1. The problem statement, all variables and given/known data A beam contains 4.0x10^8 doubly charged positive ions per cubic centimeter, all of which are moving north with a speed of 1.2x10^5 m/s. (a) What is the magnitude of the current density ? (b) What is its direction? (c) What additional quantity or quantities are needed to calculate the total current in this ion beam? 2. Relevant equations J=I/A=nqv (v = drift velocity) 3. The attempt at a solution Well I tried this (4.0e8)(2)(1.6e-19)(1.2e5) which I thought would give what I wanted but apparently not. I was thinking by looking a dimensional analysis that it has something to do with the seconds in the velocity but im not sure?