Acylindrical beam of particles each with charge q and mass m has a uniform initial (charge) density p and radius r. each particle in the beam is initially traveling with velocity v parallel to the beam's axis. consider the stability of this beam by examining the forces on a particle traveling in the beam at a distance r < r from the axis (the center of the cylinder). find the approximate force on a particle at radius r caused by the other particles in the beam. you will need to use gauss's law to calculate the electric field at radius r. describe your work, and do not skip steps; show that you understand gauss's law.

Cells in the nervous system have a potential difference of 70 mv across the cell membrane separating the interior of the cell from the extracellular fluid. this potential difference is maintained by ion pumps that move charged ions across the membrane. is this an emf? select the correct answer and explanation. 1)no. the ion pumps cannot separate charges; thus, they cannot create a potential difference. 2)yes. the ion pumps cannot separate charges, but they still can create a potential difference. 3)yes. the ion pumps can actively separate charge; thus, they can create a potential difference. 4)no. the ion pumps can separate charges, but they cannot create a potential difference.