## help

tizihuxi
Posts: 6
Joined: Tue Jun 05, 2018 9:50 pm

### help

A beam contains 2.0x10 8 doubly charged positive ions per cubic centimeter, all of which are moving north with a speed of 1.0x10 5 m/s. What is the magnitude of the current density.

I know what formula to use, but I don't know what to do because I don't know what it means when the question states double charged.

jeff
Posts: 39
Joined: Mon Mar 05, 2018 11:54 pm

### Re: help

Hi tizihuxi,
tizihuxi wrote:
Thu Jul 12, 2018 4:15 am
A beam contains 2.0x10 8 doubly charged positive ions per cubic centimeter, all of which are moving north with a speed of 1.0x10 5 m/s. What is the magnitude of the current density.

I know what formula to use, but I don't know what to do because I don't know what it means when the question states double charged.
When it says "doubly charged," that means that these particles have a charge that is twice that of the proton. (We would say that a proton is singly charged.)

Since a proton has a charge of 1.6 x 10^-19 C, you would double that value to get the charge of the particles in the problem.

I hope this helps. Let me know if you still have any questions.

tizihuxi
Posts: 6
Joined: Tue Jun 05, 2018 9:50 pm

### Re: help

I got the answer. thank you