Is Work Done Against Magnetic Force in Griffiths's EM Example?

[neelakash]

After reading the example of a current carrying wire frame "carrying up" a weight in Griffiths's EM book (#ch 5,p-210) a numerous times,...,just now it seems to me that I missed an important point to note earlier.
I am quoting from him."...but now it also has a horizontal component (quB), which opposes the flow of current..."
This means as if unaided charges will slow down.But that is not possible.In fact the battery-aided charges continue to execute w motion along horizontal,allowing the magnetic force component to act on themselves.
See that the magnetic force component quB and the w motion of charges are occurring along the same line.Should not we say that work is being done against magnetic force or, it is doing a negative work?

 

[gtoguy97]

But in actuality,the Lorentz force,quB, is doing a positive work. The answer is that the battery-aided charges are also receiving energy from the same source that is providing the current.This energy is imparted to the charges and so when they execute w motion along horizontal,they have an additional energy and the magnetic force component quB is acting on them which adds to their energy. So the work done by the magnetic force component is actually the conversion of the electric energy of the battery to kinetic energy of the charges.

 

[charng]

Thank you for sharing your thoughts on Griffiths's concepts. It is important to critically analyze and question the material we read in order to fully understand it. After reviewing the example of the current carrying wire frame in Griffiths's book, it seems that you have identified a key point that may have been missed earlier.

You are correct in noting that the horizontal component of the magnetic force (quB) opposes the flow of current. However, this does not mean that the charges will slow down. In fact, as you mentioned, the battery-aided charges will continue to execute a motion along the horizontal direction, allowing the magnetic force component to act on them.

It is important to note that the magnetic force and the motion of charges are occurring along the same line. This means that the work being done by the magnetic force is actually perpendicular to the motion of the charges. Therefore, we cannot say that work is being done against the magnetic force or that it is doing negative work. Instead, we can say that the magnetic force is exerting a force on the charges, causing them to experience a change in direction.

I hope this clarifies your understanding of this concept. It is always important to carefully read and analyze scientific material to fully grasp the concepts being presented. Keep up the critical thinking and questioning in your studies!