THE ONLY PREREQUISITE TO UNDERSTAND AND TO ANSWER FOLLOWING QUESTIONS IS:
A) You must know the units of the special different entities in physics (primarily LEFT side of your brain):    
i.e. magnetic flux density B in Vs/m², equivalece of energy units is Ws = Nm etc    
... if you don't know it you can learn and memorize it by studying the answers in Part 1 + 2
B) You must know the difference between a scalar and vector in physics (primarily LEFT side of your brain):
i.e. electrical voltage U (with unit V) is a scalar, electrical field strength E (with unit V/m) is a vector etc
... if you don't know it you can learn and memorize it by studying the answers in Part 1 + 2
C) You must use the right-hand-rule and the 3-finger-rule of your right hand visualizing directions of resulting vectors in physics
(primarily RIGHT side of your brain ... only focus your interest on the first two figures built by the right hand): 

IMPORTANT:  Handling with entities and following equations do not use only the LEFT side of your brain ...
... please also ACTIVATE the RIGHT side of your brain, visualizing the phenomenon of the special tasks and problems.
.