EE&I QUIZ. The basic function of a transformer is to change A the level of the voltage. B the power level. C the power factor. D the frequency.

EE&I QUIZ

 The basic function of a transformer is to changeA the level of the voltage.B the power level.C the power factor.D the frequency.

 Transformer is usedA to step up the voltage.B to step down the voltageC on dc.D to step up or step down the voltage.

 An auto-transformer hasA one winding with taps taken outB two interlaced windings.C two windings of same wire.D two windings of different materials.E one winding without taps.

The efficiency of a power transformer is aroundA 50%B 60%C 80%D 95%

Transformer action requires aA constant magnetic flux.B increasing magnetic flux.C alternating magnetic flux.D alternating electric flux.

In a transformer operating at constant voltage, if the input frequency increases, the core loss

A increases.B decreasesC remains constant.D increases as square of the frequency

The wattage rating for a ceiling motor will be in the range

A 50 to 250W.B 250 to 500W.C 50 to 150W.D 10 to 20W

If a dc series motor is operated on ac supply, itA will not start at allB will start and run but will have poor

performance such as excessive sparking, poor efficiency and poor power factor

C will get damaged due to burning of its windings.

D will run at excessively high speed.

A distribution transformer is selected on the basis of

A voltage regulation.B efficiency.C all day efficiency.D none of these.

The function of oil in a transformer isA to provide insulation and cooling.B to provide protection against lightning.C to provide protection against short-

circuit.D to provide lubrication.

Torque development in a dc motor depends on:A Magnetic field and radius of armatureB Current flowing through the armature

conductorsC Active length of the conductors and

number of armature conductorsD All the above

A dc motor having full load speed of 750 rpm and speed regulation of 10% will have no load speed of:

A 825 rpmB 675 rpmC 800 rpmD 700 rpm

A DC shunt motor is running at light load, what happens if the field winding gets opened?

A Motor will stopB Motor will burnC Motor will make noiseD Motor will pickup high speed

In an electrical motor, the electromagnetic torque developed is:

A In opposite direction to both load torque and fractional torque

B In the same direction to the load torque but opposite direction to the fractional torque

C In the same direction as the load torque and fractional torque

D In the same direction as the fractional torque but in opposite direction to the load torque

The starting torque of dc shunt motor is:A ZeroB LowC HighD Very high

A DC shunt motor may have rising speed-torque characteristics due to:

A Very high armature circuit resistanceB Very high field circuit resistanceC Very high demagnetizing armature

resistanceD Very low demagnetizing armature reaction

The dc motor, that has poorest speed regulation is

A Cumulative compoundB Differential compoundC SeriesD Shunt

If the supply voltage to a dc shunt motor is increased by 15%, which of the following will reduce?

A Full load currentB Full load speedC Starting torqueD None of the above

The speed of dc shunt motor can be increased above its normal speed by:

A Increasing the field currentB Decreasing the field currentC Decreasing the terminal voltageD Increasing the armature resistance

By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?

A FrameB ShaftC CommutatorD Stator

A D.C. series motor is that whichA has its field winding consisting of thick

wire and less turnsB has a poor torqueC can be started easily without loadD has almost constant speed

When two D.C. series motors are connected in parallel, the resultant speed is

A more than the normal speedB loss than the normal speedC normal speedD zero

If a D.C. motor is to be selected for conveyors, which motor would be preferred ?

A Series motorB Shunt motorC Differentially compound motorD Cumulative compound motor

Which D.C. motor is preferred for elevators ?A Shunt motorB Series motorC Differential compound motorD Cumulative compound motor

What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?

A The motor will stopB The motor will continue to runC The armature may burnD The motor will run noisy