Read about gravitational potential in the right column before looking at the exercises.
The simulation contains two stars. The mass and radius of the second star are so small that in practice there is only one star.
The gravitational potential in a point P is defined by the work W done by the gravitational forces on a small mass m
when it is moved from infinity to P. The gravitational potential in P is then W/m. The potential is zero infinitely far from all bodies.
At the distance r from the center of a homogeneous sphere with mass M the potential is .
The graph below shows the gravitational potential near the earth neglecting all other bodies (the moon, the sun, ...).
An equipotential surface is a surface where the potential has the same value everywhere on the surface.
If the gravitational field is created by only one body the equipotential surfaces are spherical.
In a plane the equipotential surfaces appear as equipotential lines.
Orbit Xplorer can draw equipotential lines in the xy-plane when all bodies are confined to this plane. The equipotential lines are drawn with a constant potential difference between neighboring lines. They are like contour lines on a map which trace lines of equal altitude.
Electric potential can be defined in a similar way. The electric potential in a point P is W/q, where W is the work done by the electric forces moving
a small charge q from infinity to P.
The difference in electric potential between two points is the electric voltage between these points. We don't have a special name for the gravitational potential difference.