Question

Study the following three diagrams in which the entry of an electron in a magnetic field is shown. Identify the case in which the magnetic force experienced by the electron is (i) maximum, and (ii) minimum. Give reason for your answers in each case.

Answer 1

Finding the direction of force acting on a current-carrying conductor in a magnetic field is done with the Fleming left-hand rule.

1. The magnetic field line strength can be changed by varying the solenoid’s current, which is adjusted for bar magnets.
   F = qVB sin θ
   ∵ θ = 90°, sin 90° = 1
   F = qVB sin 0°
   F = 0 (maximum)
2. Since the electron's speed in case (C) is parallel to the magnetic field’s direction (B), the force acting on the electron is at its lowest (zero).
   ∵ q = 0°
   F = qVB sin 0°
   F = 0 (minimum or zerro)