER: 2 Ω, 4 Ω, 7 Ω


(9) MVI X, 10H
MVI Y, 10H
BACK: NOP
ADD Y
RLC
JNC BACK
HLT

The above program is executed in an Intel 8085 processor. The operation NOP is executed __________times.

(A) 1
(B) 3
(C) 5
(D) 2
ANSWER: 3


(10) Consider the figure given below. The source voltage is Vm sin (ωt) and ω=314rad/s. The forward resistance of diode is 5Ω and the remaining parameters are same as that 

of an ideal diode. The dc component of source current is



(A) 2Vm/100π
(B) 2Vm/50π
(C) Vm/50π
(D) Vm/100π
ANSWER: Vm/50π


(11) D flip-flop shown in the figure is triggered at rising edge. The frequency of clock signal is 10KHz. The signal available at Q will have the frequency of



(A) 5KHz
(B) 10KHz
(C) 20KHz
(D) 1KHz
ANSWER: 5KHz

(12) Consider an ac machine with 60° phase spread. For this ac machine a 4-pole, 3-phase, double layer winding is housed in a 36-slot stator. Coil span is 7 slot pitches. Number of 

slots in which top and bottom layers belong to different phases is

(A) 5
(B) 12
(C) 10
(D) 18
ANSWER: 12


(13) Let L = 10 +3θ - θ²/4 μH be the inductance of a certain moving iron ammeter, where θ` is the defection in radians from the zero position. The control 

spring torque is 25 x 10-6 Nm/radian. When the meter carries a current of 5A the deflection of the pointer in radian is

(A) 1.0
(B) 2.0
(C) 1.8
(D) 1.2
ANSWER: 1.2


(14) To a synchronous generator a hydraulic turbine of 250rpm speed is connected. The number of poles required in a generator, in order to produce power at 50 Hz is

(A) 20
(B) 10
(C) 24
(D) 12
ANSWER: 24


(15) The number of roots in the left half of s plane for the equation, s³ - 4s² + s + 6 = 0 will be

(A) 1
(B) 2
(C) 3
(D) 4
ANSWER: 2


(16) The pressure in the working fluid cycle, in thermal power plants is developed by

(A) Feed water pump
(B) Condenser
(C) Turbine
(D) Super heater
ANSWER: Feed water pump


(17) For a power MOSFET, the conduction loss versus device current characteristic is best approximated by 

(A) An exponentially decaying function
(B) A rectangular hyperbola
(C) A straight line
(D) A parabola
ANSWER: A parabola


(18) Consider a three-phase system supplying a balanced load. To measure the total power two wattmeters are connected which reads 10.5Kw and –2.5Kw respectively. The total power and the 

power factor respectively are

(A) 8.0Kw, 0.334
(B) 8.0Kw, 0.553
(C) 10Kw, 0.7
(D) 10Kw, 0.45
ANSWER: 8.0Kw, 0.334


(19) Consider the figure given below. As seen at the terminal P-Q the Thevenin’s equivalent pair (voltage, impedance) is given by



(A) 2v, 6ohm
(B) 2v, 5ohm
(C) 4v, 20ohm
(D) 4v, 5ohm
ANSWER: 2v, 5ohm


(20) In a Wheatstone bridge R1 and R4 are the opposite arms and R3 and R2 are opposite arms. If a source voltage is applied across R1 and R3, which one of the following is correct under 

balanced conditions? 

(A) R1 = R2 + R3 + R4
(B) R1 = R3 R4/R2
(C) R1 = R2 R3/R4
(D) R1 = R2 R4/R3
ANSWER: R1 = R2 R3/R4


(21) Which one of the following statement is incorrect for the Gauss seidel load flow method?

(A) Initial guess for voltages is essential for convergence
(B) Choice of slack bus affects convergence
(C) Unreliable convergence
(D) Slow convergence
ANSWER: Unreliable convergence


(22) The zero speed regulation at full load without any controller can be provided with

(A) Differential compound dc motor
(B) Cumulative compound dc motor
(C) Series dc motor
(D) Shunt dc motor
ANSWER: Differential compound dc motor


For Questions 23 and 24 refer to the data given below:




R1 and R2 are the two types of rotate right instructions that are available in a microprocessor. Reg is an 8-bit register and C is the carry bit. Rotate left instructions L1 and L2 are 

similar except that C now links the most significant bit of Reg instead of the least significant bit.

(23) Let Reg contains 2’s complement number 11010110. What will be the answer if this number is divided by 2?

(A) 00011010
(B) 11101011
(C) 10001000
(D) 11010101
ANSWER: 11101011


(24) Which set of operation can be used to correctly perform such a division? 

(A) L2, R2, R1
(B) R2, L1, R1
(C) R1, L2, R2
(D) L2, R1, R2
ANSWER: L2, R2, R1


(25) What will be the result if distributed winding and short chording are employed in AC machines?

(A) It will increase emf and reduce harmonics
(B) It will reduce emf and increase harmonics
(C) It will reduce both emf and harmonics
(D) It will increase both emf and harmonics
ANSWER: It will reduce both emf and harmonics

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