A strong magnetic field is applied on a stationary electron. Then the electron.

Question

Accepted Answer

The correct option is (1):
To understand the behavior of a charged particle in a magnetic field, we refer to the Lorentz force equation. The magnetic force ($F\_B$) experienced by a charged particle is given by the formula $\vec{F\_B} = q(\vec{v} 	imes \vec{B})$, where $q$ is the charge of the particle, $\vec{v}$ is its velocity, and $\vec{B}$ is the magnetic field. This equation tells us that a magnetic force acts on a charged particle only if it is in motion and its velocity vector has a component perpendicular to the magnetic field.

In this question, a strong magnetic field is applied to a *stationary* electron. A stationary electron implies that its velocity ($\vec{v}$) is zero. Substituting $\vec{v} = 0$ into the Lorentz force equation, we get $\vec{F\_B} = q(\vec{0} 	imes \vec{B}) = \vec{0}$. This means that the magnetic force acting on the electron is zero. Since there is no force acting on the electron, it will not accelerate or change its state of motion. Therefore, the electron will remain stationary. This fundamental principle highlights that magnetic fields do not exert forces on charges at rest.

The incorrect option is (2) Moves in direction of the field: A magnetic field does not exert a force on a stationary charged particle, so it cannot cause the electron to move. Even if the electron were moving, the magnetic force is perpendicular to the velocity and the magnetic field, not parallel to the field.

The incorrect option is (3) Moves opposite to the direction of field: Similar to option 2, a magnetic field does not exert a force on a stationary electron. If there were a force, its direction would be determined by the cross product of velocity and magnetic field, not simply opposite to the field.

The incorrect option is (4) Moves perpendicular to the direction of field: While magnetic forces are indeed perpendicular to the magnetic field for a moving charge, in this scenario, the electron is stationary. With zero velocity, the magnetic force is zero, and thus no motion, perpendicular or otherwise, will occur.