A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The external resistance to be added in the armature circuit to limit the armature current to 125% of its rated value is

Electrical Machines
A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The external resistance to be added in the armature circuit to limit the armature current to 125% of its rated value is

15.1 Ω

31.1 Ω

31.9 Ω

15.9 Ω

15.1 Ω

31.1 Ω

31.9 Ω

15.9 Ω

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Electrical Machines
Which of the following load normally needs starting torque more than rated torque?

Air compressors.

Conveyers.

Blowers.

Centrifugal pumps.

Air compressors.

Conveyers.

Blowers.

Centrifugal pumps.

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Electrical Machines
Induction motors normally use cast aluminium rotor because aluminium is

lighter in weight.

easy to cast owing to its low melting point and is easily available.

cheaper in cost.

of low resistivity.

lighter in weight.

easy to cast owing to its low melting point and is easily available.

cheaper in cost.

of low resistivity.

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Electrical Machines
The armature of a DC motor is laminated to reduce

eddy current loss.

friction and windage loss.

copper loss.

hysteresis loss.

eddy current loss.

friction and windage loss.

copper loss.

hysteresis loss.

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Electrical Machines
If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated)

changes to three times the original value

remain the same as the original

changes to 1.5 times the original value

changes to 0.5 times the original value

changes to three times the original value

remain the same as the original

changes to 1.5 times the original value

changes to 0.5 times the original value

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Electrical Machines
The size of inter poles is small as compared to main poles. What is the reason?

In order to get more flux.

In order to get saturated.

All of these

In order to not to get saturated.

In order to get more flux.

In order to get saturated.

All of these

In order to not to get saturated.

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Electrical Machines

Electrical Machines Which of the following load normally needs starting torque more than rated torque?

Electrical Machines Induction motors normally use cast aluminium rotor because aluminium is

Electrical Machines The armature of a DC motor is laminated to reduce

Electrical Machines If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated)

Electrical Machines The size of inter poles is small as compared to main poles. What is the reason?

Electrical Machines
Which of the following load normally needs starting torque more than rated torque?

Electrical Machines
Induction motors normally use cast aluminium rotor because aluminium is

Electrical Machines
The armature of a DC motor is laminated to reduce

Electrical Machines
If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated)

Electrical Machines
The size of inter poles is small as compared to main poles. What is the reason?