# Geiger Counter and Potential Difference

In this problem I am getting stuck on how to find the potential difference. I don't know where to begin. In a Geiger Counter suppose the radius of the central wire is 145 micrometers and the radius of a hollow cylinder is 1.80 cm. What potential difference between the wire and the cylinder produces an electric field of 2.00*10^4 V/m at a distance of 1.20 cm from the axis of the wire?
:grumpy: