MH's ideal coil and voltage question

[tinman]

There is no "potential difference" with a resistor yet current flows.

If there is no potential difference across a resistor,current will not flow through it--or did i miss something here?

Brad, IK is not the same as cemf or bemf.

IK is BackEMF.
All three are the result of the same action--a magnetic fields change over time,where the value is determined by the !rate! of change over time--among other things.

With standard feedback in amplifiers, even with 100% feedback the signal passes through at unity gain. Something to think about perhaps.

As the coil is ideal,then any energy put into that coil,should be returned,as an ideal coil cannot dissipate energy. So for example,if we put 100 joules of energy into that coil,we should get 100 joules of energy back out of that coil--one way,by IK collection.
Dose that sound right?


Brad

[tinman]

Some quotes by MarkE

1-That is correct.  BEMF resists changes in the current that any applied voltage attempts to drive.

2-Eddy currents induce voltage that opposes the driving voltage.  They are about resisting current changes.

3-Generator BEMF is not inductive kickback.  But inductive kickback is definitely BEMF.

4-BEMF is very simple:  It is the EMF that results from changing magnetic flux crossing perpendicular to a conductor that acts in opposition to the applied voltage across the length of the conductor.

So from what i understand,is IK BackEMF,and BackEMF/CEMF are only set apart as IK is a separate function to that of motor BackEMF and CEMF,but although the function is separate,the function that gave rise to the IK is still the same--a magnetic fields change in time.


Brad

[poynt99]

If there is no potential difference across a resistor,current will not flow through it--or did i miss something here?

I presumed, perhaps incorrectly, that when you referred to "potential difference" you meant the difference between the emf and cemf. Was I wrong? If not, then replace the inductor with a resistor, now you have the same voltage across the voltage source as the resistor, yet current flows.

IK is BackEMF.
All three are the result of the same action--a magnetic fields change over time,where the value is determined by the !rate! of change over time--among other things.

IK generally refers to the terminal voltage when an energized inductor goes open.

As the coil is ideal,then any energy put into that coil,should be returned,as an ideal coil cannot dissipate energy. So for example,if we put 100 joules of energy into that coil,we should get 100 joules of energy back out of that coil--one way,by IK collection.
Dose that sound right?

Sure.

[tinman]

A good net search reveals all of this...we have been up and down this road for years....whats next....Is this leading up to something?  Doesn't feel like it is....


When is the perspective going to change so that folk can begin discussing something that leads to something practical?




Regards

Something is all screwed up Erfinder.
Seems now there is to much debating what is and what is not,and far less time building and research on the bench.

It seems the more you learn,the less things make sense.

Think im going back to the !old days!,and let my bench do the talking.
I dont even know why im here,talking about a situation that dose not exist
I went further forward just building and testing,that i ever have discussing that which dose not exist.

Anyway, a few new exciting devices coming up,and a couple that i have already started on-->and one big one hiding in the background,near completion

In saying that,do you know how to cut Tungsten carbide ?


Brad

[partzman]

Regarding the Emf (applied voltage) equaling the Cemf (induced counter-emf) in an inductor with the analogy of an amplifier with feedback raises some questions IMO. Having designed, built, and manufactured many types of amplifiers with various types of feedback loops thru the years, they all have a common summing point somewhere in the circuitry. This summing point is actually a current node where the input and inverted output voltages are converted to opposing currents in ratios to yield an overall amplifier gain that one desires. The higher the open loop gain, the more accurate the designed gain.

This all seems to fit our Emf=Cemf situation at first glance but I would like to know "where is the summing point" in a single inductor? If it exists it should be able to be shown mathematically.

We know that Emf (applied voltage to a coil) = L*dI/dt as we can easily prove this with experimentation. We can rearrange the formula to solve for any unknown variable with the remaining known factors, so we are again assured this formula is correct.

We also know that Lenz dictates that with an "induced" current, Cemf = -L*dI/dt and this again can be proven experimentally.

What is difficult for me to accept and understand is to say the the Emf=Cemf in a single inductor with a voltage applied for if they are equal mathematically, they cancel mathematically and no current flows. I have to agree with TM on this. I would be happy to see mathematical proof to the contrary.

The current in an inductor is in phase with the applied voltage to the inductor which fits the Emf equation above and this would seem to indicate that the EMF wins in the production of output current over the Cemf. If the two are in a feedback interaction as the amplifier analogy implies, what is the ratio that would produce these results? What magnitudes or Emf and Cemf would have to exist to satisfy the EMF equation? IMO, Cemf would have to equal zero or the equation is invalid!

So, IMO Cemf does not exist in a single inductor but Cmmf does as I posted earlier.

pm