Question

Observing the electron beam from the front of the apparatus, which way does it curve under the influence of the magnetic field (clockwise or counterclockwise)? Based on this, in which direction must the magnetic field produced by the coils be pointing? Justify your answer.

(We used a Helmholtz coil e/m apparatus to measure the charge to mass ratio for an election by producing a magnetic field perpendicular to the direction of the travel of the electrons)

Answer 1

lets consider some points,

- current flow direction is opposite to the direction of electron flow

- flemings left hand rule tells about the force experienced by a current carrying system in a magnetic field

Now, if magnetic field is into the coils and current flows from left to right the deflection will be in clokwise direction

if the magnetic field is revered the deflection wll be anticlowwise.

the force experienced by the electrons can be quantitatively given by lorentz forces

F = qE + qv × B where q is the charge, v is the velocity , E is the electric field , B is the magnetic field

and qvXB is the cross product,