Beam of Electrons?

Question

A magnetic field can deflect a beam of electrons but is unable to speed them up. Why is that?

Answer 1

Because the force is perpendicular to the velocity. To speed something up, you have to push in the same direction as the velocity.

Answer 2

The Conservation of Energy requires that...



accelerating or orbiting electrons do not dissipate energy by radiation.



If the electron is moving in the magnetic field it will “see” an electric field. This is induced by the relative motion of the magnetic field creating an electric field from E = ( v x B ), where v is the relative vector velocity of the magnetic field with respect to the electron, and B is the vector magnetic field strength, and E is the perceived vector electric field.



The induced electric field is always normal to the velocity vector, so the electron sees a transverse field that forces it sideways; this force is termed the “Lorentz Force”. Because it is normal to the velocity vector at all times it will turn the straight-line path of the electron into a curved one.



Dr. H

Answer 3

An electron is a magnetic dipole (magnetic monopoles do not exist.) Therefore, it does not have a net "magnetic charge" so to speak. A dipole cannot be accelerated by a magnetic field. It can be caused to precess by a longitudinal magnetic field or to deflect by a transverse magnetic field.