I calculating the number of Electrons? (Current/Electron Density/Velocity)

[bmb2009]

Homework Statement

How many protons are in the beam traveling at the speed of light in the Tevatron at Fermilab, which is carrying 11.17 mA of current around the 6.3-km circumference of the main Tevatron ring?

Homework Equations

Not sure...

The Attempt at a Solution

I don't know how to calculate the the protons (electrons). I tried multiple different things but al the equations I have use the Cross Sectional area value (A) which can't be found from the given information.

I tried manipulating such equations as

current density = (number of electrons)(e)(drift velocity)

and other similar equations but the all contain some form of the value of A?

Please help :(

 

[voko]

What is current?

 

[Liquidxlax]

What is current?

and how do you find J {current density} from I {current} and a circumference?

 

[voko]

and how do you find J {current density} from I {current} and a circumference?

What is the significance of current density here?

 

[bmb2009]

Ok got it! Thank You!