Monday, February 1, 2010

Irodov Problem 3.13

a)


















Consider an infinitesimally small section of the rod of length dx that is at a distance x from the center of the rod. The charge contained in this infintesimally small section of the rod will be




The distance of this infinitesimally small section from point O is given by . The electric field generated by this infinitesimally small section of the rod is thus given by,





From elemetary geometry we know that,








From (1),(2), (3a) and (3b) we have,













b)












Consider an infinitesimally small section of the rod of length dx that is at a distance x from the center of the rod. The charge contained in this infinitesimally small section of the rod is given by (1). The distance of this section from O is given by r-x. Hence, we have,

2 comments:

  1. Sir please explain why is it that when I used Gauss' Law to find the field in the first case, (by constructing a Gaussian cylinder around the rod), I got the wrong answer.

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    Replies
    1. There are constraints for APPLYING Gauss Law
      Electric field should be constant and perpendicular to area

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