Question

hey, in the ocw of electricity and magnetism there is question that i didn't understand. http://ocw.mit.edu/courses/physics/8-02sc-physics-ii-electricity-and-magnetism-fall-2010/electric-fields/electric-fields-and-continuous-charge-distributions/MIT8_02SC_challenge_sol04.pdf

in problem 1 did exactly what they answer but the diffrence is the direction of the field of the semi-infinite rod. I did that the direction is rejective and they do that the direction is attractive, how can it be attractive?! electric field indicates the direction if positive charge would be there.

Answer 1

This problem is complicated for electricity and magnetism but you may solve for simple problem with coulombs law and then same idea used here for line of charge distribution for the direction of the force and attraction and repulsion is like positive charge have field line away from the charge or distribution and negative field line towards the charge and that is why same charge repel and opposite charge attract

Answer 2

do you need more explation? @kalonimus

Answer 3

no, thank you, I understand

Answer 4

Also you can go through the physics books by resnik, halliday ,walker and read chapter for electricity and magnetism and hope you will be clear .