If the length of a wire is halved and the cross-sectional area is doubled, the resistance will be （）

A.both generate alternating voltages
B.both rectify the voltage before delivery
C.are constructed at the same physical size for the same kilowatt rating
D.both supply three-phase power

A.increase the field excitation
B.decrease the field excitation
C.increase the number of magnetic poles
D.increase the speed of the prime mover

A.in series with the power source and load
B.in parallel with the power source and load
C.insuring correct polarity
D.using the lowest range possible to prevent instrument damage