wolfblum
- 5
- 0
Hello Zooby,
I don't know how to do those nice quote panes yet, so please bear with me.
"Acyclic EM interactions"? A new term to me. What's the specific definition?
Acyclic Electromagnetic interactions are those that are time invariant (as in any true homopolar machine.) This, as opposed to the Cyclical (time varying) EM interactions found in all other electromagnetic machinery (AC or DC.)
As an example, a copper disk rotating perpendicular to an applied uniform and symmetrical magnetic flux field will never experience any flux density variations (or polarity variations.) Cylindrical topologies are also possible, as you already know.
As a result, the conduction electrons in the disk (i.e., the so-called free electron gas) experience the Lorentz force and a displacement current flows, leading to the EMF gradient observed between the center and periphery of the disk.
Please do not amalgamate anything, mercury is nasty stuff! Faraday used to lick his experimental apparatus to have his tongue "sense" electric potential, that's what probably caused his mental and health problems in later life and his death. FYI, I have a complete original set of Faraday's diaries and can tell you that he did co-rotate a disk with a cylindrical magnet and observed the generation of EMF (although he was never certain himself about the rotation of the field itself.)
Further stuff, the term unipolar should not be used, it means "having one pole" and that is not possible. The term homopolar is acceptable and means "poles on the same center." One has to be carefull though, for example, most of Faraday's reported disk experiments may well be classified as homopolar, in that the magnetic poles were on the same center, however, they were not acyclic, in that the rotating disk axis was not on the magnetic pole axis. So the EMF that Faraday measured was really due to eddy currents (if he had been able to measure drag torque as he turned the disk faster and faster, even with no brush connections and external circuit, he would have noticed the required effort increase and that the temperature of the disk was also rising. Hmm... just the exact same setup as the brake disk in our electric watthour meter on the side of the house!)
I'll comment more on the "spin" aspects involved in magnetic fields later.
Ciao - Wolf
I don't know how to do those nice quote panes yet, so please bear with me.
"Acyclic EM interactions"? A new term to me. What's the specific definition?
Acyclic Electromagnetic interactions are those that are time invariant (as in any true homopolar machine.) This, as opposed to the Cyclical (time varying) EM interactions found in all other electromagnetic machinery (AC or DC.)
As an example, a copper disk rotating perpendicular to an applied uniform and symmetrical magnetic flux field will never experience any flux density variations (or polarity variations.) Cylindrical topologies are also possible, as you already know.
As a result, the conduction electrons in the disk (i.e., the so-called free electron gas) experience the Lorentz force and a displacement current flows, leading to the EMF gradient observed between the center and periphery of the disk.
Please do not amalgamate anything, mercury is nasty stuff! Faraday used to lick his experimental apparatus to have his tongue "sense" electric potential, that's what probably caused his mental and health problems in later life and his death. FYI, I have a complete original set of Faraday's diaries and can tell you that he did co-rotate a disk with a cylindrical magnet and observed the generation of EMF (although he was never certain himself about the rotation of the field itself.)
Further stuff, the term unipolar should not be used, it means "having one pole" and that is not possible. The term homopolar is acceptable and means "poles on the same center." One has to be carefull though, for example, most of Faraday's reported disk experiments may well be classified as homopolar, in that the magnetic poles were on the same center, however, they were not acyclic, in that the rotating disk axis was not on the magnetic pole axis. So the EMF that Faraday measured was really due to eddy currents (if he had been able to measure drag torque as he turned the disk faster and faster, even with no brush connections and external circuit, he would have noticed the required effort increase and that the temperature of the disk was also rising. Hmm... just the exact same setup as the brake disk in our electric watthour meter on the side of the house!)
I'll comment more on the "spin" aspects involved in magnetic fields later.
Ciao - Wolf