Fundamentals of Electrical and Electronic Engineering

The armature of DC motor is made up of laminated silicon steel to _____

• To reduce mass

• To reduce hysteresis loss

• To reduce eddy current loss

• To reduce both hysteresis loss and eddy current loss

The number of parallel paths in lap connected winding is equal to

• 2

• Number of poles

• greater than the number of the poles

• less than the number of poles

What will happen, with the increase in speed of a DC motor?

• Back emf increase but line current falls.

• Back emf falls and line current increase.

• Both back emf as well as line current increase.

• Both back emf as well as line current fall.

An induction motor is otherwise known as

• DC compound motor

• DC series motor

• synchronous motor

• asynchronous motor

an induction motor, rotor speed is always

• Less than the stator speed

• More than the stator speed

• Equal to the stator speed

• zero

Slip ring induction motor are employed only for

• Speed control

• High starting torque

• Both (a) and (b)

• low starting torque

The Transformer ratings are usually expressed in

• Volts

• amperes

• KVA

• KW

In which of the following reason induction motor operation is stable?

• Low Slip region

• High slip region

• medium slip region

• low speed region

The efficiency of transformer is

• Greater than DC machines

• lesser than DC machines

• equal to DC machines

• Twice the DC machines

Which of the following does not change in a transformer?

• Current

• Voltage

• Frequency

• power