ELECTRICAL ENGINEERING BITS-5

301.

The solid angle subtended by an area of 2400 cm2 on the surface of a sphere of diameter 1.2 m is ______?

 2 / 3.

302.

Which of the following heating methods has maximum power factor ?
 Resistance heating 

303.

Which of the following motors has series characteristics ?
 Repulsion motor 

304.

A moving-coil permanent-magnet instrument can be used as _____ by using a low resistance shunt
 ammeter 

305.

It is required to measure the true open circuit e.m.f. of a battery. The best device is
 D.C. potentiometer 

306.

In order to achieve high accuracy, the slide wire of a potentiometer should be

 as long as possible

307.

Which of the following materials has a negative temperature co-efficient of resistance?
 Carbon 

308.

What will be the total flux emitted by a source of 60 candle power?

 754.2 lumens.

309.

For which of the following loads, armature reaction is magnetizing in nature?
 pure capacitive load 

310.

Solid angle is expressed in terms of __?
 steredians. 

311.

The friction at the track is proportional to

 speed

312.

For three-phase induction motors which of the following is the least efficient method of speed control ?
 Rheostatic control 

313.

A Weston synchronoscope is a
 dynamometer instrument 

314.

__________-has the least value of starting torque to full load torque ratio.

 Squirrel cage induction motor

315.

On increasing the thickness the furnace will drop furnace _______
 Temperature inside the outer surface of furnace walks will drop. 

316.

If the excitation is increased, the power factor is ________?

 lagging power factor

317.

Which of the following meters are not used on D.C. circuits
 Induction meters 

318.

An ammeter is a

 secondary instrument

319.

The power of a n-phase circuit can be measured by using a minimum of
 (n - 1) wattmeter elements 

320.

In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The power factor of the load was

 unity

321.

Which of the following rotor requires damper winding?
 salient pole rotor 

322.

The phase lag produced by transportation relays

 increases linearly with frequency

323.

In case of ________ free running and coasting periods are generally long.
 main-line service 

324.

_______________ is not an applictaion of dielectric heat.
 Soldering. 

325.

The rate of acceleration on suburban orurban service is in the range
 1.6 to 4.0 km phps 

326.

Copper as conductor for cables is used as
 annealed 

327.

For diesel locomotives the range of horsepower is
 1500 to 2500 

328.

Locomotives with monometer bogies have

 suitability for passanger as well as freight service

329.

In single core cables armouring is not done to

 avoid excessive sheath losses

330.

Which of the following materials is preferred for transmitting electrical energy over long distance ?

 Steel reinforced aluminium

331.

Stability of a synchronous motor ---------- with the increase in excitation.

 increases

332.

______is an element used in semiconductors whose atoms have three valence electrons.

 An acceptor

333.

The pointer of an indicating instrument should be
 very light 

334.

An ACSR conductor has internal inductance 0.05 mH/Km for µr = 1. If this ACSR is replaced with another having µr = 2, then find the internal inductance?

 0.1 mH/Km

335.

In a series circuit with unequal resistances
 the highest resistance has the highest voltage drop 

336.

For measuring current at high frequency we should use

 thermocouple instrument

337.

A dynamometer wattmeter can be used for
 both D.C. and A.C. 

338.

With rise in temperature the resistance of pure metals

 increases

339.

The use of _____ instruments is merely confined within laboratories as stand¬ardizing instruments.

 absolute

340.

A smaller air gap in a induction motor helps to __________
 reduce the magnetizing current 

341.

Synchronous condensers are used to ______?

 improve the power factor

342.

By increasing impurity content in the metal alloy the residual resistivity always

 increases

343.

The dielectric loss in a dielectric is proportional to ________

 The square of the voltage impressed on the dielectric.

344.

For some given transmission line the expression for voltage regulation is given by (Vs - Vr)/Vr *100%. Hence,

 this must be a short line

345.

An H.R.C. fuse is
 a ceramic body having metal and caps 

346.

Which of the following protects a cable against mechanical injury ?
 Armouring 

347.

The effect of error damping is to

 reduce steady state error

348.

The distance between the starts of two consecutive coils measured in terms of coil sides is called
 winding pitch 

349.

Skin effective is more in case of ?
 communication lines 

350.

The substances whfch have a large number of free electrons and offer a low resistance are called
 conductors 

351.

It is desirable to operate the arc furnaces at power factor of

 0.707 lagging

352.

Wave winding is prefered for which of the following rating?
 low current and high voltage 

353.

Which of the following is the disadvantage of electric traction over other systems of traction ?

 High capital outlay in fixed instal-lations beside route limitation

354.

The advantage of cables over overhead transmission lines is
 can be used in congested areas 

355.

Universal motors are used in _____
 food processing 

356.

________ has the best damping properties.

 Cast iron

357.

In a cable immediately above metallic sheath _____ is provided.

 bedding

358.

_______ frequency is not common in low frequency traction system
 40 Hz 

359.

The insulation of the cable decreases with
 the increase in length of the insulation 

360.

Which of the following matrix is used for load flow studies?
 Y bus matrix 

361.

________ is viscoelastic.

 rubber

362.

Can a same transformer can be used as step up and step down

 Yes

363.

Inductance of transmission line will decrease when

 GMD decrease and GMR increase

364.

Which of the following motors are preferred for overhead travelling cranes ?
 Short time rated motors 

365.

Which of the following is the advantage of electric braking ?
 It avoids wear of track 

366.

_________signal will become zero when the feedback signal and reference signs are equal.
 Actuating 

367.

A 3 Q resistor having 2 A current will dissipate the power of
 12 watts 

368.

A car is rtyining at a constant speed of 50 km/h, which of the following is the feedback element for the driver ?

 Needle of the speedometer

369.

Which of the following material is not a semiconductor ?

 Silica

370.

In open loop system
 the control action is independent of the output 

371.

Proximity effect is more in case of __________?
 power cables 

372.

Electrical machines having a power output upto about 750 W may be called_______machines.
 small size 

373.

An automatic toaster is a ______ loop control system.
 open 

374.

Which of the following statement is true both for a series and a parallel D.C. circuit?
 Power are additive 

375.

Which of the following method is used for changing power factor from leading to lagging ?

 shunt reactor

376.

The pressure coil of a wattmeter should be connected on the supply side of the current coil when

 load impedance is high

377.

In a steam locomotive electric power is provided through
 small turbo-generator 

378.

A sensitive galvanometer produces large deflection for a

 small value of current

379.

___________is not a final control element.

 Potentiometer

380.

For the transmission of heat from one body to another
 temperature of the two bodies must be different 

381.

The length cf air gap to be provided in ______ is primarily determined by power factor consideration.
 induction motor 

382.

A _____ device prevents the oscillation of the moving system and enables the latter to reach its final position quickly

 damping

383.

The value of off diagonal elements is

 which is connected between bus i and bus j with negative sign

384.

The minimum dielectric stress in a cable is at

 lead sheath

385.

_________is a closed loop system.
 Auto-pilot for an aircraft 

386.

Speed control by variation of field flux results in ______

 constant power drive.

387.

To measure radio frequency, the suitable frequency meter is
 hetrodyne frequency meter 

388.

Selenium is _____ semiconductor.
 intrinsic 

389.

The resistance of a parallel circuit consisting of two branches is 12 ohms. If the resistance of one branch is 18 ohms, what is the resistance of the other ?
 36 Q 

390.

In a Schering bridge the potential of the detector above earth potential is

 a few volts only

391.

The travelling speed of cranes varies from

 1 to 2.5 m/s

392.

In direct cooled system using hydrogen both stator and rotor conductors are made
 hollow 

393.

A motor has a thermal heating time constant of 50 mm. When the motor runs continuous of full scale, its final temperature rise is 80° C, what would be the temperature rise after 1 hour, if the motor runs continuously on full load?

 55.9 ° C.

394.

The transfer function is applicable to which of the following ?
 Linear and time-in variant systems 

395.

In an arc furnace, the choke is provide to __________

 Stabilize the arc.

396.

Which of the following statement are incorrect?
 A conductor is an equipotential body and E is always tangential to the conductor. 

397.

Armature reaction depends on which of the following?
 both of these 

398.

In 4 quadrant operation of a hoist 3rd quadrant represents

 reverse motoring.

399.

A non-dimensional number generally associated with natural convection heat transfer is

 Grashoff number

400.

The wattage rating of a ceiling fan motor will be
 50 - 150 W. 

401.

In a resistance split phase motor, what is the range of torque angle?
 25° to 30° 

402.

A pony motor is used for the starting which of the following motors ?
 Synchronous motor 

403.

The gravity controlled instrument has crowded scale because current is proportional to

 sine of deflection angle

404.

Thermal circuit breaker has

 delayed trip action

405.

Fault diverters are basically
 fast switches 

406.

In squirrel cage induction motors which of the following methods of starting cannot be used ?
 Resistance in rotor circuit 

407.

Which single phase motor is used for a refrigerator?

 Split phase.

408.

The rating of a fuse wire is always expressed in
 amperes 

409.

A 4 pole 50 Hz 1-phase induction motor is running at 1470 rpm. Find the forward and backward slips?

 0.02, 1.98

410.

The forbidden gap in an insulator is
 large