Which part of a DC machine houses the field winding?

• Armature

• Stator

• Commutator

• Rotor

The primary role of a commutator in a DC generator is to:

• Maintain a constant current

• Convert AC to DC

• Improve efficiency

• Control voltage

What is the main purpose of interpoles in DC machines?

• Reduce armature reaction

• Increase efficiency

• Reduce losses

• Provide insulation

The efficiency of a transformer at full load is typically:

• 70-75%

• 80-85%

• 95-98%

• 50-55%

In a DC motor, back EMF is generated in:

• Field winding

• Armature winding

• Rotor core

• Commutator

The synchronous speed of a 4-pole induction motor supplied with 50 Hz is:

• 750 RPM

• 1500 RPM

• 3000 RPM

• 1000 RPM

What type of DC generator is commonly used for arc welding?

• Series generator

• Shunt generator

• Compound generator

• Permanent magnet generator

A squirrel-cage rotor is commonly used in:

• DC motors

• Synchronous motors

• Induction motors

• Stepper motors

In a transformer, the no-load current:

• Lags the applied voltage by nearly 90°

• Leads the applied voltage by nearly 90°

• Is in phase with the voltage

• Opposes the voltage

The main advantage of a 3-phase induction motor over a single-phase motor is:

• Higher efficiency

• Simpler construction

• Self-starting capability

• Lower cost