Question

When a magnetic field is applied on a stationary electron, it

• A. remains stationary
• B. spins about its own axis
• C. moves in the direction of the field
• D. moves perpendicular to the direction of the field
• E. moves opposite to the direction of the field

Hint:

Magnetic fields do not perform work on charges because the force is always perpendicular to velocity. If velocity is zero, there is no force at all.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
A magnetic field exerts a force on a charged particle only when the particle is in motion relative to the magnetic field.
Step 2: Key Formula or Approach:
The Magnetic Lorentz Force is given by: \[ \vec{F} = q(\vec{v} \times \vec{B}) \] In magnitude: $F = q v B \sin\theta$
Step 3: Detailed Explanation:
For a stationary electron, the velocity $v = 0$.
Substituting $v = 0$ into the force equation: \[ F = q(0)B \sin\theta = 0 \] Since there is no magnetic force acting on the stationary electron, there is no change in its state of rest.
Therefore, the electron will remain stationary.
Step 4: Final Answer:
The electron remains stationary.