Previous Year Questions
74 questions — organised by subject with solutions and explanations.
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Consider the circuit shown in figure. If the of the transistor is 30 and is 20 mA and the input voltage is +5 V, the transistor would be operating in
What are the states of the three ideal diodes of the circuit shown in figure ?
For a given sinusoidal input voltage, the voltage waveform at point P of the clamper circuit shown in figure will be
A relaxation oscillator is made using OPAMP as shown in figure. The supply voltages of the OPAMP are 12 V. The voltage waveform at point P will be
Assuming the diodes and of the circuit shown in figure to be ideal ones, the transfer characteristics of the circuit will be
For a system with the transfer function , the matrix A in the state space form X=AX+Bu is equal to
The Bode magnitude plot of is
The algebraic equation is given. F(s) = 0 has
Consider the following Nyquist plots of loop transfer functions over . Which of these plots represent a stable closed loop system ?
A closed-loop system has the characteristic function . Its root locus plot against K is
It is required to design an anti-aliasing filter for an, 8 bit ADC. The filter is a first order RC filter with R = 1 and C = 1F. The ADC is designed to span a sinusoidal signal with peak to peak ampli
A MUX is used to implement a 3-input Boolean function as shown in figure. The Boolean function F(A,B,C) implemented is
A student has made a 3-bit binary down counter and connected to the R-2R ladder type DAC [Gain=(-1K /2R)] as shown in figure to generate a staircase waveform. The output achieved is different as shown
A software delay subroutine is written as given below : DELAY : MVI H, 255D MVI L, 255D LOOP : DCR L JNZ LOOP DCR H JNZ LOOP How many times DCR L instruction will be executed ?
A TTL NOT gate circuit is shown in figure. Assuming =0.7 V of both the transistors, if =3.0 V, then the states of the two transistors will be
In an 8085 A microprocessor based system, it is desired to increment the contents of memory location whose address is available in (D,E) register pair and store the result in same location. The sequen
In the circuit shown in the figure, the current source I=1A, the voltage source V=5 V, The currents (in A) through and through the voltage source V respectively will be
An ideal capacitor is charged to a voltage and connected at t=0 across an ideal inductor L. (The circuit now consists of a capacitor and inductor alone). If we let , the voltage across the capacitor a
An energy meter connected to an immersion heater (resistive) operating on an AC 230 V, 50 Hz, AC single phase source reads 2.3 units (kWh) in 1 hour. The heater is removed from the supply and now conn
In the figure the current source is A, R=1 , the impedances are and . The Thevenin equivalent looking into the circuit across X-Y is
The circuit shown in the figure is energized by a sinusoidal voltage source at a frequency which causes resonance with a current of I . The phasor diagram which is applicable to this circuit is
The parameter type and the matrix representation of the relevant two port parameters that describe the circuit shown are
The parameters of the circuit shown in the figure are . If , then output voltage, input impedance and output impedance respectively are
A variable w is related to three other variables x, y, z as w=xy/z. The variables are measured with meters of accuracy 0.5% reading, 1% of full scale value and 1.5% reading. The actual readings of the
A 200/1 Current transformer (CT) is wound with 200 turns on the secondary on a toroidal core. When it carries a current of 160 A on the primary, the ratio and phase errors of the CT are found to be -0
A current of A is passed through three meters. They are a centre zero PMMC meter, a true rms meter and a moving iron instrument. The respective reading (in A) will be
are the opposite arms of a Wheatstone bridge as are . The source voltage is applied across . Under balanced conditions which one of the following is true
The time/div and voltage/div axes of an oscilloscope have been erased. A student connects a 1 kHz, 5 V p-p square wave calibration pulse to channel-1 of the scope and observes the screen to be as show
A sampling wattmeter (that computes power from simultaneously sampled values of voltage and current) is used to measure the average power of a load. The peak to peak voltage of the square wave is 10 V
A 3-phase, 4-pole, 400 V, 50 Hz, star connected induction motor has following circuit parameters The starting torque when the motor is started direct-on-line is (use approximate equivalent circuit mod
A 220 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased
A 300 kVA transformer has 95% efficiency at full load 0.8 pf lagging and 96% efficiency at half load, unity pf. What is maximum efficiency(in %) at unity pf load?
A 3-phase, 10 kW, 400 V, 4-pole, 50Hz, star connected induction motor draws 20 A on full load. Its no load and blocked rotor test data are given below. Neglecting copper loss in no load test and core
Two transformers are to be operated in parallel such that they share load in proportion to their kVA ratings. The rating of the first transformer is 500 kVA and its pu leakage impedance is 0.05 pu. If
In transformers, which of the following statements is valid ?
The three limbed non ideal core shown in the figure has three windings with nominal inductances L each when measured individually with a single phase AC source. The inductance of the windings as conne
A 3-phase, 400 V, 5 kW, star connected synchronous motor having an internal reactance of 10 is operating at 50% load, unity p.f. Now, the excitation is increased by 1%. What will be the new load in pe
A 4 pole, 50 Hz, synchronous generator has 48 slots in which a double layer winding is housed. Each coil has 10 turns and is short pitched by an angle to 36 electrical. The fundamental flux per pole i
For a single phase capacitor start induction motor, which of the following statements is valid ?
A synchronous generator is feeding a zero power factor (lagging) load at rated current. The armature reaction is
In a DC machine, which of the following statements is true ?
The speed of a 4-pole induction motor is controlled by varying the supply frequency while maintaining the ratio of supply voltage to supply frequency (V/f) constant. At rated frequency of 50 Hz and ra
Which of the following statement holds for the divergence of electric and magnetic flux densities ?
Consider the following statements with reference to the equation (1) This is a point form of the continuity equation. (2) Divergence of current density is equal to the decrease of charge per unit volu
An SCR having a turn ON times of 5 sec, latching current of 50 mA and holding current of 40 mA is triggered by a short duration pulse and is used in the circuit shown in figure. The minimum pulse widt
A single-phase bridge converter is used to charge a battery of 200 V having an internal resistance of 0.2 as shown in figure. The SCRs are triggered by a constant dc signal. If gets open circuited, wh
The speed of a 3-phase, 440 V, 50 Hz induction motor is to be controlled over a wide range from zero speed to 1.5 time the rated speed using a 3-phase voltage source inverter. It is desired to keep th
A single-phase half wave uncontrolled converter circuit is shown in figure. A 2-winding transformer is used at the input for isolation. Assuming the load current to be constant and , the current wavef
A solar cell of 350 V is feeding power to an ac supply of 440 V, 50 Hz through a 3-phase fully controlled bridge converter. A large inductance is connected in the dc circuit to maintain the dc current
A voltage commutation circuit is shown in figure. If the turn-off time of the SCR is 50 sec and a safety margin of 2 is considered, then what will be the approximate minimum value of capacitor require
A 3-phase fully controlled bridge converter with free wheeling diode is fed from 400 V, 50 Hz AC source and is operating at a firing angle of 60 . The load current is assumed constant at 10 A due to h
A voltage commutated chopper operating at 1 kHz is used to control the speed of dc as shown in figure. The load current is assumed to be constant at 10 A. The average output voltage of the chopper wil
A single-phase inverter is operated in PWM mode generating a single-pulse of width 2d in the centre of each half cycle as shown in figure. It is found that the output voltage is free from 5th harmonic
A single phase transmission line and a telephone line are both symmetrically strung one below the other, in horizontal configurations, on a common tower, The shortest and longest distances between the
For a power System the admittance and impedance matrices for the fault studies are as fallows The pre-fault voltages are 1.0 pu. at all the buses. The system was unloaded prior to the fault. A solid 3
For a power system the admittance and impedance matrices for the fault studies are as fallows The pre-fault voltages are 1.0 pu. at all the buses. The system was unloaded prior to the fault. A solid 3
A 400 V, 50 Hz, three phase balanced source supplies power to a star connected load whose rating is 12 kVA, 0.8 pf (lag). The rating (in kVAR) of the delta connected (capacitive) reactive power bank n
A generator feeds power to an infinite bus through a double circuit transmission line. A 3-phase fault occurs at the middle point of one of the lines. The infinite bus voltage of the generator is 1.1
A generator is connected through a 20 MVA, 13.8/138 kV step down transformer, to a transmission line. At the receiving end of the line a load is supplied through a step down transformer of 10 MVA, 138
The Gauss Seidel load flow method has following disadvantages. Tick the incorrect statement
Three identical star connected resistors of 1.0 pu are connected to an unbalanced 3-phase supply. The load neutral is isolated. The symmetrical components of the line voltages in pu. are: . If all the
An HVDC link consist of rectifier, inverter transmission line and other equipments. Which one of the following is true for this link ?
The concept of an electrically short, medium and long line is primarily based on the
Keeping in view the cost and overall effectiveness, the following circuit breaker is best suited for capacitor bank switching
The A, B, C , D constants of a 220 kV line are : , , . If the sending end voltage of the line for a given load delivered at nominal voltage is 240 kV, the % voltage regulation of the line is
In a biased differential relay the bias is defined as a ratio of
y[n] denotes the output and x[n] denotes the input of a discrete-time system given by the difference equation y[n]-0.8y[n-1]=x[n]+1.25x[n+1]. Its right-sided impulse response is
x(t) is a real valued function of a real variable with period T. Its trigonometric Fourier Series expansion contains no terms of frequency (2k)/T; k=1,2... Also, no sine terms are present. Then x(t) s
A discrete real all pass system has a pole at z = 2 30 : it, therefore
The discrete-time signal where denotes a transform-pair relationship, is orthogonal to the signal
, is the input and , is the output of a discrete-time LTI system. The system impulse response h[n] will be
The running integration, given by
Which of the following is true?
A continuous-time system is described by , where y(t) is the output and x(t) is the input. y(t) is bounded