Question

At one instant an electron is moving in the positive x direction along the x axis in a region

where there is a uniform magnetic field in the positive z direction. When viewed from a point
on the positive z axis, it subsequent motion is:

A) straight ahead
B) counterclockwise around a circle in the xy plane
C) clockwise around a circle in the xy plane
D) in the positive z direction
E) in the negative z direction

Answer 1

The electron moving in a uniform magnetic field in the positive z-direction will experience a force causing it to move in counterclockwise circles in the xy plane when viewed from the positive z axis.

Step-by-step explanation:

When an electron is moving in the positive x-direction and there is a uniform magnetic field in the positive z-direction, this scenario is described by the right-hand rule for negative charges, which predicts the force direction for a moving charged particle in a magnetic field. However, since electrons are negatively charged, the force direction is opposite to the prediction of the standard right-hand rule. When viewed from above (along the positive z-axis), if an electron is moving in a field directed outwards towards you, it will experience a force that causes it to move in counterclockwise circles in the xy plane. Therefore, the correct answer to the question is B) counterclockwise around a circle in the xy plane.