Reduction in core losses and increase in permeability are obtained with transformer employing

Substances which have permeability less than the permeability of free space are known as

A

Ferromagnetic

B

Paramagnetic

C

Diamagnetic

D

Bipolar

Inductance is indirectly proportional to the square of the number of turns, the permeability, and the cross-sectional area of the core.

A

True

B

False

The permeability of a core material is an indication of the ability of the material to establish a magnetic field.

A

True

B

False

The power input to an induction motor is 50 kW when it is running at 4% slip. If the stator resistance and core losses are neglected, the rotor copper loss is

A

30 kW

B

20 kW

C

2 kW

D

4 kW

Which of the following losses are significantly reduced by laminating the core of a D.C. generator?

A

Hysteresis losses

B

Eddy current losses

C

Copper losses

D

Windage losses

A laminated iron core has reduced eddy-current losses because

A

More wire can be used with less D.C. resistance in coil

B

The laminations are insulated from each other

C

The magnetic flux is concentrated in the air gap of the core

D

The laminations are stacked vertically

Which of the following losses is not dissipated by the stator core surface in a synchronous motor ?

A

Eddy current losses in the conductors

B

Iron losses in the stator

C

Copper losses in the slot portion of the conductors

D

Windage losses

Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is

A

Approximately equal to one

B

Less than one

C

Great than one

D

Cannot be found

In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are

A

friction and windage losses

B

copper losses

C

hysteresis and eddy current losses

D

none of the above

The total number obtained by a student in Physics, Chemistry and Mathematics together is 120 more than the marks obtained by him in Chemistry. What is the average mark obtained by him in Physics and Mathematics together?

A

40

B

60

C

120

D

Cannot be determined

Reduction in core losses and increase in permeability are obtained with transformer employing

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