<P> This value can be calculated in either a static (time - invariant) or a dynamic (varying with time) electric field at a specific time in units of joules per coulomb (JC), or volts (V). The electric potential at infinity is assumed to be zero . </P> <P> A generalized electric scalar potential is also used in electrodynamics when time - varying electromagnetic fields are present, but this cannot be so simply calculated . The electric potential and the magnetic vector potential together form a four vector, so that the two kinds of potential are mixed under Lorentz transformations . </P> <P> Classical mechanics explores concepts such as force, energy, potential etc . Force and potential energy are directly related . A net force acting on any object will cause it to accelerate . As an object moves in the direction in which the force accelerates it, its potential energy decreases: the gravitational potential energy of a cannonball at the top of a hill is greater than at the base of the hill . As it rolls downhill its potential energy decreases, being translated to motion, inertial (kinetic) energy . </P> <P> It is possible to define the potential of certain force fields so that the potential energy of an object in that field depends only on the position of the object with respect to the field . Two such force fields are the gravitational field and an electric field (in the absence of time - varying magnetic fields). Such fields must affect objects due to the intrinsic properties of the object (e.g., mass or charge) and the position of the object . </P>

What is the si unit for electric potential