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Homework Help: Comparison of Gravitational, Electric, and Magnetic Fields

  1. Dec 22, 2008 #1
    1. The problem statement, all variables and given/known data

    Which two of the three types of fields in the title of this are thread are the most similar? Provide supporting evidence?

    2. Relevant equations

    -Source: point mass
    -Field intensity proportional to: M/r^2
    -Range: long range
    -Strength: weak
    -Direction of field lines: toward center of mass

    Electric Fields:
    -Source: point charge
    -Field intensity proportional to: Q/r^2
    -Range: short range
    -Strength: strong
    -Direction of field lines: toward center of charge

    Magnetic Fields:
    -Source: no point source, dipole required
    -Field intensity proportional to: n/a because no point source
    -Range: short range
    -Strength: strong
    -Direction of field lines: depends on the direction of the motion of a charge generating the magnetic field lines. otherwise they go from north to south.

    3. The attempt at a solution

    I think that gravitational and electric fields have more in common, but I think this is a subjective question. Even so I'm not quite sure so I was wondering if anyone could tell me otherwise. It would be of much help in understanding these three fields.

    Here's my reasoning for gravitation and electric:

    They both have a point source, and with this point source they both have a field intensity that is proportional based on the inverse square law.

    Both exert force from a distance with no contact.

    The field strength of both is also determined by the unit property of the object causing the force (i.e. mass or charge)

    However here are also some major differences:
    -gravitational can only attract while electric can attract and repel
    -you can't shield yourself from gravitational force, but you can from an electric force with insulation, etc.

    Anyways that's my reasoning but I was wondering if electric fields and magnetic fields have more in common in terms of number of similar characteristics. For example they both have a short range yet strong strength of force, and their field diagrams involve curvature (when an electric field involves opposite charges).

    Help please, is there an objective answer?
  2. jcsd
  3. Dec 22, 2008 #2


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    Science Advisor
    Homework Helper

    The main difference between electric and magnetic forces is the absence of magnetic monopoles. But they are still both described by the same equations (Maxwell's) and in relativity they can transform into each other. It's a little subjective, but I'm going to agree with you. Electric and magnetic fields are different aspects of the same force. Gravity (currently) is not.
  4. Dec 23, 2008 #3
    Technically this is incorrect. The field intensity is directly proportional to a few things... I'll try and find an equation, but likely for the scope of your current course it's irrelevant.

    No, not really. It's not true that there's no magnetic monopole, there's just no magnetic point charge. So, as far as how similar the fields are to one another, I would say that gravitational and electric fields are closest --based upon the equations. The inverse square law describes both.
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