# Radius of motion of particle through magnetic field.

A singly charged particle of Li-7, an isotope of Lithium, is accelerated through a potential difference of 229V and then enters a magnetic with magnitude 0.723T perpendicular to the path of motion. What is the radius of the ion's path in the magnetic field?

I know that $$$R = \frac{{mv}}{{\left| q \right|B}}$$$, but I am unsure how to calculate the velocity, and I certainly don't know how to calculate the charge. My educated guess is that velocity and charge are directly proportional over a potential difference so that they don't matter in this problem, but I don't have any equations relating the three.

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'Singly charged' means having the charge of one electron. So you do know the charge and now can calculate the velocity generated by the voltage drop.

Astronuc
Staff Emeritus