We know that formula of electric potential is kq/r.So in case of positive charge q is positive so electric potential is high than negative charges. Am I right?.And also in case of battery,positive terminal has high potential than negative terminal,Or part of conductor connected with positive terminal of battery has high potential and part of conductor connected with negative terminal has low potential.WHY?
Convention. We could have also defined the negative terminal to be "high potential." However, that convention has to be consistent. The positive terminal is at the high potential, and that potential causes positive charges to flow from high potential to low potential. If we had defined the convention in the other direction, then the negative terminal would be the high potential, and that potential would cause negative charges to flow from high potential to low potential.
As it turns out, in reality, the charges that flow are the negative ones. It would have been "better" to define electrons to have a positive charge and flip the terminals of the battery. Much confusion in semiconductor physics arises from the reality that electrons move from low potentials to high potentials instead of the other way around.
We can blame Ben Franklin for that. When he experimented with electricity, he needed to pick a convention. He had no way at the time of knowing which charge carrier was actually moving. He effectively flipped a coin. Sadly, he chose the less convenient convention. By the time we figured out that electrons are the charge carrier that moves, it was too late to undo all of the years of convention.