Gravitational Field, Electric Field and Magnetic Field
Comparative study between the Gravitational Field, Electric Field and Magnetic Field
GRAVITATIONAL FIELD 
ELECTRIC FIELD 
MAGNETIC FIELD 

Source 
Body mass (punctual or mass distribution) 
Electric charge (punctual or mass distribution) Magnetic field variable in time 
Electric charge in motion – Electric current Electric field variable in time

Force 
Proportional to the mass on which it acts
Attraction
Open and Incoming 
Proportional to the electrical charge on which it acts
Attraction or Repulsion
Open Incoming: q Outgoing: +q

Proportional to the electrical charge on which it acts
Attraction or Repulsion
Close (from N to S) Solenoidal field 
Features 



Conservative Field
In a Conservative Field (Gravitational Field and Electric Field) the equipotential surface is the one which is integrated by all the points where the potential has a same determined value, existing different equipotential surfaces according to the value of the potential.
As it is deduced from Coulomb’s Law, the potential due to a punctual charge is given by the following formula:
From this formula it is deduced that the equipotential surfaces of the Electric Field created by a punctual charge are concentric spheres with the charge, since all their points are at the same distance, the radius of the charge, and therefore, the same potential:
As seen in the drawing, the lines of force and the equipotential surfaces are perpendicular to each other. This shows that no work is done when moving a charge within the same equipotential surface:
And also:
In each of its points the line of force is tangent to the vector Field Intensity E, and, consequently, also to force F
Non Conservative Field
In a NonConservative Field (Magnetic Field) there is no energy associated with the fixed points of the field, as the force of Field of Intensity of Velocity depends with the electric charge q that moves in its sine
This prevents that a potential function is defined that only depends on the position of the bodies in the Magnetic Field, that is, there is no associated potential energy that is retained when a particle moves within the field.
You can download the App BioProfe READER to practice this theory with selfcorrected exercises.