A beam of electrons is undeflected when it passes simultaneously through an electric field of 10 N/C perpendicular to its path and a magnetic field of 2 *10^-4 T perpendicular both to its path and to the electric field. The speed of the electrons is approximately A) 2 * 10^-4 m/s B) 1 * 10⁴ m/s C) 5 * 10^-4 m/s D) 2* 10⁴ m/s E) 5*10⁴ m/s

Question

Quizplus · Accepted Answer

The speed of the electrons is given by the condition that the electric force equals the magnetic force: $ E = vB $. Solving for $ v $, we have $ v = \frac{E}{B} = \frac{10}{2 \times 10^{-4}} = 5 \times 10^4 $ m/s.

A Beam of Electrons Is Undeflected When It Passes Simultaneously