Question

The electron in a hydrogen atom can be thought of as orbiting around the nucleus (a single proton) in a circular orbit of radius 5.28×10−11m  with a velocity of constant magnitude 2.190×106m/s . At t=  0s  a hydrogen atom is placed in a vacuum chamber that is filled with a uniform magnetic field of magnitude 3.3×1011T  pointing in the positive z -direction. The hydrogen atom is oriented such that its electron is orbiting counter-clockwise in the xy -plane at t=  0s .

What is the direction of the magnetic moment of the hydrogen atom at t=  0s ?

In the positive x -direction.

In the negative x -direction.

In the positive y -direction.

In the negative y -direction.

In the positive z -direction.

In the negative z -direction.

The hydrogen atom has no magnetic moment.

Answer 1

The magnetic dipole moment is defined to be a vector pointing out of the plane of the current loop and with a magnitude equal to the product of the current and loop area: The area vector, and thus the direction of the magnetic dipole moment, is given by a right-hand rule using the direction of the currents. The electron by its counter-clockwise motion produces conventional current in the clockwise direction. Hence by using right-hand rule, one can find that at t = 0 direction of the magnetic moment of the hydrogen atom will be in the negative z-direction.