8.02  Physics II

Most of the groups chose the length of the Gaussian surface to be L, which is the same as the charged cylinder's. Since Gaussian surfaces are always chosen arbitrarily, we should use a different variable for its length, say l. Only 3 goups out of 40 noticed this point. Please remember that this arbitrary length l will never appear in the last answer.

It is also important that if you choose the Gaussian surface length to be L, you need to take into account the edge electric field, which is usually difficult to calculate. In this problem, it is assumed that L was large and the edge effect can be neglected.