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Discussion in 'Area 51' started by Garrybg, Dec 11, 2019.
How are conduction and induction alike and how are they different?
In what context? Electrical current?
Context in the field of physics and thermodynamics.
Physics AND thermodynamics?
Welcome to the forum Gary. Despite the name, remarkably little of the conversation that happens here is about rocket science.
I am going to guess that you are asking about induction cooktops or induction furnaces?
In which case, really short answer: You can induce electrical currents in something that is electrically conductive by putting it in a time-varying magnetic field. Those electrical currents will generate heat in the material through which they flow by a process called ohmic heating (or joule heating).
In a conduction cooktop the current is applied directly to a conductor (the heating element) to heat it up, and heat is transferred to the cookware by thermal conduction.
Conduction is direct energy transfer through physical contact of matter.
Induction is indirect energy transfer from one media to another without physical contact.
Except when it is radiative transfer.
Radiative transfer is a form of induction.
Convection is a form of conduction.
I disagree on the former. So there.
Plus which, in thermal conduction, momentum is transferred between particles by the electromagnetic interaction; so, conduction = radiative transfer = induction.
Therefore the OPs question is meaningless. Induction and conduction are the same thing, which is how solar cells work... oh, wait.
Just don't mix the matter with the antimatter!
Induction does not require physical proximity. An electric, magnetic, or electromagnetic field transfers energy without a transfer medium containing matter. Radiative heat is induction by electromagnetic waves typically in the infrared range. A microwave oven is induction using electromagnetic waves around 2.4 GHz. A transformer or motor works by magnetic field induction.
Conduction requires physical contact between matter at the molecular level. The kinetic energy in an atom is not the same as Newtonian kinetic energy of bulk matter. Thermal conduction requires boltzman distribution (quantum thermal-kinetic probabilistic motion) energy transfer. Electric conduction requires transfer of free electrons between atoms (or tunneling).
Summary: induction is a macro-level field phenomenon which works by field effects without a medium (works in a vacuum); conduction is quantum-level phenomenon which requires physical proximity of matter.
Does energy transfer need to happen for induction? For example I can induce a force with magnetic field on a current carrying conductor with no work being done.
Yes. Those are all words.
We are all going to feel pretty silly when the OP comes back and explains that he meant to ask about the difference between induction and deduction, or that he was talking about hypnotic induction, or about the Sigma Pi Sigma lavaliere ceremony (Oh, how proud I was at my induction into the society)...
The answer I'm most interested in is why the OP chose to make this their first post to TRF... and in Area 51 no less.
I like the cut of his jib.
Well where else was he supposed to get a straight answer?
It was not well explained by the orange-apron employee in the Home Depot appliance department. That guy was on his way back from the bathroom to the paint department and was trying to be helpful, but he made a terrible hash of it -- mixing up Wiedemann-Franz free-electron theory with the Drude model -- when somebody else walked up and asked him if he could copy a house key.
Holy crap, how much do I NOT want to get back to this pile of exams.
edit: my spellchecker knows that "wiedmann" is misspelled, but still redlines my last name.
Spellchecker knows its beer.
Yes, written correctly for readers unlike you.
Energy was required to induce the magnetic field. Energy is stored in the field even though no work was done (ideal circuit). The energy may be transferred and stored elsewhere (capacitor as a static electric field for example) or the energy can be dissipated as heat, or the energy could do work by moving a solenoid or rotate a motor.
So in the case of a no work motor (stall) or solenoid we are inducing potential energy, correct?
Wouldn't it be even funnier if somebody on this thread was an in-real-life solid state physicist?
While trying to work our whether you are saying that you are posting for people who aren't like me, or that -- unlike me -- you are posting for people, it occurred to me that whatever app you are using to access the forum might be hiding URLs from you.
Thank you, Guys!
This is the strangest damn rickroll.
My answer is more complete, beyond his electrical and magnetic examples.
Also, his answer is not correct saying "Induction: Can only be applied with A.C.". Alternating current is a steady-state sinusoidal excitation. Induction will happen with any current that changes with time: any transient current change, single event or periodic.
There are two possibilities here:
1) The OP thinks that his question -- which is suspiciously similar to the title of the handwaving non-explanation to which he links -- is a meaningful combination of words (it is not)
2) The OP is messing with us.
If it is the former -- that the OP really thinks that "compare and contrast induction and conduction" is a thing, then there isn't much that we can do to clear up his confusions in this format. Describing the relationship between the conduction current and the displacement current comes at the end of a longish course of instruction in electrodynamics -- and there is no meaningful way to state that relationship without recourse to integral equations or differential equations or phasors or -- cough -- tensors.
If it is the latter, then it is safest to enable secure browsing before clicking on any links he posts.
I've taken grad level courses in emag/electrodynamics. I've taught grad level complex variables. There's no need to learn any of that to allow the average person to have a general understanding of the concepts. No one is asking to solve for divergence and curl of the E & B field vectors in 3D space for an arbitrary excitation with relativistic affects. Except you, maybe. ;-)
There's no way to know why the question was asked here. But, the question is legitimate ("a thing"). The general answer is pretty clear as I've summarized here. If someone wants to know more, start with https://www.feynmanlectures.caltech.edu/ . Others may find it easier to drink a beer and ignore this topic. QED.
It is an imperfect analogy, but the flavor of the OP's question is a little like "How are postage stamps and postal workers alike and how are they different?"
The relationship between the two items is much more than a summary of similarities and differences, and any complete accounting of that relationship will depend upon a nuanced understanding of more things than how mail gets moved around.
Not to put too fine a point upon it, but a general answer is nonsense. You can spray a lot of words around the topic and (maybe) generate the sensation of having explained something and (maybe) the sensation of understanding in your audience -- but really, we are talking about physical laws. The words just fill up the pauses you must take while struggling through the math.
And it is a terribly disingenuous to glibly drop phrases like "sinusoidal excitation" and fluent nonsense like "Thermal conduction requires boltzman distribution (quantum thermal-kinetic probabilistic motion) energy transfer" and then claim to be writing for a layperson who need not concern himself with mathematical complexities.
Anyway, I'll see your Feynman lectures (about which, please) and raise you two Richard-actual-Feymans and an Eugene Wigner (with subsequent commentaries). I'll take my answer off the air.
What? No Wikipedia link this time?
In the real world where real people make real things and want to understand what they see and use, it is a legitimate question and there's no purpose in looking down your nose at my real-world explanation.
And you missed the irony of my "big words" as fodder for you and only you. ;-)
No need to continue this thread.
Separate names with a comma.