Consider different infinitely long straight cylinders, each having distinct charge distributions. Among these, only the systems with a charge density that does not vary when you rotate it and does not vary along the axis length possess cylindrical symmetry. In comparison, the others do not have cylindrical symmetry. When there is a cylindrically symmetric charge distribution, a cylindrical Gaussian surface is constructed to obtain the electric flux. The electric field through the curved part of this surface is parallel to the area vector and has the same magnitude over the circumference and length. From this, the flux over the curved portion is obtained. The electric field through the flat ends is perpendicular to the area vector, making the flux zero. By combining both, the total flux through the Gaussian surface is obtained. Since the charge density is constant over the Gaussian cylinder length, the charge enclosed is the product of line charge density and cylinder length. According to Gauss' law, the electric field magnitude is obtained, which varies inversely with distance from the line charge.