Electrical subjects Mini mock test

1➤ For a parallel RLC resonant circuit with resistance in series with inductor. what will be the effect on resonant frequency, if we increase the value of resistance

Resonant frequency will remainEffect cannot be estimatedResonant frequency will decreaseResonant frequency will increase

2➤ The transmission capacity of the line at 50 Hz frequency compared to 60 Hz frequency

is halfis twiceincreasesdecreases

3➤ Super tension cables are generally used up to ______ kV..

132116633

4➤ Magnetising force which is necessary to neutralise completely the magnetism is an electromagnet after the value of magnetising force becomes zero. The given statement is true for:

coercive forcemagnetic hysteresisabsolute permeability ductility

5➤ Which of the following is NOT one of the analog to digital (A/D) conversion techniques?

Voltage to frequency conversion methodSingle slope integration method Successive approximation methodVoltage to-time conversion method

6➤ n a 3 core cable, the capacitance between two conductors (with sheath earthed) is 3mF. The capacitance per phase is

9.0 µF1.5 µF6.0 µF 3.0 µF

7➤ An appropriate value of shielding angle for HV lines is Ans

30°20°60°15°

8➤ Over conventional electromechanical relays, the transistor relays have the limitations of

Reliability depending upon the large number of small components and their electrical connectionsCharacteristics varying with temperature and ageingLow short-time overload capacityAll of the options

9➤ A solar cell produces the short circuit current or open circuit voltage as Sun radiations fall on it because

Carrier recombination takes place near the junctionMajority carrier flows across the junctionDepletion layer gets reducedMinority carrier flows across the junction

10➤ _______ is NOT included in battery charging system.

InverterGeneratorRectifiercontainer for the batteries

11➤ Which of the following is NOT one of the advantages of the combined cycle, i.e. 'combined gas turbine and diesel power plants'?

More suitable for rapid start and shut down.It gives high ratio of power output to occupied ground spaceLess cooling water requirementThe combined system offers forced manual feature

12➤ The insulator used on the 11 kV lines are mainly

Pin insulatorsBoth Suspension insulators and Pin insulatorsSuspension insulatorsNone of the options

13➤ Three equal resistance of 6 ohms are connected in delta , the equivalent star value in ohms will be

222123

14➤ A device UJT internally has

One junctionTwo junctionsFour junctionsThree junctions

15➤ While making the choice of drive, which of the following factors is NOT considered?

Space availableCostSpeed of driving and driven machinesDrive machine temperature

16➤ Which of the following is the disadvantage of 'flux control method' (one of the speed control methods) of a DC shunt motor?.

As the field current is small the size of the rheostat required is smallIt provides slightly complex control.The speed control below normal rated speed is not possiblePower loss in the external resistance is very high.

17➤ 0°/180° connection can also be defined as ___________.

Star/Delta connectionStar/Star connection Delta/Star connectionIndirect-star connection

18➤ The layout of a modern steam power plant does NOT comprise of which of the following circuits?

Coal and ash circuitWater exit and flow circuitCooling water circuitAir and gas circuit

19➤ The method of neutral grounding affects the

Negative sequence networksAll type of networksZero sequence networksPositive sequence networks

20➤ When fault occurs in HV transmission lines, first the .

Relay operates then CBRelay operates then isolator then CBIsolator operates then relay then CB CB operates then the relay

21➤ Which of the following is NOT a disadvantage of HVDC transmission system?

Reactive power cannot be transmitted through a DC line. Voltage cannot be stepped upThe short circuit current required is high when compared to AC systems.Ripples and harmonics are generated when AC is converted into DC.

22➤ Which of the following is NOT the correct preventive measures to be applied for homes? .

Allow only qualified persons to attend to your electrical repairs.Use switches of the correct current ratingEnsure pins of your plugs are loose enough for proper insertingProvide proper earthing for the building/house

23➤ Silicon Controlled Rectifier (SCR) is not made up of Germanium because

Not easily available compare to SiliconIt has more leakage currentMaximum voltage handling capacity is less Maximum current is low

24➤ In which of the following are choppers NOT used?

Battery charging purposesElectric tractionAC voltage regulatorsMine haulers

25➤ In protection system which of the following type of distance relay is not affected by fault arc resistance

ReactanceImpedanceMhoDifferential

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