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Dc machine
1-Dont try to cram or spend more time here just read it fast and cover syllabus then practice MCQ's cheptor of same topic to check your progress. . |
2-Wrong options are also given but dont concentrate there, Right answer is in bold format. |
Q41 ⇒ The sparking at brushes may occur due to trouble in commutator [other wrong options] [Discuss in forum] trouble in brushes trouble in armature excessive load. any of the above causes |
Q42 ⇒ The developed electromagnetic force and/or torque in electromechanical
energy conversion system act in a direction that tends to decrease the stored energy at constant flux. [other wrong options] [Discuss in forum] to increase the stored energy at constant flux, to decrease the coenergy at constant mmf, to deciase the stored energy at constant mmf. |
Q43 ⇒ In an electromechanical energy conversion device, the developed
torque depends upon stator field and rotor field strengths and the torque angle. [other wrong options] [Discuss in forum] stator field strength and torque angle stator field and rotor field strengths stator field strength only |
Q44 ⇒ A rotating electrical machine having its self inductances of both
the stator and the rotor windrngs, independent of rotor positïon
will definitely not develop synchronising torque. [other wrong options] [Discuss in forum] starting torque. hysteresis torque. reluctance torque |
Q45 ⇒ EMF induced in 11 coil rotating in auniform magnetic field will be
maximum when the rate of change of flux linkage is maximum [other wrong options] [Discuss in forum] flux linking with the coil is maximum. rate uf change of flux linkage is minimum rate of cutting flux by the coil sides is minimum |
Q46 ⇒ The principle of dynamically induced emf is utilised in generator. [other wrong options] [Discuss in forum] transformer, choke. thermocouple. |
Q47 ⇒ Laminated yoke in dc motor can reduce iron loss. [other wrong options] [Discuss in forum] speed regulation temperature rise sparking on load. |
Q48 ⇒ Armature of a dc machine is made of silicon steel, [other wrong options] [Discuss in forum] conducting material. insulating material non-ferrous material. |
Q49 ⇒ The armature of a dc machine is made of silicon steel laminations
to reduce both hysteresis and eddy current loss. [other wrong options] [Discuss in forum] reduce hysteresis loss only. reduce the eddy current loss only increase the permeability. |
Q50 ⇒ in a dc machine, the brushes are physically placed in the. polar axis and electrically connected to the coils lying in the interpolar axis [other wrong options] [Discuss in forum] polar axis electrically connected to the coils lying in the polar
axis. interpolar axis and electrically connected to the coils lying in polar axis. interpolar axis and electrically connected to the coils lying in inter polar axis. |
Q51 ⇒ If two 8-pole dc machines of identical armatures are wound, one
with lap winding and the other with wave winding, then wave wound machine will have more rated voltage and less current. [other wrong options] [Discuss in forum] wave wound machine will have more rated current and more
voltage lap would machine will have more rated voltage and more entrent, lap wound machine will have more rated voltage and less currcnt, |
Q52 ⇒ Welding generator will have lap winding [other wrong options] [Discuss in forum] wave winding either lap or wave winding none of these |
Q53 ⇒ Width of a carbon brush should be equal to the width of 2 to 3 commutator segments [other wrong options] [Discuss in forum] less than the width of one commutator segment. the width of ito 2 commutator segments. the width of more than 3 commutator segments |
Q54 ⇒ The dummy coils in dc machines are useful to maintain mechanical balance of armature [other wrong options] [Discuss in forum] increase the efficiency. improve the commutation. reduce the cost of the machine. |
Q55 ⇒ The coil span may or may not be exactly equal to pole pitch. [other wrong options] [Discuss in forum] must be exactly equal to pole pitch. can never be equal to pole pitch. none of the above. |
Q56 ⇒ For both lap and wave windins, there are as many commutator
bars as the number of winding elements. [other wrong options] [Discuss in forum] armature conductors poles. slots. |
Q57 ⇒ Aluminium is not used as winding wire in dc machine armature as
it requires large winding space [other wrong options] [Discuss in forum] is costlier is of low resistivity is of lower thermal conductivity |
Q58 ⇒ A frog-leg winding is used in a dc machine to eliminate the use of equalizers in lap winding. [other wrong options] [Discuss in forum] the use of compensating winding the use of compensating winding. reactance voltage produced due to commutation |
Q59 ⇒ A 4-pole lap wound dc generator has a developed power of P
watts and voltage of E volts. The adjacent brushes of the machine
are removed as they are worn out. if the machine operates with the remaining brushes, the developed voltage and power that can be
obtained from the machine are E, P/2 [other wrong options] [Discuss in forum] E, P E/2, P/2 E, P/4 |
Q60 ⇒ Approximate physical size of the 50 KW, 1800 rpm dynamo is a
function of a 25 kW, 900 rpm dynamo will be 1 [other wrong options] [Discuss in forum] 1/2 1/4 none of the above |
Or |