Previous Year Questions
71 questions — organised by subject with solutions and explanations.
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The switch S in the circuit of the figure is initially closed, it is opened at time t=0. You may neglect the zener diode forward voltage drops. What is the behavior of for t 0 ?
The common emitter forward current gain of the transistor shown is . The transistor is operating in
The circuit shown in the figure is
IC 555 in the adjacent figure is configured as an astable multi-vibrator. It is enabled to to oscillate at t=0 by applying a high input to pin 4. The pin description is : 1 and 8-supply; 2-trigger; 4-
The input signal shown in the figure is a 1 kHz square wave voltage that alternates between +7 V and -7 V with a 50% duty cycle. Both transistor have the same current gain which is large. The circuit
The three-terminal linear voltage regulator is connected to a 10 load resistor as shown in the figure. If is 10 V, what is the power dissipated in the transistor ?
The system shown in the figure is
If the loop gain K of a negative feed back system having a loop transfer function is to be adjusted to induce a sustained oscillation then
The system is to be compensated such that its gain-crossover frequency becomes same as its uncompensated phase crossover frequency and provides a 45 phase margin. To achieve this, one may use
The state equation for the current in the network shown below in terms of the voltage and the independent source V, is given by
The system shown in figure below can be reduced to the form with
Consider the R-L-C circuit shown in figure For a step-input , the overshoot in the output will be
Consider the feedback system shown below which is subjected to a unit step input. The system is stable and has following parameters . The steady state value of z is
Consider the R-L-C circuit shown in figure If the above step response is to be observed on a non-storage CRO, then it would be best have the as a
If , and then for , the Nyquist plot for becomes asymptotic to the line
A,B,C and D are input, and Y is the output bit in the XOR gate circuit of the figure below. Which of the following statements about the sum S of A,B,C,D and Y is correct ?
The associated figure shows the two types of rotate right instructions , available in a microprocessor where Reg is a 8-bit register and C is the carry bit. The rotate left instructions are similar ex
The associated figure shows the two types of rotate right instructions R_1, R_2, available in a microprocessor where Reg is a 8-bit register and C is the carry bit. The rotate left instructions L1 and
The Octal equivalent of HEX and number AB.CD is
Which one of the following statements regarding the INT (interrupt) and the BRQ (but request) pins in a CPU is true?
The matrix A given below in the node incidence matrix of a network. The columns correspond to branches of the network while the rows correspond to nodes. Let denote the vector of branch voltages while
In the circuit shown in figure. Switch is initially closed and is open. The inductor L carries a current of 10 A and the capacitor charged to 10 V with polarities as indicated. is closed at t= and is
In the figure, transformer has two secondaries, all three windings having the same number of turns and with polarities as indicated. One secondary is shorted by a 10 resistor R, and the other by a 15
In the figure given below all phasors are with reference to the potential at point "O". The locus of voltage phasor as R is varied from zero to infinity is shown by
The R-L-C series circuit shown in figure is supplied from a variable frequency voltage source. The admittance-locus of the R-L-C network at terminals AB for increasing frequency is
A bridge circuit is shown in the figure below. Which one of the sequence given below is most suitable for balancing the bridge ?
The probes of a non-isolated, two channel oscillocope are clipped to points A, B and C in the circuit of the adjacent figure. is a square wave of a suitable low frequency. The display on are as shown
A three-phase, three-stack, variable reluctance step motor has 20 poles on each rotor and stator stack. The step angle of this step motor is
A single-phase, 50-kVA, 250 V/500 V two winding transformer has an efficiency of 95% at full load, unity power factor. If it is re-configured as a 500 V/750 V auto-transformer, its efficiency at its n
A three-phase synchronous motor connected to ac mains is running at full load and unity power factor. If its shaft load is reduced by half, with field current held constant, its new power factor will
A three phase squirrel cage induction motor has a starting current of seven times the full load current and full load slip of 5% If a starting torque of 0.5 per unit is required then the per unit star
A 100 kVA, 415 V(line), star-connected synchronous machine generates rated open circuit voltage of 415 V at a field current of 15 A. The short circuit armature current at a field current of 10 A is eq
The electromagnetic torque of a drive and its connected load torque are as shown below. Out of the operating points A, B, C and D, the stable ones are
A three-phase squirrel cage induction motor has a starting torque of 150% and a maximum torque of 300% with respect to rated torque at rated voltage and rated frequency. Neglect the stator resistance
In a transformer, zero voltage regulation at full load is
The dc motor, which can provide zero speed regulation at full load without any controller is
An inductor designed with 400 turns coil wound on an iron core of 16 cross sectional area and with a cut of an air gap length of 1 mm. The coil is connected to a 230 V, 50 Hz ac supply. Neglect coil r
A solid sphere made of insulating material has a radius R and has a total charge Q distributed uniformly in its volume. What is the magnitude of the electric field intensity, E, at a distance inside t
Divergence of the vector field is
A single-phase, 230 V, 50 Hz ac mains fed step down transformer (4:1) is supplying power to a half-wave uncontrolled ac-dc converter used for charging a battery(12 V dc) with the series current limiti
A three-phase, fully controlled thyristor bridge converter is used as line commutated inverter to feed 50 kW power 420 V dc to a three-phase, 415 V(line), 50 Hz ac mains. Consider dc link current to b
A single-phase fully controlled thyristor bridge ac-dc converter is operating at a firing angle of 25 and an overlap angle of 10 with constant dc output current of 20 A. The fundamental power factor (
In the circuit of adjacent figure the diode connects the ac source to a pure inductance L. The diode conducts for
The circuit in the figure is a current commutated dc-dc chopper where, is the main SCR and is the auxiliary SCR. The load current is constant at 10 A. is ON. is trigged at t = 0. is turned OFF between
A single-phase voltages source inverter is controlled in a single pulse-width modulated mode with a pulse width of 150 in each half cycle. Total harmonic distortion is defined as , where is the rms va
A single phase full-wave half-controlled bridge converter feeds an inductive load. The two SCRs in the converter are connected to a common DC bus. The converter has to have a freewheeling diode.
A 1:1 Pulse Transformer (PT) is used to trigger the SCR in the below figure. The SCR is rated at 1.5 kV, 250 A with =250 mA, =150 mA, and =150 mA, =100 mA. The SCR is connected to an inductive load, w
"Six MOSFETs connected in a bridge configuration (having no other power device) must be operated as a Voltage Source Inverter (VSI)". This statement is
A voltage source inverter is used to control the speed of three-phase, 50 Hz, squirrel cage induction motor. Its slip for rated torque is 4%. The flux is maintained at rated value. If the stator resis
A three-phase, 440 V, 50 Hz ac mains fed thyristor bridge is feeding a 440 V dc, 15 kW, 1500 rpm separately excited dc motor with a ripple free continuos current in the dc link under all operating con
Consider the transformer connections in a part of a power system shown in the figure. The nature of transformer connections and phase shifts are indicated for all but one transformer. Which of the fol
Two regional systems, each having several synchronous generators and loads are inter connected by an ac line and a HVDC link as shown in the figure. Which of the following statements is true in the st
Consider the two power systems shown in figure A below, which are initially not interconnected, and are operating in steady state at the same frequency. Separate load flow solutions are computed indiv
An isolated 50 Hz synchronous generator is rated at 15 MW which is also the maximum continuous power limit of its prime mover. It is equipped with a speed governor with 5% droop. Initially, the genera
The figure below shows a three phase self-commutated voltage source converter connected to a power system. The converter's dc bus capacitor is marked as C in the figure. The circuit in initially opera
The incremental cost curves in Rs/MWhr for two generators supplying a common load of 700 MW are shown in the figures. The maximum and minimum generation limits are also indicated. The optimum generati
The total reactance and total suspectance of a lossless overhead EHV line, operating at 50 Hz, are given by 0.045 pu and 1.2 pu respectively. If the velocity of wave propagation is km/s, then the appr
Consider the protection system shown in the figure below. The circuit breakers numbered from 1 to 7 are of identical type. A single line to ground fault with zero fault impedance occurs at the midpoin
Consider a synchronous generator connected to an infinite bus by two identical parallel transmission line. The transient reactance 'x' of the generator is 0.1 pu and the mechanical power input to it i
Considered a bundled conductor of an overhead line consisting of three identical sub-conductors placed at the corners of an equilateral triangle as shown in the figure. If we neglect the charges on th
A three phase balanced star connected voltage source with frequency rad/s is connected to a star connected balanced load which is purely inductive. The instantaneous line currents and phase to neutral
Suppose we define a sequence transformation between "a-b-c" and "p-n-o" variables as follows: where and k and is a constant. Now, if it is given that : and then,
A 230 V (Phase), 50 Hz, three-phase, 4-wire, system has a phase sequence ABC. A unity power-factor load of 4 kW is connected between phase A and neutral N. It is desired to achieve zero neutral curren
A signal is processed by a causal filter with transfer function G(s). For a distortion free output signal wave form, G(s) must
A signal is processed by a causal filter with transfer function G(s). is a low pass digital filter with a phase characteristics same as that of the above question if
Let a signal be applied to a stable linear time invariant system. Let the corresponding steady state output be represented as . Then which of the following statement is true?
Consider the discrete-time system shown in the figure where the impulse response of G(z) is g(0)=0, g(1)=g(2)=1, g(3)=g(4)=...= 0 This system is stable for range of values of K
If u(t), r(t) denote the unit step and unit ramp functions respectively and u(t)*r(t) their convolution, then the function u(t+1)*r(t-2) is given by
, are Z transforms of two signals x[n],y[n] respectively. A linear time invariant system has the impulse response h[n] defined by these two signals as h[n] = x[n-1] * y[n] where * denotes discrete tim
The frequency spectrum of a signal is shown in the figure. If this is ideally sampled at intervals of 1 ms, then the frequency spectrum of the sampled signal will be
A signal is given by Which among the following gives the fundamental fourier term of x(t)?