# Electric field around tape

So, there's a tape with width of 2a, -a on the -y and a on the y, and it very long, penetrating the the plane of picture, it's charge density (dQ/dS) is

σ=σ0 * y /a , σ0 is a constant.

What is the electric field in point A(a.0)?

I tried solving this using charged disk, expressing electric field over polar coordinates etc., that is when there's a uniform charge. But I have no idea how to express y using shapes. What to do? • What is "A(a.0)"? Where is it? Your graph is just an empty graph of x and y - is there any relevance to this empty graph? Oct 23 '14 at 22:54
• A point with those coordinates, it's a half of the width on the x axis. I wanted to help you visualize. You can't see the length of the tape, because it's penetrating the plane of the system, it's very thin so nothing on x, and the only dimensions are from a to -a, on y axis. Oct 24 '14 at 7:02

I think you must use the superposition principle of the field in this case, and consider the problem as a distribution of charge along a line from a to -a, because the contribution to the field of the charge along the z axe is 0, the field in this case is always parallel to the surface xy. The problem is to build the right integral considering a dE and a dL (along the y axe). 