A line charge of liner charge density lambda=4.5 nC/m lies on the x axis and extends from x=-5cm to x=5cm. Derive an expression for E_y. I have started with this question and it seems that I have to sum the electric fields in the y direction caused by each dx along the line with a charge dq. I think I understand how to do the integral but I just don't know what the field in the y direction is? Thanks for any help.