# Electric field problem

1. Aug 9, 2006

### ELHEK

Hey ppl! anyone who can help me with this i will be so grateful! ive been stuck on it for 2 days(dumbarse:grumpy: ) thx!

1) A proton orbits a long chared wire, making 1.0x10^6 revolutions per second. The radius of the orbit is 1.0cm. What is the wire's linear charge density?

2) Show that the on axis electic field of a ring of charge has the expected behaviour when z<<R and when z>>R.

The answer to the first questions is -2.29nC/m, but im clueless about how to go about it, i've also tried applying circular kinematics but have not been successful. The second question i am absolutly dumbfounded by. Thx again anyone who helps!

2. Aug 9, 2006

### Päällikkö

1) How can you relate the linear charge density and the electric field generated by the wire? (hint: Gauss)

2) Do you know how to (at least in principle) determine the electric field on the axis? (hint: there's no shortcut here)

3. Aug 9, 2006

### ELHEK

tis alright ive solved em both thx anyway