SAIL SAMPLE PAPER ELECTRICAL ENGG [Q-1] Silicon based rectifiers are preferred than germanium based rectifiers because (a) Si is available easily compared to Ge (b) Only Si has a stable off state (c) Ge is very temperature sensitive (d) Si only has the characteristics α1 + α2 < 1 at low collector currents and reaches 1 at high currents Which of the above statements are true? Options: 1. A, B, D 2. B, D 3. B Only 4. D Only 5. None of the above options Answer: 2 [Q-2] In a triac, (a) The triggering pulse to main terminal 1 should be of the same polarity as the anode potential between MT1 and MT2 (b) The triggering pulse should be of opposite polarity to that of anode potential (c) When the triggering pulse is positive and anode is positive, it is operating in the first quadrant (d) When the triggering pulse is negative and anode is negative its sensitivity is highest. Which of the above statements are true? Options: 1. A, D 2. A, C 3. C, D 4. A, C, D 5. None of the above options Answer: 4 [Q-3] In a single phase full wave SCR circuit with R, L load (a) Power is delivered to the source for firing angle of less than 90° (b) The scr changes from inverter to converter at α = 90° (c) The negative dc voltage is maximum at α = 180°
(d) To turn off the scr, the maximum delay angle must be less than 180° Which of the above statements are true? Options: 1. C, D 2. C Only 3. D Only 4. A , B 5. None of the above options Answer: 1 [Q-4] While comparing triac and scr, (a) Both are unidirectional devices (b) Triac requires more current for turn on than scr at a particular voltages (c) A triac has less time for turn off than SCR (d) Both are available with comparable voltage and current ratings Which of the above statements are true? Options: 1. A, C 2. B, C 3. A, B 4. D Only 5. None of the above options Answer: 2 [Q-5] Which of the following statements are true (a) If the SCR, even with proper gate excitation and anode-cathode voltage does not conduct for a particular load resistance, then it would be necessary to decrease the load resistance to turn ON the SCR (b) The SCR would be turned OFF by voltage reversal of the applied anodecathode ac supply of frequencies up to 30kHz (c) If the gate current of the SCR is increased, then the forward breakdown voltage will decrease Options 1. A, B, C 2. B, C 3. A , C 4. A, B 5. None of the above options
Answer: 3 [Q-6] Which of the following statements are true When gate triggering is employed, a SCR can withstand higher values of di/dt, if the 1. Gate current is increased 2. Rate of rise of gate current is increased 3. Gate current is increased 4. Rate of rise of gate current is decreased OPTIONS: (a) 3, 4 (b) 1, 4 (c) 2, 3 (d) 1, 2 (e) None of the above options Answer: A [Q-7] In a SCR based converter, the free wheeling diode is used to (a) Add to the conduction current of thyristors (b) Oppose the SCR conduction (c) Conduct current during the OFF period of the SCR (d) Protect the SCR by providing a shunt path Answer: C [8] For a fault at terminals of the synchronous generator the fault current is max for a (a) 3 phase fault (b) 3 phase to ground fault (c) Line to ground fault (d) Line to line fault Answer: A
will be (a) 100MJ (b) 400MJ (c) 800MJ (d) 12.5MJ Answer: B
[9] Reactance relay is normally preferred for protection against (a) Earth faults (b) Phase faults (c) Open circuit faults (d) None of the above Answer: B
[14] A three-phase, 33kV oil circuit breaker is rated 1200A, 2000MVA, 3s. The symmetrical breaking current is A. 1200A B. 3600A C. 35kA D. 104.8Ka Ans:C
[10] A 100 MVA, 11kV, 3 phase, 50Hz, 8 pole synchronous generator has a inertia constant H = 4 seconds. The stored in the rotor of the generator at synchronous speed
[11] The use of high speed circuit breakers (a) Reduces the short circuit current (b) Improves system stability (c) Decreases system stability (d) Increases the short circuit current Answer: B [12] Bundled conductors are employed to improve the (a) Appearance of the transmission line (b) Mechanical stability of the line (c) Current carrying capability of the line (d) Corona performance of the line Answer: D [13] For enhancing the power transmission in a long EHV transmission line, the most preferred method is to connect a A. Series inductive compensator in the line B. Shunt inductive compensator at the receiving end C. Series capacitive compensator in the line D. Shunt capacitive compensator at the sending end Ans:C
[15] In a transformer, zero voltage regulation at full load is (a) Not possible
(b) Possible at unity Power factor load (c) Possible at leading Power factor load (d) Possible at lagging Power factor load Ans:C [16] The DC motor, which can provide zero speed regulation at full load without any controller is (a) Series (b) Shunt (c) Cumulative Compound (d) Differential Compound Ans:B [17] In 8 - pole wave connected motor armature, the number of parallel paths are (a) 8 (b) 4 (c) 2 (d) 1 Ans: C [18] In a transformer the voltage regulation will be zero when it operates at (a) Unity p.f. (b) Leading p.f. (c) Lagging p.f. (d) Zero p.f. leading. Answer: B [19] In a stepper motor the angular displacement (a) Can be precisely controlled. (b) It cannot be readily interfaced with micro computer based controller. (c) The angular displacement cannot be precisely controlled. (d) It cannot be used for positioning of work tables and tools in NC machines. Answer: A [20] The power factor of a squirrel cage induction motor is (a) Low at light load only. (b) Low at heavy load only.
(c) Low at light and heavy load both. (d) Low at rated load only. Answer: A [21] The generation voltage in India is usually (a) Between 11 KV and 33 KV. (b) Between 132 KV and 400 KV. (c) Between 400 KV and 700 KV. (d) None of the above. Answer: A [22] When a synchronous motor is running at synchronous speed, the damper winding produces (a) Damping torque. (b) Eddy current torque. (c) Torque aiding the developed torque. (d) No torque. Answer: D [23] If a transformer primary is energised from a square wave voltage source, its output voltage will be (a) A square wave. (b) A sine wave. (c) A triangular wave. (d) A pulse wave. Answer: A [24] A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will (a) Come to stop. (b) Continue to run at synchronous speed. (c) Continue to run at a speed slightly more than the synchronous speed. (d) Continue to run at a speed slightly less than the synchronous speed. Answer: B [25] The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about (a) 50 Hz. (b) 20 Hz.
(c) 2 Hz. (d) Zero. Answer: C [26] The speed of a dc motor can be controlled by varying (a) Its flux per pole (b) Resistance of armature circuit (c) Applied voltage (d) All of the above Answer: D [27] Regarding Ward-Leonard system of speed control which statement is false? (a) It is usually used where wide and very sensitive speed control is required (b) It is used for motors having ratings from 750kW to 4000kW (c) Capital outlay involved in the system is right since it uses two extra machines (d) It gives a speed range of 10:1 but in one direction only (e) It has low overall efficiency especially at light loads Answer: D [28] A stepper motor is (a) A dc motor. (b) A single-phase ac motor. (c) A multi-phase motor. (d) A two phase motor. Answer: D Stepper motor works on 1-phase-ON or 2phase –ON modes of operation [29] A motor which can conveniently be operated at lagging as well as leading power factors is the (a) Squirrel cage induction motor. (b) Wound rotor induction motor. (c) Synchronous motor. (d) DC shunt motor. Answer: C [30] The d.c. series motor should always be started with load because
(a) At no load, it will rotate at dangerously high speed. (b) It will fail to start. (c) It will not develop high starting torque. (d) All are true. Answer: A [31] The ‘sheath’ is used in cable to (a) Provide strength to the cable. (b) Provide proper insulation. (c) Prevent the moisture from entering the cable. (d) Avoid chances of rust on strands. Answer: A The sheath in underground cable is provided to give mechanical strength. [32] The drive motor used in a mixer-grinder is a (a) DC motor. (b) Induction motor. (c) Synchronous motor. (d) Universal motor. Answer: D The universal motor is suitable for AC & DC both supply systems. [33] A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is (a) 1500 r.p.m. (b) 1425 r.p.m. (c) 25 r.p.m. (d) 75 r.p.m. Answer: D NS = 120f /P = 120 x 50 /4 =1500rpm N = NS ( 1-s) = 1500 (1-0.05) = 1425 Relative speed = 1500 – 1425 = 75 rpm [34] The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage
will be (a) 3.6 V. (b) 2.5 V. (c) 3.0 V. (d) 6.0 V. Answer: C [35] The current from the stator of an alternator is taken out to the external load circuit through (a) Slip rings. (b) Commutator segments. (c) Solid connections. (d) Carbon brushes. Answer: C [36] In a 3 – phase induction motor the maximum torque (a) Is proportional to rotor resistance r2 . (b) Does not depend on r2 . (c) Is proportional to square root of r2 . (d) Is proportional to square of r2 . Answer: B [37] In a d.c. machine, the armature mmf is (a) Stationary w.r.t. armature. (b) Rotating w.r.t. field. (c) Stationary w.r.t. field. (d) Rotating w.r.t. brushes. Answer: C [38]The size of the feeder is determined primarily by (a) The current it is required to carry. (b) The percent variation of voltage in the feeder. (c) The voltage across the feeder. (d) The distance of transmission. Answer: A [39] The emf induced in the primary of a transformer (a) Is in phase with the flux. (b) Lags behind the flux by 90 degree. (c) Leads the flux by 90 degree. (d) Is in phase opposition to that of flux.
Answer: C [40] The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (a) DC machine. (b) 3 phase induction machine. (c) Synchronous machine. (d) Single phase induction machine. Answer: all options are correct [41] As the voltage of transmission increases, the volume of conductor (a) Increases. (b) Does not change. (c) Decreases. (d) Increases proportionately. Answer: C Due to skin effect [42] In a 3-phase synchronous motor (a) The speed of stator MMF is always more than that of rotor MMF. (b) The speed of stator MMF is always less than that of rotor MMF. (c) The speed of stator MMF is synchronous speed while that of rotor MMF is zero. (d) Rotor and stator MMF are stationary with respect to each other. Answer: D Motor is magnetically locked into position with stator, the rotor poles are engaged with stator poles and both run synchronously in same direction. [43] An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging case. If it is required to deliver rated current at rated voltage and 0.8 powerfactor leading, the required excitation will be (a) Less. (b) More. (c) More or less. (d) The same.
Answer: B Over excitation gives leading power factor and under excitation gives lagging p.f . [44] Out of the following methods of heating the one which is independent of supply frequency is (a) Electric arc heating (b) Induction heating (c) Electric resistance heating (d) Dielectric heating Answer: C [45] In a capacitor start single-phase induction motor, the capacitor is connected (a) In series with main winding. (b) In series with auxiliary winding. (c) In series with both the windings. (d) In parallel with auxiliary winding. Answer: B To make single phase motor self start. We split the phases at 90 degree. Hence, motor behaves like a two phase motor. [46] A synchro has (a) A 3-phase winding on rotor and a singlephase winding on stator. (b) A 3-phase winding on stator and a commutator winding on rotor. (c) A 3-phase winding on stator and a singlephase winding on rotor. (d) A single-phase winding on stator and a commutator winding on rotor. Answer: C The basic synchro unit called a synchro transmitter. It’s construction similar to that of a Three phase alternator. [47] A ceiling fan uses (a) Split-phase motor. (b) Capacitor start and capacitor run motor. (c) Universal motor. (d) Capacitor start motor. Answer: D
To give starting torque and to maintain speed. [48] A hysteresis motor (a) Is not a self-starting motor. (b) Is a constant speed motor. (c) Needs dc excitation. (d) Can not be run in reverse speed. Answer: B [49] The most suitable servomotor for low power applications is (a) A dc series motor. (b) A dc shunt motor. (c) An ac two-phase induction motor. (d) An ac series motor. Answer: B [50] The size of a conductor used in power cables depends on the (a) Operating voltage. (b) Power factor. (c) Current to be carried. (d) Type of insulation used. Answer: C [51] A rectifier type instrument is connected to 100VDC and is operated in the DC measuring module reads (a) 111V (b) 90V (c) 50V (d) 100V Ans: A [52] A permanent magnet moving coil ammeter has a coil resistance of 99ohm and Full Scale Deflection(FSD) current of 0.1mA. Shunt resistance is 1 ohm. Current through the meter at 0.5 F.S.D is (a) 0.007mA (b) 0.05mA (c) 0.023mA (d) 0.1mA
Ans: B
Ans: B
[53] One single phase wattmeter operating on 230V and 5A for 5 hours makes 1940 revolutions. Meter constant in revolutions is 400. What is the power factor of the land? (a) 1 (b) 0.84 (c) 0.73 (d) 0.65
[58] A spring controlled indicating instrument has a deflection of 90deg for maximum current I. The corresponding deflection for a gravity controlled instrument is (a) 90° (b) 120° (c) 30° (d) 0° Ans: C
[54] For power measurement of three phase circuit by two wattmeter method, when the value of power factor is less than 0.5 lagging (a) one of the wattmeters will read zero (b) both give the same readings (c) one of the wattmeter connections will have to be reversed (d) pressure coil of the wattmeter will become ineffective. Ans:C [55] When using ohmmeter, applied voltage is to be disconnected from the circuit because (a) Voltage source will increase resistance (b) Current will decrease resistance (c) the ohmmeter has its own internal battery (d) non of the above Ans: C [56] Which wave has the least form factor? (a) Square wave (b) Rectangular wave (c) Sine wave (d) Triangular wave Ans: A [57] With a sweep time 10ms across the screen the approx. horizontal sawtooth frequency will be (a) 50Hz (b) 100Hz (c) 1kHz (d) 500Hz
[59] It is found that 10A current passes through a resistor of 10ohms. The resistor has 5% tolerance . The error in measurement of current can be as high as 5%. What is max error in measurement of power, calculated from measured value of I and the nominal value of resistor? (a) 100 W (b) 150W (c)50W (d) 200W Ans: B [60] A resistor of 10Kohms with 5% tolerance is connected in parallel with a 5Kohms resistor of 10% tolerance. What is the tolerance limit for the parallel network? (a) 5% (b) 6.67% (c) 10% (d) 8.33% Ans: D [61] The resistance offered to the passage of an in-varying current by a column of mercury at the temperature of melting ice of mass 14.4521 gms of uniform crosssectional area and length 106.3cm is (a) Standard ohm (b) One international ohm (c) One ohm according to SI units (d) One ohm according to working standards Ans: B
[62] The most preferred material for the control spring is (a) German silver (b) Platinum silver (c) Silicon bronze (d) Phosphor bronze Ans: D [63] A mulliammeter can be used as (a) Voltmeter and ammeter (b) Wattmeter (c) Ohmmeter (d) Frequency meter Ans:A [64] Which instrument has identical calibration for ac as well as dc values? (a) Hot wire type (b) Moving coil type (c) Induction type (d) Moving iron type Ans: A [65] An instrument to be used for measurement and control should preferably have (a) Dead zone and dead time (b) Linear output and fast response (c) Non-linear output (d) A highly damped response Ans:B 66] The current coil of a wattmeter is connected to the CT of R-phase. The potential coil is connected across Y and B phases. The wattmeter measures (a) Active power in R phase (b) Active power of Y phase (c) Reactive power of R phase (d) Power proportional to 3 phase power if the load is balanced Ans: C [67] The problem of Electro-static coupling in a transformer is acute at (a) Low frequencies
(b) Power frequencies (c) High frequencies (d) High load on the transformer Ans: C [68] Which meter is suitable for the measurement of 10mV at 50MHz? (a) Moving iron voltmeter (b) VTVM (c) Moving coil voltmeter (d) CRO Ans:D [69] It can be stated that (a) CT operates at almost the same flux density as a PT (b) CT operates with a higher flux density than PT (c) CT operates with considerably lower flux density than a PT (d) no generalisation can be made with regard to the flux densities in CT and PT Ans: C [70] The thermocouple instruments do not have (a) High sensitivity (b) Absence of frequency error (c) Independence of ambient temperature (d) High degree of measuring accuracy Ans: D [71] Some wire- wound resistors have bifilar winding. This type of winding is used to (a) Increase the thermal stability (b) Reduce the tolerance (c) Reduce the inductance of winding (d) Double the power rating of the resistor Ans: C [72] Wien bridge is useful for measuring (a) Very high frequency (b) Low frequency (c) Medium frequency (d) High frequency Ans: D
[73] A megger is usually (a) Moving iron type instrument (b) Electro-static type instrument (c) Hot-wire type instrument (d) Moving coil type instrument Ans: D [74] A moving iron ammeter may be compensated for frequency errors by (a) a shunt resistance (b) a series inductance (c) shunt capacitance (d) series resistance Ans: C [75] Ryall crest voltmeter is used for measurement of (a) AC voltage of any form (b) Low frequency voltage (c) High DC voltage (d) High AC voltage Ans:D [76] Jewels are used in instruments for the purpose of (a) Damping (b) Torque control (c) Suppressing noise (d) Bearing Ans: D [77] The thermocouple instrument will measure (a) Current (b) Voltage (c) Flux (d) None of the above Ans: D [78] The differentiator has a transfer function whose (a) Phase increases linearly with frequency (b) Amplitude remains constant (c) Amplitude increases linearly with
frequency (d) Amplitude decreases linearly with frequency Ans: A [79] Introduction of integral action in the forward path of a unity feedback system results in a (a) Marginally stable system (b) System with no steady state error (c) System with increase stability margin (d) System with better speed of response Ans: A [80] The Fourier transform of a signal h(t) is H(jω) = (2cosω)(sin2ω)/ω. The value of h(0) is (a) 1/4 (b) 1/2 (c) 1 (d) 2 Ans: C [81] A Linear Time Invariant system with an impulse response h(t) produces output y(t) when input x(t) is applied. When the input x(t-τ) is applied to a system with impulse response h(t-τ), the output will be (a) y(t) (b) y(2(t-τ)) (c) y(t-τ) (d) y(t-2τ) Ans:D [82] The system represented by the inputoutput relationship y(t)= 5t∫-∞ x(τ)dτ, t>0 is (a) Linear and casual (b) Linear but not casual (c) Casual but not linear (d) Neither linear nor casual Ans: B [83] For the system 2/(s+1), the approximate time taken for a step response to reach 98% of its final value is
(a) 1s (b) 2s (c) 4s (d) 8s Ans: C [84] Given the finite length input x[n] and the corresponding finite length output y[n] of an LTI system as shown below, the impulse response h[n] of the system is (a) h[n]={1,0,0,1} (b) h[n]={1,0,1} (c) h[n]={1,1,1,1} (d) h[n]={1,1,1} Ans:C [85] It is required to construct a counter to count upto 100(decimal). The minimum number of flipflops required to construct the counter is a) 8 b) 7 c) 6 d) 5 Ans:A [86] The gate that assumes the 1 state, if and only if the input does not take a 1 state is called........ a) AND gate b) NOT gate c) NOR gate d) Both b and c Ans: D [87] For NOR circuit SR flip flop the not allowed condition is.... a) S=0, R=0 b) S=0, R=1 c) S=1, R=1 d) S=1, R=0 Ans: C . When S=R=1 the output is subject to unpredictable behaviour when S and R return to 0 simultaneously.
[88] A bistable multivibrator is a a) Free running oscillator b) Triggered oscillator c) Saw tooth wave generator d) Crystal oscillator Ans: B [89] For a large values of |VDS|, a FET behave as a) Voltage controlled resistor b) Current controlled current source c) Voltage controlled current source d) Current controlled resistor Ans: C [90] When a step input is given to an opamp integrator, the output will be a) a ramp b) a sinusoidal wave c) a rectangular wave d) a triangular wave with dc bias Ans: A [91] In a full-wave rectifier without filter, the ripple factor is a) 0.482 b) 1.21 c) 1.79 d) 2.05 Ans: A [92] Hysteresis is desirable in Schmitttrigger, because a) Energy is to be stored/discharged in parasitic capacitance b) Effects of temperature would be compensated c) Devices in the circuit should be allowed time for saturation and desaturation d) It would prevent noise from causing false triggering Ans:C [93] For a 10-bit DAC, the Resolution is defined by which of the following
a) 1024 b) 1/1024 c) 10 d) None Ans:B
b) As a dynamic memory c) To realise a sequential logic d) To realise a combinational logic Ans: D
[94] SRAM full form is a) Serial Read Access Memory b) Static Random Access Memory c) Static Read-only Access memory Ans: B
[98] A dynamic RAM consists of a) 6 Transistors b) 2 Transistors and 2 Capacitors c) 1 Transistor and 1 Capacitor d) 2 Capacitor only Ans:C
[95] What are the minimum number of 2 to 1 multiplexers required to generate a 2 input AND gate and a 2 input Ex-OR gate? a) 1 and 2 b) 1 and 3 c) 1 and 1 d) 2 and 2 Ans:A
[99] When a CPU is interrupted, it a) Stops execution of instructions b) Acknowledges interrupt and branches of subroutine c) Acknowledges interrupt and continues d) Acknowledges interrupt and waits for the next instruction from the interrupting device. Ans: B
[96]The output of a logic gate is ‘1’ when all its inputs are at logic ‘0’. Then gate is either a) A NAND or an EX-OR gate b) A NOR or an EX-NOR gate c) An OR or a EX-NOR gate d) An AND or an Ex-OR gate Ans: B
[100] The period of the signal x(t) = 8 sin (0.8πt + π /4) is A. 0.4πs B. 0.8πs C. 1.25s D. 2.5s Ans:D
[97] A PLA can be used a) As a microprocessor
