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

Bioprofe | Exercises of Physics, Chemistry and Mathematics | Gravitational Field

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Open and Incoming

Proportional to the electrical charge on which it acts

Attraction or Repulsion

Bioprofe | Exercises of Physics, Chemistry and Mathematics | Electric Field

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Open

Incoming: -q

Outgoing: +q

Proportional to the electrical charge on which it acts

Attraction or Repulsion

Bioprofe | Exercises of Physics, Chemistry and Mathematics | Magnetic Field

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Close (from N to S)

Solenoidal field

Features

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Conservative
It is a central field
The work required to move a mass between two points of the field does NOT depend on the trajectory

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Conservative
It is a central field
The work required to move a mass between two points of the field does NOT depend on the trajectory

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Non Conservative
It depends on the speed
The work required to move a mass between two points of the field DOES depend on the trajectory

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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:

Bioprofe | Exercises of Physics, Chemistry and Mathematics | Gravitational Field, Electric Field and Magnetic Field

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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:

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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:

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And also:

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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 Non-Conservative 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

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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.