Previous Year Questions
86 questions — organised by subject with solutions and explanations.
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A voltage signal is applied to the circuit with ideal diodes, as shown in figure, The maximum, and minimum values of the output waveform of the circuit are respectively
For the circuit of figure with an ideal operational amplifier, the maximum phase shift of the output with reference to the input is
The circuit of figure shows a 555 Timer IC connected as an astable multivibrator. The value of the capacitor C is 10 nF. The values of the resistors for a frequency of 10 kHz and a duty cycle of 0.75
Assuming the operational amplifier to be ideal, the gain for the circuit shown in figure is
In the circuit of figure, assume that the transistor has = 99 and = 0.7 V. The value of collector current of the transistor is approximately
For the n-channel enhancement MOSFET shown in figure, the threshold voltage = 2 V. The drain current of the MOSFET is 4 mA when the drain resistance is 1 k . If the value of is increased to 4 k , drai
The variation of drain current with gate-to-source voltage ( - characteristic) of a MOSFET is shown in figure. The MOSFET is
In the circuit shown in figure, the current gain ( ) of the ideal transistor is 10. The operating point of the transistor ( ) is
The following equation defines a separately excited dc motor in the form of a differential equation The above equation may be organized in the state-space form as follows where the P matrix is given b
The roots of the closed loop characteristic equation of the system shown in figure are
The asymptotic Bode plot of the transfer function is given in figure. The error in phase angle and dB gain at a frequency of are respectively
A second order system starts with an initial condition of without any external input. The state transition matrix for the system is given by . The state of the system at the end of 1 second is given b
The loop gain GH of a closed loop system is given by the following expression The value of K for which the system just becomes unstable is
The block diagram of a control system is shown in figure. The transfer function G(s) = Y(s)/U(s) of the system is
A control system is defined by the following mathematical relationship The response of the system as is
A control system with certain excitation is governed by the following mathematical equation The natural time constant of the response of the system are
A lead compensator used for a closed loop controller has the following transfer function For such a lead compensator
The block diagram shown in figure gives a unity feedback closed loop control system. The steady state error in the response of the above system to unit step input is
When a program is being executed in an 8085 Microprocessors, its Program Counter contains
The boolean expression can be simplified to
Figure shows a 4 to 1 MUX to be used to implement the sum S of a 1-bit full adder with input bits P and Q and the carry input Cin. Which of the following combinations of inputs to and of the MUX will
The shift register shown in figure is initially loaded with the bit pattern 1010. Subsequently the shift register is clocked, and with each clock pulse the pattern gets shifted by one bit position to
A memory system has a total of 8 memory chips, each with 12 address lines and 4 data lines, The total size of the memory system is
The following program is written for an 8085 microprocessor to add two bytes located at memory addresses 1FFE and 1FFF LXI H, 1FFE MOV B, M INR L MOV A, M ADD B INR L MOV M, A XOR A On completion of t
An X-Y flip-flop, whose Characteristic Table is given below is to be implemented using a J-K flip flop
Two ac sources feed a common variable resistive load as shown in figure. Under the maximum power transfer condition, the power absorbed by the load resistance is
The h-parameters for a two-port network are defined by . For the two-port network shown in figure, the value of is given by
In the circuit of figure, the magnitudes of and are twice that of . Given that f = 50 Hz, the inductance of the coil is
In the figure, . The venin impedance seen form X-Y is
In the circuit shown in figure, the switch S is closed at time (t=0). The voltage across the inductance at t= , is
The effect of stray magnetic field on the actuating torque of a portable instrument is maximum when the operating field of the instrument and the stray fields are
A wattmeter reads 400 W when its current coil is connected in the R-phase and its pressure coil is connected between this phase and the neutral of a symmetrical 3-phase system supplying a balanced sta
A 500A/5A, 50 Hz transformer has a bar primary. The secondary burden is a pure resistance of 1 and it draws a current of 5 A. If the magnetic core requires 250 AT for magnetization, the percentage rat
Group-II represents the figures obtained on a CRO screen when the voltage signals and are given to its X and Y plates respectively and is changed. Choose the correct value of from Group-I to match wit
A Manganin swap resistance is connected in series with a moving coil ammeter consisting of a milli-ammeter and a suitable shunt in order to
The items in Group-I represent the various types of measurements to be made with a reasonable accuracy using a suitable bridge. The items in Group-II represent the various bridges available for this p
The simplified block diagram of a 10-bit A/D converter of dual slope integrator type is shown in figure. The 10-bit counter at the output is clocked by a 1 MHz clock. Assuming negligible timing overhe
The inductance of a certain moving-iron ammeter is expressed as L = , where is the deflection in radians from the zero position. The control spring torque is Nm/radian. The deflection of the pointer i
A rectifier type ac voltmeter of a series resistance , an ideal full-wave rectifier bridge and a PMMC instrument as shown in figure. The internal. resistance of the instrument is 100 and a full scale
A reading of 120 is obtained when standard inductor was connected in the circuit of a Q-meter and the variable capacitor is adjusted to value of 300 pF. A lossless capacitor of unknown value is then c
The voltage-flux adjustment of a certain 1-phase 220 V induction watt-hour meter is altered so that the phase angle between the applied voltage and the flux due to it is 85 (instead of 90 ). The error
A sinple phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is
An ac induction motor is used for a speed control application. It is driven from an inverter with a constant V/f control. The motor name-plate details are as follows (no. of poles = 2) V:415 V Ph:3 f:
No-load test on a 3-phase induction motor was conducted at different supply voltage and a plot of input power versus voltage was drawn. This curve was extrapolated to intersect the y-axis. The interse
Figure shows an ideal single-phase transformer. The primary and secondary coils are wound on the core as shown. Turns ratio . The correct phasors of voltages , , currents , and core flux are as shown
Figure shows a -Y connected, 3-phase distribution transformer used to step down the voltage from 11000 V to 415 V line-to-line. It has two switches and . Under normal conditions is closed and is open.
The speed/torque regimes in a dc motor and the control methods suitable for the same are given respectively in Group-II and Group-I
Figure shows an ideal three-winding transformer. The three windings 1, 2, 3 of the transformer are wound on the same core as shown. The turns ratio is 4:2:1. A resistor of 10 is connected across windi
A dc series motor driving an electric train faces a constant power load. It is running at rated speed and rated voltage. If the speed has to be brought down to 0.25 p.u. the supply voltage has to be a
Following are some of the properties of rotating electrical machines P. Stator winding current is dc, rotor winding current is ac. Q. Stator winding current is ac, rotor winding current is dc. R. Stat
Curves X and Y in figure denote open circuit and full-load zero power factor(zpf) characteristics of a synchronous generator. Q is a point on the zpf characteristics at 1.0 p.u. voltage. The vertical
When stator and rotor windings of a 2-pole rotating electrical machine are excited, each would produce a sinusoidal mmf distribution in the airgap with peal values and respectively. The rotor mmf lags
Group-I lists different applications and Group-II lists the motors for these applications. Match the application with the most suitable motor and choose the right combination among the choices given t
A stand alone engine driven synchronous generator is feeding a partly inductive load. A capacitor is now connected across the load to completely nullify the inductive current. For this operating condi
A 4-pole, 3-phase, double-layer winding is housed in a 36-slot stator for an ac machine with 60c phase spread. Coil span is 7 short pitches. Number of slots in which top and bottom layers belong to di
A single-phase induction motor with only the main winding excited would exhibit the following response at synchronous speed
A round rotor generator with internal voltage = 2.0 p.u. and X = 1.1 p.u. is connected to a round rotor synchronous motor with internal voltage = 1.3 p.u. and X = 1.2 p.u. The reactance of the line co
A 3-phase induction motor is driving a constant torque load at rated voltage and frequency. If both voltage and frequency are halved, following statements relate to the new condition if stator resista
To conduct load test on a dc shunt motor, it is coupled to a generator which is identical to the motor. The field of the generator is also connected to the same supply source as the motor. The armatur
Two conductors are carrying forward and return current of +I and -I as shown in figure. The magnetic field intensity H at point P is
A point charge of +1 nC is placed in a space with permittivity of F/m as shown in figure. The potential difference between two points P and Q at distance of 40 mm and 20 mm respectively from the point
A parallel plate capacitor has an electrode area of 100 , with spacing of 0.1 mm between the electrodes. The dielectric between the plates is air with a permittivity of F/m. The charge on the capacito
A composite parallel plate capacitor is made up of two different dielectric material with different thickness ( and ) as shown in figure. The two different dielectric materials are separated by a cond
Two infinite strips of width w m in x -direction as shown in figure, are carrying forward and return currents of +I and -I in the z - direction. The strips are separated by distance of x m. The induct
Figure shows a MOSFET with an integral body diode. It is employed as a power switching device in the ON and OFF states through appropriate control. The ON and OFF states of the switch are given on the
Figure shows a thyristor with the standard terminations of anode (A), cathode (K), gate (G) and the different junctions named , and . When the thyristor is turned on and conducting
A chopper is employed to charge a battery as shown in figure. The charging current is 5 A. The duty ratio is 0.2. The chopper output voltage is also shown in the figure. The peak to peak ripple curren
With reference to the output wave form given in the figure, the output of the converter will be free from 5th harmonic when
A phase-controlled half-controlled single-phase converter is shown in figure. The control angle The output dc voltage wave shape will be a s shown in
A fully controlled natural commutated 3-phase bridge rectifier is operating with a firing angle , The peak to peak voltage ripple expressed as a ratio of the peak output dc voltage at the output of th
An inverter has a periodic output voltage with the output wave form as shown in figure When the conduction angle , the rms fundamental component of the output voltage is
three-phase alternator generating unbalanced voltages is connected to an unbalanced load through a 3-phase transmission line as shown in figure. The neutral of the alternator and the star point of the
A dc distribution system is shown in figure with load current as marked. The two ends of the feeder are fed by voltage sources such that . The value of the voltage for a minimum voltage of 220 V at an
A surge of 20 kV magnitude travels along a lossless cable towards its junction with two identical lossless overhead transmission lines. The inductance and the capacitance of the cable are 0.4 mH and 0
A 3-phase 11 kV generator feeds power to a constant power unity power factor load of 100 MW through a 3-phase transmission line. The line-to line voltage at the terminals of the machine is maintained
The ABCD parameters of a 3-phase overhead transmission line are , and S. At no-load condition a shunt inductive, reactor is connected at the receiving end of the line to limit the receiving-end voltag
A balanced delta connected load of (8 + j6) per phase is connected to a 400 V, 50 Hz, 3-phase supply lines. If the input power factor is to be improved to 0.9 by connecting a bank of star connected ca
The interrupting time of a circuit breaker is the period between the instant of
Choose two appropriate auxiliary components of a HVDC transmission system from the following P. D.C line inductor Q. A.C line inductor R. Reactive power sources S. Distance relays on D.C line T. Serie
A list of relays and the power system components protected by the relays are given in Group-I and Group-II respectively. Choose the correct match from the four choices given below:
The bus impedance matrix of a 4-bus power system is given by A branch having an impedance of is connected between bus 2 and the reference. Then the values of and of the bus impedance matrix of the mod
Bundled conductors are mainly used in high voltage overhead transmission lines to
A power system consist of 300 buses out of which 20 buses are generator bus, 25 buses are the ones with reactive power support and 15 buses are the ones with fixed shunt capacitors. All the other buse
A generator delivers power of 1.0 p.u. to an infinite bus through a purely reactive network. The maximum power that could be delivered by the generator is 2.0 p.u. A three-phase fault occurs at the te
Incremental fuel costs (in some appropriate unit) for a power plant consisting of three generating units are Where is the power in MW generated by unit i for i=1,2 and 3. Assume that all the three uni
A 20-MVA, 6.6-kV, 3-phase alternator is connected to a 3-phase transmission line. The per unit positive sequence, negative sequence and zero sequence impedances of the alternator are j0.1, j0.1 and j0