Why potential energy for a test charge with negative charge on it is negative and it’s vice versa?
The electric potential Vpata point P due to a single point charge +Q is Vp=Q4πϵ0r Where r is the distance of point P from the charge +Q. VP=9×109Qr... in free space/air VP=9×109Qϵrr ... in a medium
If Q is positive, then potential at P is positive. On the other hand, if Q is negative, then potential at P is negative. It is reminded that electric potential is a scalar quantity. A positive charge loses electric potential energy as it moves from high potential to low potential and vice-versa. On the other hand, a negative charge gains electric potential energy as it moves from high to low potential and vice-versa.