Magnetic Field affect on charges

[Chaotic Boredom]

Alright, I know what will happen to an electrical charge in a magnetic field, what I'm a bit fuzzy on is why it happens, I don't recall my teacher going over it at all in class, can anyone clarify why magnetic fields cause perpendicular motion?

 

[Claude Bile]

Magnetic phenomena can be derived from electric phenomena by taking relativistic effects into account.

Consider a current carrying wire, and an electron traveling in the same direction as the current flow. Relativity dictates that, from the electron's frame of reference, the wire is compressed in the direction of travel.

Now, the positive, immobile charges will be compressed slighly more than the negative, mobile charges becuase of the slight difference in their velocities relative to the electron. The electron 'sees' a net positive charge on the wire, because the density of positive charge is slightly greater than the density of negative charge. Thus the electron is attracted toward the wire.

This is the same behaviour that magnetism predicts. Moreover, relativity demands that the force should vary with velocity (since the compression effect will be enhanced), as we would expect from magnetism.

This is by no means a comprehensive analysis, it is intend to provoke a little bit of thought. Griffiths' Intro to Electrodynamics has a nice chapter electromagnetism and relativity.

Claude.

 

[Graeme Robinson]

The motion of charges in a magnetic field is known as the Lorentz force. This force is perpendicular to both the direction of the magnetic field and the direction of the charge's velocity. It is caused by the interaction between the moving charge and the magnetic field.

To understand why this happens, we need to look at the fundamental nature of a magnetic field. A magnetic field is created by moving charges, such as those found in a wire carrying an electric current. When a charge moves through a magnetic field, it experiences a force due to the interaction between its own magnetic field and the external magnetic field.

This force is only present when the charge is in motion. When the charge is at rest, there is no interaction with the magnetic field and therefore no force acting on it. However, when the charge is moving, its magnetic field interacts with the external magnetic field, resulting in a force that causes the charge to move in a direction perpendicular to both the magnetic field and its own velocity.

This perpendicular motion can also be explained using the right-hand rule, where the direction of the force can be determined by the direction of the magnetic field, the direction of the charge's velocity, and the direction of the force using your right hand.

In summary, the perpendicular motion of charges in a magnetic field is due to the interaction between the charge's own magnetic field and the external magnetic field, resulting in the Lorentz force. This force is only present when the charge is in motion and is perpendicular to both the magnetic field and the charge's velocity.