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Homework Help: What is a field?

  1. Oct 3, 2011 #1
    1. The problem statement, all variables and given/known data
    Could you confirm or refute these ideas?
    1) All fields start from a point charge.
    2) We tend to measure the sum of fields from groups of point charges.
    3) The inverse square portion of the field strength of a point charge is based on the geometry of the surface area of a sphere.
    4) Ignoring any interferences from the environment, the sum of the strength of a field at a distance of a point charge is equal to the strength of the point charge.

    a) Does a field strength at a distance from a point charge exist because of a force or effect that is *moving* through space from the point through a distance? If so, what is the speed of a field ?


    b) Does a field strength at a distance from a point charge exist because of an interaction with a medium in it's direct vicinity which then interacts with a medium in it's vicinity and so on? If so, what would the medium of vacuum consist of? How is it recognized?

    2. Relevant equations
    All inverse square field equations.
    Last edited: Oct 3, 2011
  2. jcsd
  3. Oct 3, 2011 #2
    The reduction in strength is just a result of the fact that you are spreading the field lines more thinly. If you put a dot on a piece of paper and draw lines 15cm long coming from the dot evenly in all directions, you will see that the lines diverge. All a 'field strength' is, is the density of these lines.

    The same occurs for the brightness of the sun (or anything else). The brightness (/field strength) is not dependent on time, but reduces with distance.
  4. Oct 3, 2011 #3
    Last edited: Oct 3, 2011
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