Question

1. A speed selector is a device that uses both electric and magnetic fields to select particles with only a certain value of velocity.

(a) If a positively charged particle goes through a region of space where the electric field points directly upwards and the magnetic field points out of the page, draw a free body diagram indicating the electric and magnetic forces this particle feels.

(b) If the particle can go through this region without being deflected (that is, its velocity stays the same), what does this imply about the magnetic and electric forces? Write an equation that matches your answer.

(c) If the magnitude of the magnetic field is 0.22 T and the particles being selected are those with a speed of 256 m/s, find the magnitude of the electric field.

Answer 1

b) velocity is same. net force is zero

electric force = magnetic force

E * q = q v B

C) B = 0.22 T

speed = V = 256 m/sec

electric field = E = V * B = 256 * 0.22 = 56.32 N/C