What must be true of the direction of the current in the electromagnets of a dc motor? it needs to be perpendicular. it needs to be parallel. it needs to be switched repeatedly. it needs to stay the same.

Two large, flat, horizontally oriented plates are parallel to each other, a distance d apart. half way betwween the two plates the electric field has magnitude e. if the separation of the plates is reduced to d/2 what is the magnitude of the electric field half way between the plates?

Identify the theory that can be used to explain each phenomenon. answers diffraction: wave theory interference: wave theory reflection: both particle and wave theories refraction: both particle and wave theories

You are given a vector a = 125i and an unknown vector b that is perpendicular to a. the cross-product of these two vectors is a × b = 98k. what is the y-component of vector b?