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Finally, for your question above, you really need to give more information about it so people can understand what you are asking about.
(ah, I write too much... someone else slipped in before I finished! )
A line charge of 45 nC is uniformly distributed along positive Z axis.Two point charge of 75 nC are located at (3,0,0) and (0,3,0). Determine the potential difference PQ if P is at
(3,4,0) and Q is at (5,4,3).
Please re-post there. First, read the "Guidelines for Students and Helpers" which are posted near the top of that forum. Then, start a new thread, fill out the template that you will see, and show what work and thoughts you have tried already.