- #1

Istiak

- 158

- 12

- Homework Statement
- A cylinder of length l, has a magnetic field B inside it, which is perpendicular to the cylinder axis. An electron of charge -e and mass m enters the cylinder with velocity v along the cylinder axis. If the radius of the cylinder is r=mveB, which of the following ensures that the electron leaves the cylinder with velocity along the cylinder axis?

- Relevant Equations
- ##\vec F=q\vec v\times \vec B##

##\vec F=m\vec g##?

##\vec B=\frac{\mu_0 nI}{4\pi r}##

Since the question says that "velocity along the cylinder axis" and "magnetic field perpendicular to the cylinder axis". So cross product of velocity and magnetic field becomes their magnitude.

##\vec v\times \vec B=||v|| \\ ||B||##

So

##\vec F=qvB##

##mg=qv\frac{\mu_0 nI}{4\pi r}##

At first sight my assumption was electron can leave along the cylinder axis. But when I came up with the equation, I just realized I can't find a relation of between those given options and my results so perhaps electron can't leave along cylinder axis. While posting the question I was thinking that given ##n## in option isn't related to mine. So my attempt is completely wrong.