All Free Electrical Engineering MCQs with Answers

• A. multiplication of front and back pitches
• B. division of front pitch by back pitch
• C. sum of front and back pitches
• D. difference of front and back pitches

Explanation: In a simplex lap winding, the resultant pitch equals the difference between the back pitch and front pitch, with the sign depending on the…

• A. to reduce the reluctance of the mag¬netic path
• B. to spread out the flux to achieve uniform flux density
• C. to support the field coil
• D. to discharge all the above functions

Explanation: Pole shoes reduce magnetic reluctance, spread flux over the armature for a more uniform flux density, and provide mechanical support for…

• A. neutralising residual magnetism
• B. creating residual magnetism by a D.C. source
• C. making the magnetic losses of forces parallel
• D. increasing flux density by adding extra turns of windings on poles

Explanation: Flashing the field means applying an external DC supply to the field winding so that residual magnetism is restored or strengthened.

• A. rotary converter
• B. mercury are rectifier
• C. induction motor D.C. generator set
• D. synchronous motor D.C. generator set

Explanation: An induction-motor-driven DC generator set provides a convenient, controllable DC supply for a DC machines laboratory.

• A. number of armature coils
• B. number of armature coil sides
• C. number of armature conductors
• D. number of armature turns

Explanation: Each armature coil is connected to one commutator segment pair or segment connection, so the number of commutator segments corresponds to…

• A. lap winding
• B. wave winding
• C. delta winding
• D. duplex wave winding

Explanation: A welding generator must deliver high current at low voltage, so it uses a lap winding with multiple parallel paths.

• A. wave wound
• B. lap wound
• C. delta wound
• D. duplex wound

Explanation: Equalizer rings are used with lap windings to equalize the voltages of parallel paths and prevent circulating currents caused by unequal…

• A. to avoid sudden loading of the primemover
• B. to avoid mechanicaljerk to the shaft
• C. to avoid burning of switch contacts
• D. all above

Explanation: A generator is connected to or removed from busbars under floating, or no-load, conditions to prevent sudden prime-mover loading, shaft…

• A. crossmagnetising
• B. demagnetising
• C. magnetising
• D. none of above

Explanation: For an unsaturated machine, the armature-reaction flux mainly acts at right angles to the main field and distorts it, so it is…

• A. demagnetisation only
• B. cross magnetisation as well as mag¬netisation
• C. crossmagnetisation as well as demagnetising
• D. cross magnetisation only

Explanation: Moving the brushes away from the geometrical neutral axis tilts the armature-reaction axis, resolving it into both a cross-magnetising…

• A. lie under south pole
• B. lie under north pole
• C. lie under interpolar region
• D. are farthest from the poles

Explanation: Commutation occurs while a coil is short-circuited by a brush, and the corresponding conductors lie in the interpolar or neutral region…

• A. graphite
• B. paper
• C. mica
• D. insulating varnish

Explanation: Mica is used between commutator segments because it has high dielectric strength, good mechanical stability, and withstands the heat and…

• A. mica
• B. copper
• C. cast iron
• D. carbon

Explanation: Carbon is commonly used for DC-machine brushes because it provides suitable electrical contact while limiting commutator wear and reducing…

• A. 4
• B. 8
• C. 16
• D. 32

Explanation: Sixteen coils in a two-layer winding provide 32 active conductors. Pole pitch is the number of conductors per pole, so it is 32 divided by…

• A. Blv
• B. Blv2
• C. Bl2v
• D. Bl2v2

Explanation: For a conductor of effective length l moving at velocity v through flux density B, the motional emf is e = Blv when the motion is…

• A. imperfect brush contact
• B. field resistance less than the critical resistance
• C. no residual magnetism in the generator
• D. faulty shunt connections tending to reduce the residual magnetism

Explanation: A shunt generator builds up when its field resistance is below the critical resistance, so that option supports voltage build-up rather…

• A. carbon
• B. soft copper
• C. hard copper
• D. all of above

Explanation: Carbon or graphite brushes are the usual choice because they provide suitable conductivity while limiting commutator wear and sparking.

• A. commutator
• B. solid connection
• C. slip rings
• D. none of above

Explanation: The armature generates alternating emf, and the commutator mechanically rectifies it so that current delivered to the external circuit is…

• A. speed
• B. load
• C. voltage
• D. speed and voltage

Explanation: Iron losses are mainly set by flux density and frequency, which are approximately constant in a D.C.

• A. reduce the bulk
• B. provide the bulk
• C. insulate the core
• D. reduce eddy current loss

Explanation: Laminating the armature core breaks up circulating paths for induced currents, greatly reducing eddy-current loss.