- #1
modulus
- 127
- 3
With my term-end examinations fast-approaching, I sat down to revise my entire senior year physics syllabus. As I was reading through electromagnetic induction, I found myself in the same state of utter confusion that I found myself in when I first studied about Lenz's Law and Eddy Currents. But this time, I think I am in a position to better justify the ideas I am developing.
It seems to me that magnetic fields are just convenient conceptualizations, which allow us to account for a number of energy transfers in an elegant manner. For example, when extended metal (para-magnetic) objects enter a magnetic field, they develop eddy currents, which are oriented so as to oppose the motion otherwise. Another example is the force that pulls a current loop back into the magnetic field as it is being pulled out by an external agent.
In both cases, the work done by the external forces that would otherwise show up as kinetic energy, show up as heat (the eddy currents, the induced current). So, essentially, there is just a transfer of energy (from kinetic to heat). But if we want to explain the slowing down of the metal object or the current loop in terms of forces, then magnetic fields 'allow' us to do that. In this sense, they just seem to be convenient (and astonishingly elegant) mathematical vector fields that just 'work'!
What strengthens my resolve in this matter is Joule heating. We say that when a current flows through a resistor, there is heat energy dissipated apparently, the work done by the battery or cell has been converted to thermal energy). But what about the magnetic field the wire sets up? That is supposed to hold energy within it's 'volume', right? Moreover, it does not change with time. Somehow, the heat energy has been converted into a magnetic field, which persists (this is in contrast to what happens in eddy currents, where the result is a 'dispersion' of energy from kinetic to thermal energy, which, as it seems, is entropically favorable).
If I am going on the wrong track here, If there is a serious flaw in my reasoning, someone throw me back on the right track. Because if this is right, then the implications of it are pretty interesting...
It seems to me that magnetic fields are just convenient conceptualizations, which allow us to account for a number of energy transfers in an elegant manner. For example, when extended metal (para-magnetic) objects enter a magnetic field, they develop eddy currents, which are oriented so as to oppose the motion otherwise. Another example is the force that pulls a current loop back into the magnetic field as it is being pulled out by an external agent.
In both cases, the work done by the external forces that would otherwise show up as kinetic energy, show up as heat (the eddy currents, the induced current). So, essentially, there is just a transfer of energy (from kinetic to heat). But if we want to explain the slowing down of the metal object or the current loop in terms of forces, then magnetic fields 'allow' us to do that. In this sense, they just seem to be convenient (and astonishingly elegant) mathematical vector fields that just 'work'!
What strengthens my resolve in this matter is Joule heating. We say that when a current flows through a resistor, there is heat energy dissipated apparently, the work done by the battery or cell has been converted to thermal energy). But what about the magnetic field the wire sets up? That is supposed to hold energy within it's 'volume', right? Moreover, it does not change with time. Somehow, the heat energy has been converted into a magnetic field, which persists (this is in contrast to what happens in eddy currents, where the result is a 'dispersion' of energy from kinetic to thermal energy, which, as it seems, is entropically favorable).
If I am going on the wrong track here, If there is a serious flaw in my reasoning, someone throw me back on the right track. Because if this is right, then the implications of it are pretty interesting...