How do i calculate average velocity

Average velocity has two parts:  Its magnitude (size) and its direction.

Its magnitude is

(straight-line distance between start-point and end-point, regardless of the route that's actually followed from start to finish) divided by (time taken to travel from start to finish).

Its direction is

(direction from start-point to end-point)

Notice that straight from this definition, the average velocity of going around a full circle is zero, no matter how fast you traveled.  That's because the size of the  average velocity is calculated from the straight-line distance from start-point to end-point, and that's zero if you finish at the same point you started from.

what type of charge does it have? negative

e

explanation:

there is no change in the electric potential energy as it is in rest on both conditions.