Previous Year Questions
74 questions — organised by subject with solutions and explanations.
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Consider the inverting amplifier, using an ideal operational amplifier shown in the figure. The designer wishes to realize the input resistance seen by the smallsignal source to be as large as possibl
The common emitter amplifier shown in the figure is biased using a 1 mA ideal current source. The approximate base current value is
Assume that and in figure are ideal diodes. The value of current is
The typical frequency response of a two-stage direct coupled voltage amplifier is as shown in figure
Assume that the N-channel MOSFET shown in the figure is ideal, and that its threshold voltage is +1.0 V. The voltage between nodes a and b is:
In the given figure, if the input is a sinusoidal signal, the output will appear as shown
Assume that the threshold voltage of the N-channel MOSFET shown in figure is + 0.75 V. The output characteristics of the MOSFET are also shown The voltage gain of the amplifier is
A unity feedback system, having an open loop gain , becomes stable when
A state variable system , with the initial condition and the unit step input has the state transition equation
A system with zero initial conditions has the closed loop transfer function . The system output is zero at the frequency
The gain margin of a unity feed back control system with the open loop transfer function is
If the compensated system shown in the figure has a phase margin of at the crossover frequency of 1 rad/sec, then value of the gain K is
In the G(s)H(s)-plane, the Nyquist plot of the loop transfer function G(s)H(s) = passes through the negative real axis at the point
Figure shows the root locus plot (location of poles not given) of a third order system whose open loop transfer function is
When subject to a unit step input, the closed loop control system shown in the figure will have a steady state error of
The digital circuit shown in the figure works as
In the figure, as long as = 1 and = 1, the output Q remains
Select the circuit, which will produce the given output Q for the input signals and given in the figure
If and are the inputs to the circuit shown in the figure, the output Q is
The 8085 assembly language instruction that stores the content of H and L register into the memory locations and , respectively, is:
A coil of inductance 10 H and resistance 40 is connected as shown in the figure. After the switch S has been in contact ith point 1 for a very long time, it is moved to point 2 at, t=0. For the value
Two networks are connected in cascade as shown in the figure. With usual notations the equivalent A,B,C and D constants are obtained. Given that, C = 0.025 , the value of is
For the three-phase circuit shown in the figure, the ratio of the currents : : is given by
For the two port network shown in the figure, the Z-matrix is given by
The RL circuit of the figure is fed from a constant magnitude, variable frequency sinusoidal voltage source . At 100 Hz, the R and L elements each have a voltage drop . If the frequency of the source
In the given figure, the Thevenin's equivalent pair (voltage, impedance), as seen at the terminals P-Q, is given by
The circuit shown in the figure is in steady state, when the switch is closed at t = 0. Assuming that the inductance is ideal, the current through the inductor at t = equals
In the figure given, the initial capacitor voltage is zero. The switch is closed at t = 0. The final steady-state voltage across the capacitor is
The RMS value of the voltage u(t)= 3 + 4 cos (3t) is
A digital-to-analog converter with a full-scale output voltage of 3.5 V has a resolution close to 14 mV. Its bit size is
The simultaneous application of signals x(t) and y(t) to the horizontal and vertical plates, respectively, of an oscilloscope, produces a vertical figure of 8 display. If P and Q are constants and X(t
A PMMC voltmeter is connected across a series combination of DC voltage source and AC voltage source . The meter reads
The Q-meter works on the principle of
A 1000 V DC supply has two 1-core cables as its positive and negative leads, their insulation resistances to earth are 4M and 6M , respectively, as shown in the figure. A voltmeter with resistance 50k
The set-up in the figure is used to measure resistance R. The ammeter and voltmeter resistances are 0.01 and 2000 , respectively. Their readings are 2A and 180V, respectively, giving a measured resist
Two wattmeters, which are connected to measure the total power on a three-phase system supplying a balanced load, read 10.5 kW and -2.5 kW, respectively. The total power and the power factor, respecti
A DC ammeter has a resistance of 0.1 and its current range is 0-100 A. If the range is to be extended to 0-500 A, then meter required the following shunt resistance
Which three-phase connection can be used in a transformer to introduce a phase difference of 30 between its output and corresponding input line voltages
Two magnetic poles revolve around a stationary armature carrying two coil ( ) as shown in the figure. Consider the instant when the poles are in a position as shown. Identify the correct statement reg
For an induction motor, operation at a slip , the ration of gross power output to air gap power is equal to
On the torque/speed curve of the induction motor shown in the figure, four points of operation are marked as W, X, Y and Z. Which one of them represents the operation at a slip greater than 1 ?
A 1000 kVA , 6.6 kV, 3-phase star connected cylindrical pole synchronous generator has a synchronous reactance of 20 . Neglect the armature resistance and consider operation at full load and unity pow
Determine the correctness or otherwise of the following assertion[A] and the reason[R]. Assertion [A] : Under V/f control of induction motor, the maximum value of the developed torque remains constant
In relation to the synchronous machines, which on of the following statements is false ?
Under no load condition, if the applied voltage to an induction motor is reduced from the rated voltage to half the rated value,
In a single phase induction motor driving a fan load, the reason for having a high resistance rotor is to achieve
In relation to DC machines, match the following and choose the correct combination.
A 50 kW dc shunt is loaded to draw rated armature current at any given speed. When driven (i) at half the rated speed by armature voltage control and (ii) at 1.5 times the rated speed by field control
A three-phase cage induction motor is started by direct-on-line (DOL) switching at the rated voltage. If the starting current drawn is 6 times the full load current, and the full load slip is 4%, then
The equivalent circuit of a transformer has leakage reactance and magnetizing reactance . Their magnitudes satisfy
The charge distribution in a metal-dielectric-semiconductor specimen is shown in the figure. The negative charge density decreases linearly in the semiconductor as shown. The electric field distributi
If is the electric intensity, is equal to
An electronics switch S is required to block voltage of either polarity during its OFF state as shown in the figure (a). This switch is required to conduct in only one direction its ON state as shown
An electric motor, developing a starting torque of 15 Nm, starts with a load torque of 7 Nm on its shaft. If the acceleration at start is 2 rad/ , the moment of inertia of the system must be (neglecti
A three-phase diode bridge rectifier is fed from a 400 V RMS, 50 Hz, threephase AC source. If the load is purely resistive, then peak instantaneous output voltage is equal to
The conduction loss versus device current characteristic of a power MOSFET is best approximated by
Consider a phase-controlled converter shown in the figure. The thyristor is fired at an angle in every positive half cycle of the input voltage. If the peak value of the instantaneous output voltage e
The given figure shows a step-down chopper switched at 1 kHz with a duty ratio D = 0.5. The peak-peak ripple in the load current is close to
The figure shows the voltage across a power semiconductor device and the current through the device during a switching transitions. Is the transition a turn ON transition or a turn OFF transition ? Wh
The output voltage waveform of a three-phase square-wave inverter contains
A generator with constant 1.0 p.u. terminal voltage supplies power through a step-up transformer of 0.12 p.u. reactance and a double-circuit line to an infinite bus bar as shown in the figure. The inf
An 800 kV transmission line has a maximum power transfer capacity of P. If it is operated at 400 kV with the series reactance unchanged, the new maximum power transfer capacity is approximately
The insulation strength of an EHV transmission line is mainly governed by
A load centre is at an equidistant from the two thermal generating stations and as shown in the figure. The fuel cost characteristic of the generating stations are given by Where are the generation in
The parameters of a transposed overhead transmission line are given as : Self reactance /km and Mutual reactance /km The positive sequence reactance and zero sequence reactance , respectively in /km a
The p.u. parameter for a 500 MVA machine on its own base are: inertia M = 20 p.u.; reactance X = 2 p.u. The p.u. values of inertia and reactance on 100 MVA common base, respectively, are
The network shown in the given figure has impedances in p.u. as indicated. The diagonal element of the bus admittance matrix of the network is
High Voltage DC (HVDC) transmission is mainly used for
At a 220 kV substation of a power system, it is given that the three-phase fault level is 4000 MVA and single-line to ground fault level is 5000 MVA Neglecting the resistance and the shunt suspectance
At an industrial sub-station with a 4 MW load, a capacitor of 2 MVAR is installed to maintain the load power factor at 0.97 lagging. If the capacitor goes out of service, the load power factor becomes
If u(t) is the unit step and is the unit impulse function, the inverse z-transform of F(z)= for is
The Laplace transform of a function f(t) is , f(t) approaches
The Fourier series for the function is
For the triangular wave from shown in the figure, the RMS value of the voltage is equal to