Question

An infinite cylindrical shell of radius a has a uniform surface charge density (sigma). What is the electric field at a pont a distance r>a away from the axis of cylinder?

Answer 1

Apply Gauss law to another cylindrical shell of radius r.

Answer 2

what length should i used?

Answer 3

Any arbitrary length h. It will disappear from the expression at the end.

Answer 4

Spherical guassian surface is more preferred.