Mastery ELECS 5

The number of stator field windings in an ac tachometer are: 4 2 3 1

2

Power handling capacity of wire wound potentiometer used in control systems is about: 0.1 W 100 W 25 W 5 W

5 W

Assertion (A): When the performance of a stable second order system is improved by a PID controller, the system may become unstable.Reason (R): PID controller increases the order of the system to 3. A is correct but R is wrong R is correct but A is wrong Both A and R are correct but R is not correct explanation of A Both A and R are correct and R is correct explanation of A

Both A and R are correct and R is correct explanation of A

The current wave shape shown in figure (1) is applied to a circuit element. The voltage across the element is shown in figure (2). The element is: R Semiconductor C L

C

Consider the following statements: 1. The positiveness of coefficients of characteristic equation is necessary as well as sufficient condition for stability of first and second order systems. 2. The positiveness of coefficients of characteristic equation ensures negativeness of real roots but is not sufficient condition for stability of third and higher order systems. Out of above statements: both 1 and 2 are correct both are wrong only 1 is correct only 2 is correct

both 1 and 2 are correct

In a mechanical accelerometer, the steady state displacement is a measure of: neither constant input acceleration nor constant input velocity constant input velocity either constant input acceleration or constant input velocity constant input acceleration

constant input acceleration

An RLC series circuit is underdamped. To make it overdamped, the value of R: has to be increased has to be decreased has to be increased to infinity has to be reduced to zero

has to be increased

In a synchro transmitter: input is stator voltages and output is angular position of shaft input is rotor voltage and output is angular position of rotor shaft input is angular position of rotor shaft and output is rotor voltage input is angular position of rotor shaft and output is stator voltages input is rotor voltage and output is angular position of rotor shaft

input is angular position of rotor shaft and output is stator voltages

A compensator has its pole and zero as shown in the given figure: lead compensator lag compensator lead-lag compensator series compensator

lead compensator

The pole zero plot of the given figure is for: None of the choices non-minimum phase function minimum phase function all pass function

minimum phase function

The load impedance ZL of a CE amplifier has R and L in series. The phase difference between output and input will be: 0 180° more than 180° but less than 270° more than 90° but less than 180°

more than 180° but less than 270°

In a second order system, peak overshoot is independent of: natural frequency damping factor both damping factor and natural frequency neither damping factor nor natural frequency

natural frequency

For stable network the real parts of poles and zeros of driving point functions must be: positive negative negative or zero zero

negative or zero

In a BJT circuit a pnp transistor is replaced by npn transistor. To analyze the new circuit: all calculations done earlier have to be repeated replace all calculated voltages and currents by reverse values replace all calculated currents by reverse values replace all calculated voltages by reverse values

replace all calculated voltages and currents by reverse values

Wave A = 100 sin ωt and wave B = 100 cos ωt. Then: rms values of the two waves may or may not be equal rms values of A is more than that of B rms values of the two waves are equal rms values of A is less than that of B

rms values of the two waves are equal

An amplifier has a large ac input signal. The clipping occurs on both the peaks. The output voltage will be nearly a: sine wave or triangular wave sine wave triangular wave square wave

square wave

To protect the diodes in a rectifier and capacitor input filter circuit it is necessary to use: surge inductor surge resistor both surge resistor and surge inductor surge capacitor

surge resistor

In an ac circuit, the maximum and minimum values of power factor can be: 0 and -1 1 and 0 1 and -1 2 and 0

1 and 0

Which of the following pairs are correctly matched? 1. Brune`s realization : realization with ideal transformer. 2. Cauer realization : ladder realization. 3. Bott Duffin realisation : with non ideal transformer. Select the answer using the following codes: 2 and 3 1, 2 and 3 1 and 2 1 and 3

1 and 2

The circuit in figure will act as ideal current source with respect to terminals A and B when frequency is: 1 rad/sec 4 rad/sec 0 16 rad/sec

1 rad/sec

Consider the following statements: A clamper circuit 1. adds or subtracts a dc voltage to a waveform 2. does not change the waveform 3. amplifiers the waveform Which are correct? 1, 2 1, 2, 3 2, 3 1, 3

1, 2

Study the circuit of figure and examine the following statements: 1. It is an active low pass finer. 2. It is a second order filter. 3. The change in gain is 40 dB/decade. Which of the above statements are correct? 1, 2 and 3 1 and 2 2 and 3 1 and 3

1, 2 and 3

In the signal flow graph of the given figure, the number of forward paths is: 1 4 3 2

2

In log magnitude Bode diagram the slope of high frequency asymptote of (1 + jωT) is: 20 dB per octave 10 dB per decade 20 dB per decade 10 dB per octave

20 dB per decade

For a system to work, as oscillator the total phase shift of the loop gain must be equal to: 90° 360° 270° 45°

360°

A two-branch parallel circuit has a 20 Ω resistance and 1 H inductance in one branch and a 100 μF capacitor in the second branch. It is fed from 100 V ac supply, at resonance, the input impedance of the circuit is: 500 Ω 5 Ω 20 Ω 50 Ω

500 Ω

Assertion (A): The root locus of a control system is symmetrical about real axis.Reason (R): For all polynomials with real coefficients, complex poles always occur in conjugate pairs. Both A and R are correct but R is not correct explanation of A A is correct but R is wrong R is correct but A is wrong Both A and R are correct and R is correct explanation of A

Both A and R are correct and R is correct explanation of A

Which power amplifier can deliver maximum load power? Class C Class AB Class A Class B

Class C

In figure, v₁ = 8 V and v₂ = 4 V. Which diode will conduct? Neither D₁ nor D₂ D₁ only Both D₁ and D₂ D₂ only

D₁ only

Which of the following oscillators is suitable for frequencies in the range of megahertz? Wien bridge Both RC phase shift and Hartley RC phase shift Hartley

Hartley

Assertion (A): The time response, usually, is slower with lag compensation. Reason (R): The natural undamped frequency and bandwidth are increased. Both A and R are correct but R is not correct explanation of A R is correct but A is wrong Both A and R are correct and R is correct explanation of A A is correct but R is wrong

R is correct but A is wrong

When a current source I is suddenly connected across a two terminal relaxed RC circuit at time t = 0, the voltage across the current source is shown in figure. The RC circuit is: a parallel combination of R and C a series combination of R and C a pure capacitor a series combination of R and parallel combination of R and C

a series combination of R and parallel combination of R and C

A stepper motor is essentially: either induction motor or dc motor dc motor induction motor a synchronous motor

a synchronous motor

In a CE amplifier the input impedance is equal to the ratio of: ac base voltage to ac emitter current ac base voltage to ac base current ac collector voltage to ac collector current ac emitter voltage to ac collector current

ac base voltage to ac base current

The degree of the nodes 1, 2, 3, 4 is: 2 for 1, 2, 3, and 3 for 4 2 all 3 3

all 3

The given figure shows a hybrid servosystem. The components 1, 2, 3, 4 are respectively: amplifier, demodulator, dc servomotor and load amplifier, dc servomotor, demodulator and load demodulator, amplifier, dc servomotor and load demodulator, dc servomotor, amplifier and load

amplifier, demodulator, dc servomotor and load

For a stable system having two or more gain crossover frequencies the phase margin is measured: at the gain crossover frequencies None of the choices at highest gain crossover frequency at lowest gain crossover frequency

at highest gain crossover frequency

To prevent a DC return between source and load, it is necessary to use: capacitor between source and load resistor between source and load either resistor between source and load or inductor between source and load inductor between source and load

capacitor between source and load

In force voltage analogy, displacement is analogous to: current charge voltage None of the choices

charge

A current is flowing through a conductor with non-uniform area of cross-section. Then: current will be different at different cross-sections. current will be different but current density will be same at all the cross-sections current will be the same but current density will be different at different cross-sections. current will be the same at all the cross-sections.

current will be the same but current density will be different at different cross-sections.

A forward voltage of 9 V is applied to a diode in series with a 1 kΩ load resistor. The voltage across load resistor is zero. It indicates that: diode is either short circuited or open circuited diode is open circuited resistor is open circuited diode is short circuited

diode is open circuited

The noise figure of FET circuit is: independent of all above dependent on the triggering mechanism independent of the quiescent point dependent on the quiescent point only

independent of the quiescent point

The circuit diagram shown in the figure consists of transistors in: Darlington connection cascade connection parallel connection series connection

parallel connection

The frequency at which phase angle is 180° is called: frequency of limited stability stability limit frequency phase crossover frequency gain margin frequency

phase crossover frequency

The self bias provides: large voltage gain stable Q point high input impedance high base current

stable Q point

The root locus branches: start from open loop poles and terminate at zeros None of the choices start from open loop zeros and terminate at poles may start from pole or zero and terminate at another pole or zero

start from open loop poles and terminate at zeros

In an RC series circuit R = 100 Ω and XC = 10 Ω. In this circuit: the current leads the voltage by about 84° the current leads the voltage by about 6° the current and voltage are in phase the current lags the voltage by about 6°

the current leads the voltage by about 6°

In a minimum function: the degree of numerator and denominator are equal the degree of numerator is one less than degree of denominator the degree of numerator and denominator are unequal the degree of numerator is one more than degree of denominator

the degree of numerator and denominator are equal

For a second order system, the position of poles is shown in the given figure. This system is:

underdamped

The drift velocity of electrons is: half the speed of light very small as compared to speed of light equal to speed of light almost equal to speed of light

very small as compared to speed of light