W1 Quiz Basic Concept of Electrical Machine

According to Faraday's law of electromagnetic induction, an electromotive force (EMF) is induced in a conductor whenever it:

• Is placed in a static magnetic field.

• Carries a constant current

• Cuts magnetic flux.

• Is made of copper.

A conductor is moving through a uniform magnetic field. To maximize the induced EMF, the conductor should move:

• Parallel to the magnetic field lines.

• Perpendicular to the magnetic field lines.

• At a 45-degree angle to the field lines.

• In a circular path within the field.

What is the primary purpose of laminating the iron core in a transformer or electrical machine?

• To increase the magnetic flux.

• To reduce eddy current loss.

• To increase the core's mechanical strength.

• To simplify the construction process.

A simple DC motor and a simple DC generator are constructed identically. Analyze what determines whether the machine acts as a motor or a generator.

• The direction of the magnetic field.

• The number of turns in the armature winding.

• Whether the input is electrical energy or mechanical energy.

• The type of carbon brushes used.

In a purely inductive single-phase AC circuit, what is the phase relationship between the voltage and the current?

• Voltage and current are in phase.

• Voltage lags the current by 90 degrees.

• Voltage leads the current by 90 degrees.

• Voltage leads the current by 120 degrees.

A single-phase circuit supplied with 240 V AC has a load that draws 10 A. The real power consumed is 1.92 kW. Calculate the power factor.

• 1.0

• 0.9

• 0.8

• 0.7

A single-phase motor is connected to a 230 V supply. A technician measures that the voltage leads the current. What can be concluded about the load?.

• It is a purely resistive load

• It is a predominantly inductive load.

• It is a predominantly capacitive load.

• The measurement is incorrect.

A circuit contains a resistor and an unknown component. When connected to an AC source, the current lags the voltage by 30 degrees. The unknown component must be:

• A capacitor.

• A resistor.

• An inductor.

• A second power source.

Analyze the consequence of connecting a device rated for 120 V, 60 Hz to a 240 V, 60 Hz supply.

• The device will operate more efficiently.

• The device will draw half the current and work normally.

• The device will likely be damaged due to excessive current.

• The device will not turn on.

What is the standard phase displacement in degrees between any two phases in a balanced three-phase system?

• 90 degrees

• 120 degrees

• 180 degrees

• 360 degrees