In equations (2) and (3), the quantity B is the vector representing the magnetic field. The vector qv points in the direction of v if q is positive and in the opposite direction is q is negative.
Graphically, magnetic fields are represented by arrows. Fields going into and out of the page can be represented by
When a charge enters a uniform magnetic field that is perpendicular to the direction of motion of the charge, the resulting path of the charge is circular. Since the charge is moving in a circle, its velocity is changing, and it therefore has non-zero
