QUES: A commutator is a mechanism used to switch the input of most DC machines and certain AC machines consisting of slip ring segments insulated from each other and from the electric motor's shaft. The motor's armature current is supplied through the stationary brushes in contact with the revolving commutator, which causes required current reversal and applies power to the machine in an optimal manner as the rotor rotates from pole to pole. In absence of such current reversal, the motor would brake to a stop. In light of significant advances in the past few decades due to improved technologies in electronic controller, sensorless control, induction motor, and permanent magnet motor fields, electromechanically commutated motors are increasingly being displaced by externally commutated induction and permanent-magnet motors.

From where is current to the motor not supplied?
What is the answer?
ANS: unanswerable
QUES: Several churches and monasteries were built inside, or close to, the city of Utrecht. The most dominant of these was the Cathedral of Saint Martin, inside the old Roman fortress. The construction of the present Gothic building was begun in 1254 after an earlier romanesque construction had been badly damaged by fire. The choir and transept were finished from 1320 and were followed then by the ambitious Dom tower. The last part to be constructed was the central nave, from 1420. By that time, however, the age of the great cathedrals had come to an end and declining finances prevented the ambitious project from being finished, the construction of the central nave being suspended before the planned flying buttresses could be finished. Besides the cathedral there were four collegiate churches in Utrecht: St. Salvator's Church (demolished in the 16th century), on the Dom square, dating back to the early 8th century. Saint John (Janskerk), originating in 1040; Saint Peter, building started in 1039 and Saint Mary's church building started around 1090 (demolished in the early 19th century, cloister survives). Besides these churches the city housed St. Paul's Abbey, the 15th-century beguinage of St. Nicholas, and a 14th-century chapter house of the Teutonic Knights.

What was Utrecht built around?
What is the answer?
ANS: unanswerable
QUES: Greek art has a long and varied history. Greeks have contributed to the visual, literary and performing arts. In the West, ancient Greek art was influential in shaping the Roman and later the modern western artistic heritage. Following the Renaissance in Europe, the humanist aesthetic and the high technical standards of Greek art inspired generations of European artists. Well into the 19th century, the classical tradition derived from Greece played an important role in the art of the western world. In the East, Alexander the Great's conquests initiated several centuries of exchange between Greek, Central Asian and Indian cultures, resulting in Greco-Buddhist art, whose influence reached as far as Japan.

In the Land of the Rising Sun, what influence was of non-Greek descent ?
What is the answer?
ANS:
unanswerable