Zero level (physics)

In physics, the zero level describes a place or an area to which the indication of the potential energy relates. There it has the value zero by definition. This definition is necessary because the potential energy is only known up to a constant amount that can be determined arbitrarily.

Usual definitions

In the homogeneous gravitational field , the zero level is a horizontal surface, the height of which can be chosen as desired. For example, the floor, the starting height of a movement or the equilibrium position of a vibrating system can be selected as the zero level. Which choice makes sense depends on the specific problem.
In the gravitational field of a celestial body or in the Coulomb field of a point charge (e.g. of the atomic nucleus ) it is customary to set the zero level at infinity. This is possible because both the gravitational potential and the Coulomb potential converge for very great distances. Since the work that has to be done to remove a specimen from the field is always positive in these cases, the potential energy is negative.
In Geopotential forms geoid the zero level.