In a D.C. machine the number of brush arms is _____ the number of poles.

D.C. machines designed with a large value of air gap length have

A. worst, ventilation

B. poor ventilation

C. better ventilation

D. none of the above

_________ electromagnets generally function as holding magnets.

A. Tractive

B. Portative

C. Either of the above

D. None of the above

By which of the following methods motor rating for variable load drives can be determined ?

A. Method of average losses

B. Equivalent current method

C. Equivalent torque method

D. Equivalent power method

E. All of the above

In direct cooled system using hydrogen both stator and rotor conductors are made

A. solid

B. hollow

C. perforated

D. any ofthe above