【单选题】The direction of rotation of an induction motor is ________.
A.
opposite the rotating field direction
B.
the same as the direction of the rotating field
C.
determined by the number of poles
D.
determined by the staggering of the brushes
【单选题】An electron moves in the negative x direction, through a uniform magnetic field in the negative y direction. The magnetic force on the electron is:
A.
in the positive z direction
B.
in the negative z direction
C.
in the positive y direction
D.
in the negative x direction
【简答题】Flying in a westward direction will
【多选题】The direction indices represent
A.
The connecting line between any two points within a crystal.
B.
The parallel, codirectional crystallographic direction of a crystal.
C.
The connecting line between vertex.
D.
The direction and distance between atoms.
【单选题】患者,女性,13岁,要求矫治“虎牙”。检查:磨牙中性关系,上牙弓拥挤9mm,下牙弓拥挤7mm,前牙覆(牙合)覆盖II度,直面型,下颌均角。此患者最佳治疗方案为