# Concentric cylinders and grounding

1. Oct 7, 2004

### Allday

OK, so we have a coaxial cable that consists of a solid cylinder at the core and two concentric cylindrical shells. All the components are conductors. The outer surface of the outer cylinder is grounded and the inner solid cylinder has a linear charge density of lambda.

Disregarding the gounding for now we know that this inner charge will induce charges on the outer shells. negative lambda on the inner surface of the inner shell, positive lambda on the outer surface of the inner shell, negative lambda on the inner surface of the outer shell, and positive lambda on the outer surface of the outer shell.

The question is will the grounding of the outer surface of the outer shell allow electrons to flow there and cancel the positive lambda on the outer surface of the outer shell? Grounding means the potential is zero, but in this case does it also mean the charge is zero? Any suggestions on how to discuss this process in a lecture would be helpfull.

Thanks

Last edited: Oct 7, 2004
2. Oct 8, 2004

### ehild

The surface charge density at the outer surface of the outer shell becomes zero. So this shell gets a net charge equal in magnitude and of opposite sign to that of the inner core.

ehild