The correct relation for the charge-to-mass ratio (e/m) of an electron is?

e/m = 2E/B²r

e/m = v²/B²r²

e/m = v/B²r

None of these

Explanation

e/m = 2E/B²r²

The formula is derived by equating the magnetic Lorentz force to the centripetal force and using the kinetic energy gained from the accelerating voltage E.

This formula correctly relates the charge-to-mass ratio of an electron to the magnetic field B, radius of the circular path r, and accelerating voltage E.