MH's ideal coil and voltage question

[MileHigh]

No
figure 3 represents your circuit.

Replace your ideal voltage source with an ideal capacitor,and you have the same.
an ideal capacitor is your voltage source,where that ideal capacitor has no series resistance.
You charge your capacitor to 4 volts,and you place it across your ideal coil.
Can you now measure a voltage anywhere around that circuit,even though current is now flowing through it?.


Brad

No I assure you that figure 2 represents my circuit.

[poynt99]

If it has no internal resistance through that ideal voltage source,how can it not be a short circuit?

If it has 0V across it, then yes it is equivalent to a short circuit. However, this is a voltage source that starts out with +4V across it, therefore it must be drawn as an ideal voltage source or function generator.

Please post a diagram you !your! ideal voltage source.

It is a voltage source (set to voltage X) with a series resistor equaling 0 Ohms.

This is the paradox i am referring to,and why an ideal voltage source cannot exist,and/or be placed across an ideal inductor.

There is no paradox. You are misinterpreting an ideal voltage source as a zero Ohm wire. That is not the case unless as I said, the voltage is set to 0V.

What would happen if we reduced the internal resistance of a charged cap(say 1000uF with 10 volts across it) to a value of 0 ?.

You would have a good quality capacitor. What would happen? Nothing if it wasn't connected to anything. If connected to some load it would happily discharge.

[tinman]

Verpies, this is mass confusion day.  I find your figure 3 confusing.  If we view a shorted ideal coil like a classic toroidal inductor, then aren't we talking about putting a voltage source across the toroid such that it ends up looking like two separate coils in parallel?

If that is the case, I fail to see any utility in that.

(sorry for the chicken scratchings drawing.)

Well they wont be two seperate coils in parallel MH,because one winding will be CW and the other CCW.
So they will be in series,not parallel


Brad

[verpies]

Verpies, this is mass confusion day.

I kind of like it because it stimulates us to think.
I think this discussion is beneficial to all involved as long as Ad Hominem remarks are absent.

I find your figure 3 confusing.  If we view a shorted ideal coil like a classic toroidal inductor, then aren't we talking about putting a voltage source across the toroid such that it ends up looking like two separate coils in parallel?

The confusion will disappear immediately when you consider the coupling coefficient (k) between these two "separate coils" connected "in parallel".

In an ideal toroid the flux is completly shared and k=-1, thus in fact these coils are connected in anti-parallel when flux direction is considered. Thus they do not posses any inductance collectively. Consequently their anti-parallel combination possesses zero reactance and zero resistance, leading to zero impedance and the current flowing through the voltage source rises immediately to infinity.

If that is the case, I fail to see any utility in that.

It is pretty useless from an engineering standpoint, but it has a great educational value.
Anyway, it is what Tinman was referring to all along while you were apparently analyzing Fig.2.

[poynt99]

In that case:
Current (i) flowing through the inductor equals i=ΔΦ/1H and the current flowing trough the voltage source is infinite.

Now there is your paradox Brad.

When you place an ideal voltage source across an ideal short, who wins? The voltage source or the ideal wire? verpies seems to indicate that the voltage source wins, as the voltage holds and the inductor still gets some current.