Important Electrical MCQ

1➤ As per Barkhausen criterion for oscillation, the magnitude of the loop gain βA must be:

Equal to 1 Less than 1Greater than 1Equal to 1.5

2➤ Transient stability of a power system can be improved

by reducing transfer reactance of the systemusing high speed excitationby increasing system voltage all the above

3➤ or stability and economic reasons transmission lines are operated with the power angle in the range- A. B. C. D.

60° to 75° 30° to 45° 10° to 25°65° to 80°

4➤ he pinch off voltage for a n-channel JFET is 4 V, when VGS = 1V, the pinch-off occurs at VDS equal to:

4 V5V3V1 V

5➤ Which of the following statement is incorrect regarding MOSFET?

MOSFET has lower switching losses but higher conduction lossesMOSFET is a voltage controlled deviceMOSFET has positive temperature coefficient of resistanceSecondary breakdown occurs in MOSFET

6➤ Which of the following logic gates can be used to implement the functionality of any logic gate?

XNORXORNANDAND

7➤ Why an IGBT is also referred as a bipolar-mode MOSFET?

It comprises of two stable modes of operationIt is a combination of both types of MOSFET, enhancement type and depletion typeIt is a combination of BJT and MOSFETAll of the above

8➤ If the length of a cable is doubled, its capacitance

Becomes one-halfBecomes doubleBecomes one-fourth Remains unchanged

9➤ Electric flux , is a ______ field, and its density D, is a ______field.

Scalar and vectorVector and scalarScalar and scalar Vector and vector

10➤ Which of the following type of measuring instruments is used in the measurement of ac quantity only?

Repulsion moving-iron typePermanent-magnet moving coil typeSplit-phase induction typeHot-wire type

11➤ The demand of average load to maximum demand in power system is defined as:.

Load factorUtilization factorDemand factorAverage load

12➤ Marginally stable systems have closed loop transfer functions with only imaginary axis poles of multiplicity:

4321

13➤ RTD stands for:

Resistance Transfer DeflectorResistance Temperature DeflectorResistance Temperature DetectorResistance Transfer Detector

14➤ Which of following devices exhibits negative resistance region?

Tunnel diodeZener diode P-N junction diodeBJT

15➤ 10 V power supply would use filter capacitor of following type:

Electrolytic capacitorPaper capacitorAir capacitorMica capacitor

16➤ Which of the following is not true with respect to dielectric strength? .

It decreases with increase in humidity It increases with increase in frequency. It decreases with increase in operating temperature It decreases with increase in frequency

17➤ The transformer utilisation factor of a full wave rectifier is:

0.3690.9360.6930.5

18➤ For a load bus of a power system, the specified quantities are:

the bus voltage magnitude and its phase anglethe real reactive of power and its phase anglethe reactive component of power and its phase anglethe real and reactive components of power

19➤ A cycloconverter is a __________frequency changer.

four-stagetwo-stageone-stagethree-stage

20➤ Cycloconverters used in aircraft power supplies provide ___________ frequency power from a _______ input frequency power.

variable; variablefixed; variablevariable; fixedfixed; fixed

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