Chapter 2 · MCQ Read Mode

Electrical Machines

Flux linkage of a coil with N turns and flux Φ is given by:

The energy stored in the magnetic field of an inductor carrying current I is:

Ferromagnetic materials are characterized by:

Hysteresis loss in a magnetic material is represented by:

Retentivity of a magnetic material refers to:

Faraday's law of electromagnetic induction states that induced EMF is proportional to:

Lenz's law determines the:

A dynamically induced EMF (e=Blv) arises due to:

A statically induced EMF is best exemplified by:

The force on a current-carrying conductor in a magnetic field, F=BIl, is the basis of:

In a shell-type transformer, the core:

The conservator tank in a transformer is used to:

The breather in a transformer primarily functions to:

The open-circuit (no-load) test on a transformer is used to determine:

The short-circuit test on a transformer is used to determine:

Core (iron) loss in a transformer is essentially:

Maximum efficiency of a transformer occurs at the load where:

Eddy current loss in a transformer core is minimized by:

For successful parallel operation of two transformers, it is essential that they have:

Transformer capacity (rating) is expressed in:

The commutator in a DC machine primarily functions to:

A series DC motor is characterized by:

A shunt DC motor is characterized by:

Armature reaction in a DC machine refers to:

Sparking at the brushes due to armature reaction is commonly corrected using:

A starter is required when starting a DC motor mainly because:

Field control of a DC motor's speed operates by:

Armature (rheostatic) speed control of a DC motor gives speeds that are:

Maximum efficiency of a DC machine occurs when:

Which type of DC motor combines both series and shunt field windings?

In a synchronous machine, the field winding is typically excited by:

A salient-pole rotor construction is typically used for:

A brushless excitation system eliminates the need for:

The relationship between frequency, poles, and synchronous speed is given by:

The per-phase induced EMF equation for an alternator is given by:

Voltage regulation of an alternator is defined as the percentage change in terminal voltage when:

Before connecting (synchronizing) an alternator to the grid, which quantities must be matched?

For an alternator connected to an infinite bus, increasing the prime-mover's mechanical input primarily changes the machine's:

A synchronous motor, from standstill, develops:

An over-excited synchronous motor running unloaded, used for power factor correction, is called a:

A squirrel cage rotor is characterized by:

The rotating magnetic field in a three-phase induction motor is produced by:

Slip of an induction motor is defined as:

An induction motor can never run at exactly synchronous speed under load because:

Increasing rotor resistance in a slip-ring induction motor primarily: magnitude

Star-delta starting of an induction motor is used primarily to:

The blocked-rotor test on an induction motor is analogous to which transformer test?

The no-load test on an induction motor primarily determines:

The most widely used modern method for continuous, wide-range speed control of induction motors is:

Rotor resistance speed control is applicable to which type of induction motor?

A single-phase stator winding alone produces a magnetic field that is:

A single-phase induction motor, without any starting mechanism, has:

Once a single-phase induction motor is started (given an initial push), it continues to run because:

In a split-phase (resistance-start) motor, the auxiliary winding is designed with:

The auxiliary winding of a split-phase motor is typically disconnected once the motor reaches speed by:

A capacitor-start motor, compared to a plain split-phase motor, generally provides:

A shaded-pole motor achieves self-starting by:

Shaded-pole motors are typically used for:

Speed control of small single-phase induction motors (e.g. fans) is most commonly achieved by:

Which single-phase motor type generally provides the highest starting torque?