Surprise Quiz-1 on DC Machines

Which part of a DC machine converts mechanical energy into electrical energy?

• Field winding

• Brush

• Armature

• Commutator

The function of a commutator in a DC machine is to_____________.

• generate AC voltage

• convert AC to DC

• reduce eddy current losses

• maintain unidirectional current

In a DC generator___________ is used to select the direction of induced emf.

• Fleming's right-hand rule

• Fleming's left-hand rule

• Lenz's law

• Faraday's law

Which of the following types of DC generators has the field winding in series with the armature?

• Series generator

• Shunt generator

• compound generator

• separately excited generator

In a DC motor, back EMF is proportional to____________.

• armature current

• square of speed

• speed of the motor

• supply voltage

Which component in a DC machine is responsible for producing the magnetic field?

• Armature

• Field winding

• Commutator

• Shaft

In a DC motor, if the load increases suddenly, the speed______________.

• increases

• decreases

• remains constant

• becomes zero

The efficiency of a DC machine is maximum when__________.

• variable losses = constant losses

• iron losses are zero

• copper losses are minimum

• armature current is maximum

Which loss occurs due to magnetic hysteresis in the core of a DC machine?

• Copper loss

• Hysteresis loss

• Eddy current loss

• Mechanical loss

The type of DC motor used in electric traction applications is usually_______.

• shunt motor

• series motor

• compound motor

• universal motor