Question

A charged particle that is moving in a static uniform magnetic fieldA) may experience a magnetic foce, but its speed will not changeB) may experience a magnetic foce, but its direction of motion will not changeC) may experience a magnetic force which will cause its speed to changeD) will always experience a magnetic force, regardless of its direction of motionE) none of the above statements are true

Answer 1

Answer:

A) may experience a magnetic foce, but its speed will not change

Explanation:

A charged particle moving in an uniform magnetic field experiences a force given by:

$F=qvB sin \theta$

where

q is the charge of the particle

v is the velocity of the particle

B is the magnitude of the magnetic field

$\theta$ is the angle between the direction of v and B

From the formula we notice that:

- if the particle is moving parallel to the field, $\theta=0$, so force experienced by the particle is zero --> so we can exclude option D)

Moreover, the magnetic force experienced by the particle is perpendicular to the direction of motion. This means that:

- The direction of motion of the particle will change --> so we can exclude option B)

In addition, we can notice that since the magnetic force is perpendicular to the direction of motion of the particle, the work done by the force on the particle is zero: this means that the kinetic energy of the particle does not change, so the speed of the particle does not change. So we can exclude also option C, therefore the only correct option is

A) may experience a magnetic foce, but its speed will not change