Electrical Machines Quiz

What is the main difference between an AC motor and a DC motor?

• Type of current used

• Number of wires connected

• Size of the motor

• Color of the motor casing

Explain the working principle of a synchronous motor.

• The working principle of a synchronous motor involves the use of hydraulic pressure.

• The working principle of a synchronous motor is based on the magnetic locking between the stator's rotating magnetic field and the rotor.

• A synchronous motor works based on the interaction of electric and gravitational fields.

• Synchronous motors operate by converting thermal energy into mechanical energy.

What is the function of commutator in a DC machine?

• To regulate the voltage output

• To increase the speed of the machine

• To reverse the current direction in the armature windings

• To control the temperature of the windings

Define slip in the context of an induction motor.

• Slip is the ratio of the rotor speed to the synchronous speed of the rotating magnetic field

• Slip is the speed at which the motor operates when it is turned off

• Slip is the difference between the synchronous speed of the rotating magnetic field in the stator and the actual rotor speed.

• Slip is the term used to describe the efficiency of the motor

What is the significance of back EMF in a DC motor?

• Back EMF in a DC motor causes overheating

• Back EMF in a DC motor has no effect on current draw

• Back EMF in a DC motor increases the current flow

• Back EMF in a DC motor limits the current flow and prevents excessive current draw.

Differentiate between a transformer and an electric machine.

• A transformer is used for power generation, while an electric machine is used for voltage regulation.

• A transformer converts electrical energy into mechanical energy, while an electric machine transfers energy between circuits.

• A transformer changes the frequency of the electrical energy, while an electric machine does not.

• The main difference is that a transformer transfers energy between circuits without changing the frequency, while an electric machine converts electrical energy into mechanical energy or vice versa.

What are the various losses that occur in an electrical machine?

• Voltage losses

• Magnetic losses

• Resistance losses

• Copper losses, iron losses, mechanical losses, and stray losses

Describe the construction of a three-phase induction motor.

• The bearings in a three-phase induction motor are unnecessary

• The construction of a three-phase induction motor involves a single winding in the stator

• The construction of a three-phase induction motor involves a stator with three windings, a rotor with conductive bars, and bearings to support the rotor shaft.

• A three-phase induction motor has a rotor made of plastic

What is the role of a capacitor in a single-phase induction motor?

• Increases the torque output

• Controls the speed of the motor

• Creates a phase shift between windings

• Regulates the voltage supply

Explain the concept of torque in electrical machines.

• Torque in electrical machines is the rotational force generated by current flowing in a magnetic field.

• Torque in electrical machines is the voltage output.

• Torque in electrical machines is the resistance to current flow.

• Torque in electrical machines is the speed of the motor.