MH's ideal coil and voltage question

[MileHigh]

Well not from you anyway.

Im fine with the question MH,but it seems you have a little trouble with it.
Im sure all the info you need to catch up,is out there for you to find.

Brad

More making a complete fool of yourself, a spectacle of yourself, by "pretending."

[picowatt]

MH,

Tinman defined CEMF as follows:

When a voltage is placed across a coil, the current will change quickly from zero. This  change creates an expanding magnetic field around the coil, and when this happens,it induces a voltage back into the coil. This self induced voltage is known  as back EMF,or CEMF,and creates a current flow in the OPPOSITE direction to the current flow that induced it in the first place.

Were I grading papers, I would merely have scratched out the words I highlighted in bold above, and replaced "the OPPOSITE direction" with the word "opposition" so that it reads "creates a current flow in _opposition_ to the current flow", just to clarify and be a bit more precise.

If I wanted to nitpick at it a bit further, I might also have circled "CEMF" and wrote "preferred" next to it, and possibly replaced the word "coil" where used with the word "conductor" (unless the question specifically asked about a coil, and not just a generic inductor).

I would also have been tempted to insert "flowing through it" in the first sentence so that it reads "the current _flowing through it_ will change from zero".

However, I would have given full credit for his response, as it demonstrates a basic grasp of the concept.

I know the two of you have been at odds for some time, but the rather demeaning nature of your response seems a bit much. 

PW

[tinman]

No it doesn't create a current flow in the OPPOSITE direction.  That is a nonsensical idiotic fantasy that does not happen and you will never find a single stitch of evidence for that.  It's a bad-old-days belligerent Brad fantasy.



MileHigh

Quote Poynt post 1310
The point being, the cemf, no matter it's value, will effectively be shorted by the load. But as I explained there is no real consequence, because the resulting induced current does the job of limiting the current.

PW post 1333
By definition, the CEMF will oppose _current_ and in order to see the effects of CEMF (as defined), one must measure current.

PW post 1284
As well, it would seem that any device capable of producing a CEMF exactly equal to an applied EMF would prevent current flow.

Citfta post 1301
The CEMF is generated by the increasing magnetic field of the coil as the current rises.  If your claim that the CEMF equals the EMF were true then no current would flow and that means the could NOT BE any CEMF.  Sorry, but your argument makes no sense at all.  I haven't read all the posts in this thread but it appears you are the only one that believes CEMF can equal EMF.

Poynt post 1218
The higher the inductance, the higher the induced cemf for a given frequency. At some point (either relatively large L or high frequencies) the cemf will equal the applied voltage (or it may be more correct to say the induced current will equal the applied current) and the net resulting current will be minimal.

Post 1208-your reply to me on a question i asked point
And you are still stuck.  Surprise surprise.  The CEMF is identical to the applied EMF.  This was also covered in the thread multiple times.
Thankfully the rest of us here put an end to that rubbish.

Some links for you to study up on CEMF ,and what it is.

http://www.electronics-tutorials.ws/inductor/inductance.html
Quote: Lenz's Law tells us that an induced emf generates a current in a direction which opposes the change in flux which caused the emf in the first place, the principal of action and reaction.

https://www.nde-ed.org/EducationResources/CommunityCollege/EddyCurrents/Physics/selfinductance.htm
Quote:  Lenz's law states that an induced current has a direction such that its magnetic field opposes the change in magnetic field that induced the current. This means that the current induced in a conductor will oppose the change in current that is causing the flux to change.

http://web.mit.edu/viz/EM/visualizations/coursenotes/modules/guide11.pdf
Kirchhoff's Loop Rule Modified for Inductors:
If an inductor is traversed in the direction of the current, the "potential change" is
−L d( / I dt). On the other hand, if the inductor is traversed in the direction opposite of the
current, the "potential change" is +L d( I / dt).

I can post a lot more links to info MH,if you are still stuck.


Brad

[tinman]

MH,

Tinman defined CEMF as follows:
Were I grading papers, I would merely have scratched out the words I highlighted in bold above, and replaced "the OPPOSITE direction" with the word "opposition" so that it reads "creates a current flow in _opposition_ to the current flow", just to clarify and be a bit more precise.

If I wanted to nitpick at it a bit further, I might also have circled "CEMF" and wrote "preferred" next to it, and possibly replaced the word "coil" where used with the word "conductor" (unless the question specifically asked about a coil, and not just a generic inductor).

I would also have been tempted to insert "flowing through it" in the first sentence so that it reads "the current _flowing through it_ will change from zero".

However, I would have given full credit for his response, as it demonstrates a basic grasp of the concept.

I know the two of you have been at odds for some time, but the rather demeaning nature of your response seems a bit much. 

PW

Thank you PW.

I am willing to lean,but i am not willing to let MH make me look like i have no idea as to what is going on here.
I would like to have good standing with those around me,but MH is doing his best to discredit that good standing,and i just cant sit back from that,and i dont believe you,Poynt,or anyone else would either.


Brad.

[MileHigh]

PW:

Yes, a coil will produce a CEMF when you connect a battery up to it.  And the true definition of CEMF is based on the rate of the changing current flowing through the coil.  But you kind of get in to a chicken and egg argument since it is the EMF from the battery itself that causes the changing current in the first place.  So is it "allowed" to say that the battery's EMF is the cause of the CEMF, being aware that if it is a real coil they won't be equal?

The bottom line is that it is the battery that causes current to flow into the coil, and any talk about the CEMF causing current to flow into the battery, tangible or hypothetical, is wrong.  We are talking about a simple single current loop here.

Brad can talk trash too, so don't always paint me as the "bad guy."  Reading his crazy theory was extremely disappointing to me.  It is what it is.

There is nothing wrong with making a very strong point sometimes, especially when it would appear almost nothing registered going the polite route for all these years.  You won't even tell him in simple terms that he is wrong sometimes, like you are going to faint or something.  Even though it is not your style, ultimately it's counter-productive for him.  If I didn't scrap with him, he would still be completely lost like he was at the beginning of this thread.  Direct talk sometimes has its merits.

In the final end game, if Brad is going to have his crazy theories, live and let live.  It's just a chat forum.

MileHigh