** ****MPSC Lecturer, Electrical Engineering, Government Polytechnic, Maharashtra Polytechnic Teachers Service, Gr.A Question paper 2013**

**A two port network has transmission parameters, the input impedance of the network at port 1 will be:**

** **(1) AD/BC

(2) A/C

(3) AB/DC

(4) D/C

**The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be:**

(1) 1500 rpm

(2) 900 rpm

(3) 750 rpm

(4) 375 rpm

**A generating station has maximum demand of 25 MW, load factor of 60%, a plant capacity factor of 50% and plant use factor of 72%. What is the reserve capacity of plant if the plant, while running as per the schedule, was fully loaded?**

(1) 10 MW

(2) 15 MW

(3) 2 MW

(4) 5 MW

**The slew rate of an op-amp is 0.5 V/ILS. The maximum frequency of a sinusoidal input of 2 V rms that can be handled without excessive distortion is:**

(1) 3 kHz

(2) 30 kHz

(3) 200 kHz

(4) 2 MHz

**A shunt generator produces 450 amp at 230 V. The resistances of the shunt fields and armature are 50 ohm and 0.025 ohm respectively. The armature voltage drop will be:**

(1) 11.39 V

(2) 22.7 V

(3) 31.6 V

(4) 38.4 V

**Sensor outputs destined for a digital computer system must first be processed by:**

(1) D/A

(2) A/D

(3) MPU

(4) PLD

**A resistance of 12 ohms and inductance of 0.15 H and a capacitance of 1.0 microfarad are connected in series across a 100 V, 50 Hz supply. The power factor of the circuit will be:**

(1) Unity

(2) Zero

(3) Leading

(4) Lagging

**A switch is connected in series with RL series circuit, a switch is closed at t = 0. The circuit was initially relaxed. Which of the following sources of v (t) will produce maximum current at t=O+?**

(1) Unit step

(2) Unit ramp

(3) Unit impulse

(4) Exponential

**If the vector field***F = (x + 2y +az)i + (- 2x – 3y – z)j + (4x – y + 2z)k*is irrotational then the value of a is :

(1) – 4

(2) 3

(3) 3

(4) 4

**An open loop system represented by the transfer function G(s) =(s -1)/(s +2) (s +3) is:**

(1) Stable and of the minimum phase type

(2) Stable and of the non-minimum phase type

(3) Unstable and of the minimum phase type

(4) Unstable and of the non-minimum phase type

**The maximum value of mutual inductance of two inductively coupled coils with self inductance L**_{1}=49 H and L2 =81 H is:

(1) 130 mH

(2) 63 mH

(3) 32 mH

(4) 2658 mH

**In an alternator, if the winding is short pitched by 50 electrical degrees, its pitch factor will be:**

(1) 1.6

(2) 0.866

(3) 0.78

(4) 0.50

**If the secondary of a 1: 10 step up transformer is connected to the primary of a 1 : 5 step up transformer, the total transformation ratio will be :**

(1) 2500

(2) 30

(3) 15

(4) 50

**The discrete time system described by***y (n) =x (n*is:^{2})

(1) causal, linear and time variant

(2) causal, linear and time invariant

(3) non-causal, linear and time invariant

(4) non-causal, linear and time variant

**In 220 k\7 system, the inductance and capacitance up to the location of circuit breaker is 0.0254 H and 0.025 microfarad respectively. The resistance of 600 ohm is connected across the contacts ot the circuit breaker, the natural frequency of oscillation will be:**

(1) 4.47 kHz

(2) 6.31 kHz

(3) 3.41 kHz

(4) 10 kHz

**A DC generator running at 1600 rpm gives 240 V dc. If the speed is dropped to 1400 rpm, without change in flux, the new e.m.f. will be:**

(1) 270 V

(2) 240 V

(3) 237 V

(4) 210 V

**‘The trigonomehic Fourier series of a periodic time function have:**

(1) sine term

(2) cosine term

(3) DC terms and (1) and (2)

(4) both (1) and (2)

**A two port network is defined by the relations I**_{1}= 2V_{1}+V_{2 }and I_{2}= 2V_{1}+3V_{2}, then Z_{12}is:

(1) -7 ohm

(2) — 5 oh127

(3) – 0.5 ohm

(4) None of these

**A 3-phase fully controlled bridge converter with freewheeling diode 1s fed from 400 V, 50 Hz AC source and is operating at a firing angle of 60c. The load current is assumed constant at 10 A due to high load inductance. The Input Displacement Factor (IDF) and the Input Power Factor (IFF) of the converter will be:**

(1) IDF = 0.567; IPF =: 0.828

(2) IDF = 0.867; IPF = 0.552

(3) IUI: – 0.5; 1PF = 0.478

(4) IDF = 0.5; IFF = 0.318

**If f (z) = r**^{3}cos 30 + ir^{3}sin k0 is analytic, then k is equal to:

(1) 1

(2) 3

(3) – 3

(4) 2

**Two amplifiers, one having voltage gain of 40 and the other of 20 are coupled with negligible loading. The approximate gain of two-stage amplifier will be:**

(1) 20

(2) 40

(3) 60

(4) 800

**A D.C. Chopper has a TON (time to go on) of 1 msec and its frequency is 500 Hz. What will be its duty cycle?**

(1) 100%

(2) 50%

(3) 25%

(4) information is insufficient

**An astable multivibrator requires__________.**

(1) balanced time constants

(2) a pair of matched transistors

(3) no input signal

(4) dual J-K flip-flops

**A 3-phase breaker is rated at 2000 MVA, 33 kV its making current will be:**

(1) 35000 A

(2) 49000 A

(3) 70000 A

(4) 89000 A

**In any transmission line, AD – BC =**

(1) -1

(2) + 1

(3) A*B

(4) C*D

**The open loop transfer function G(s) of a unity feedback control system is given as,***G(s) = [K*(s + 2/3)/s2(s + 2)].*From the root locus, it can be inferred that when K tends to positive infinity:

(1) three roots with nearly equal real parts exist on the left half of the s-plane

(2) one real root is found on the right half of the s – plane

(3) the root loci cross the jo axis for a finite value of K; Kg3

(4) three real roots are fluid on the right half of the s – plane

**For an SCR, dv/dt protection is achieved through the use of:**

(1) R in series with SCR

(2) L in series with SCR

(3) L in series with SCR

(4) RLC in series with SCR

**When the reverse voltage across a p-n junction is gradually decreased, the depletion region:**

(1) does not change in width

(2) initially increases up to a certain width and then decreases

(3) continuously increases in width

(4) continuously decreases in width

**The latching current of SCR is 18 mA. Its holding current will be:**

(1) 16 mA

(2) 18 mA

(3) 54 mA

(4) None of these

**A multiplexer is a logic circuit that:**

(1) accepts one input and gives several outputs

(2) accepts many inputs and gives many outputs

(3) accepts many inputs and gives one output

(4) accepts one input and gives one output

**A generating station has the maximum demand of 75 MW, a load factor of 60%, find the average demand.**

(1) 45 MW

(2) 41 MW

(3) 0.41 MW

(4) 125 MW

**For the successful parallel operation of two single phase transformers,. the most essential condition is that their :**

(1) percentage impedances are equal

(2) turns ratio are exactly equal

(3) KVA ratings are equal

(4) polarities are properly connected

**In 3-phase controlled bridge rectifier, with an increase of overlap angle, the output DC voltage :**

(1) decreases

(2) does not change

(3) increases

(4) depends upon load inductance

**A power system network with a capacity of 100 MVA has a source impedance at 10% at a point. The fault MVA at that point is :**

(1) 10 MVA

(2) 30 MVA

(3) 3000 MVA

(4) 1000 MVA

**A 3 ph delta/star transformer is supplied at 6000 V on the delta connected side. The terminal voltage on secondary side when supplying full load at 0.8 lagging p.f. is 415. The equivalent resistance and reactance drop for the transformer are 7% and 5% respectively. The turn’s ratio of the transformer is :**

(1) 14

(2) 12

(3) 42

(4) None of these

**For a three phase induction motor input power on no load is W, = 600 watts and windage and friction losses Wf = 183 watts. The stator copper losses will be equal to :**

(1) 783

(2) 600

(3) 183

(4) 517

**Two 11 kV, 20 MVA, three phase star connected generator operated in parallel the positive, negative and zero sequence reactance of each j36, 130, j20 p u. The star point of generdtor is isolated and that of the other is earthed to 2 ohm resistor. The single line to ground fault occurs at the terminals of one generator. The fault current will be :**

(1) 2.5 p.u

(2) 2.66 p.u

(3) 1.24 p.u

(4) 2.95 p.u

**Which mode of operation is being used when a 555 timer chip has two external resistors and an external capacitor?**

(1) monostable

(3) Schmitt triggering

(2) pulse stretching

(4) astable

**An n-channel JFET has pinch-off voltage V**_{p}= -4 volts. Liven VGS = – 1 V, the minimum V_{DS }for the device to operate in the pinch-off region will be :

(1) +1 v

(2) +3 v

(3) +4 v

(4) +5 v

**In a thyristor D.C. chopper, which type of commutation results in best performance ?**

(1) Voltage commutation

(2) Current commutation

(3) Load cornmutatlon

(4) Supply commutation

**Steady state stability of a power system is the ability of power system to :**

(1) maintain voltage at rated voltage level

(2) maintain frequency exactly at 50 Hz

(3) maintain a spinning reserve margin at all times

(4) maintain synchronism

**The per unit impedance of a synchronous machine is 0.242. If base voltage is increased by 1.1 times, the per unit value will be :**

(1) 0.269

(2) 0.242

(3) 0.250

(4) 0.200

**System described by***y(n) =x(n)+ x(n – 2)*is .

(1) Causal

(2) Non-causal

(3) Arbitrary

(4) Both (1) and (3)

**Coefficient of correlation between the variables s and i/ is 0.8 and their covariance is 20, the variance of x is 16. Standard Deviation of y is :**

(1) 0.269

(2) 0.242

(3) 0.250

(4) 0.200

**System described by y(n) =x(n)+ x(n- 2) is .**

(I) Causal

(2) Non-causal

(3) Arbitrary

(4) Both (1) and (3)

**Coefficient of correlation between the variables s and i/ is 0.8 and their covariance is 20, the variancc of x is 16. Standard Deviation of y is :**

(1) 6.75

(2) 8.25

(3) 7.5

(4) 6.25

**Digital voltmeter measures :**

(1) peak value

(2) rms value

(3) peak to peak value

(4) average value

**A DC motor develop$ a torque of 140 N-m at 1400 rpm. If the motor now runs at 1000 rpm, the torque developed****will be:**

(1) 1400 N-m

(2) 1000 N-m

(3) 140 N-m

(4) 410 N-m

**A three phase induction motor has a copper loss of 800 watts and slip of 4%. The rotor input must be :**

(1) 8 kW

(2) 4 kW

(3) 0.2 kW

(4) 2 kW

**A 2 kVA transformer has iron loss of 150 watts and full load copper loss of 250 watts. The maximum efficiency of the transformer would occur when the total loss is :**

(1) 500 watts

(2) 300 watts

(3) 400 watts

(4) 275 watts

**the egivensystemoflinearequationx-4y+5z=-1,2x-y+3z=1,3x+2y+z=3has:**

(1) Unique solution

(2) No solution

(3) Infinitely many solutions

(4) n – r solution

**A single phase energy meter is operating on 230 V, 50 Hz, supply with a load of 20 amp. For two hours at UPF. The meter makes 1380 revolutions in that period. The meter onstant is :**

(1) 0.15 rev/kWh

(2) 105 rev/kWh

(3) 150 rev/kWh

(4) 1/150 rev/kWh

**Four identical alternators each rated for 20 MVA, 11 kV, having a sub transient reactance of 16% are working in parallel. The short circuit level at the bus bar is :**

(1) 500 MVA

(2) 400 MVA

(3) 125 MVA

(4) 80 MVA

**The corona loss on a particular system at 50 Hz i5 1 kW/ph/km. The corona loss on the same system with the supply frequency 25 Hz will be**

(1) 1 kW/ph/km

(2) 0.5 kW/ph/km

(3) 0.667 kW/ph/km

(4) 1.667 kW/ph/km

**Solution of equation y’ =x**^{2}+y^{2}for x=0.25 and x=0.5 given y(0)=1:

(1) 1.37 and 1.97

(2) 1.33 and 1.81

(3) 1 and 2

(4) 1.21 and 1.37