MH's ideal coil and voltage question

[minnie]

   I found this a bit of fun.
  YouTube "5,000 amp transformer" by photonicinduction.
      John.

[poynt99]

An ideal inductor sitting at rest, is essentially an ideal piece of wire. So when an ideal emf is placed across it, the current wants to instantly jump to infinity, right at t=0.

Due to the self-induced cemf however (the negative feedback), current is limited to rise at 0.8A/s (in our case with 4V and 5H).

There are two reasons the induced cemf = the applied emf:

1) The obvious reason is that the ideal voltage source is holding the inductor terminal voltage at 4V.

2) The not so obvious reason is due to the self-induction feedback process trying to be explained here.

To explain further, try thinking about the process right from the very beginning. As I said above, the moment Vin is applied, the current will try to instantly go to infinity. We know however that simultaneously, the inductor is self-inducing an opposing emf which is going to cause the current to increase at a set rate determined by Vin and L. This is the feedback mechanism that makes an inductor what it is. The inductor doesn't limit current, it limits the change in current. Any change in current is reflected in a corresponding opposing emf, which opposes the applied emf. In the case when R=0, the emf and cemf are always equal. The cemf settles or equalizes to the same value as the applied emf.

[picowatt]

An ideal inductor sitting at rest, is essentially an ideal piece of wire. So when an ideal emf is placed across it, the current wants to instantly jump to infinity, right at t=0.

Due to the self-induced cemf however (the negative feedback), current is limited to rise at 0.8A/s (in our case with 4V and 5H).

There are two reasons the induced cemf = the applied emf:

1) The obvious reason is that the ideal voltage source is holding the inductor terminal voltage at 4V.

2) The not so obvious reason is due to the self-induction feedback process trying to be explained here.

To explain further, try thinking about the process right from the very beginning. As I said above, the moment Vin is applied, the current will try to instantly go to infinity. We know however that simultaneously, the inductor is self-inducing an opposing emf which is going to cause the current to increase at a set rate determined by Vin and L. This is the feedback mechanism that makes an inductor what it is. The inductor doesn't limit current, it limits the change in current. Any change in current is reflected in a corresponding opposing emf, which opposes the applied emf. In the case when R=0, the emf and cemf are always equal. The cemf settles or equalizes to the same value as the applied emf.

.99,

I know I have just about exhausted every way I know how to explain the "rate of change" regulating mechanism of an inductor.  Perhaps the very concept of negative feedback needs to be explained. 

Do you see  anything in my last post to Partzman that I could word better to get the point across or make it more clear?

PW

[poynt99]

.99,

I know I have just about exhausted every way I know how to explain the "rate of change" regulating mechanism of an inductor.  Perhaps the very concept of negative feedback needs to be explained. 

Do you see  anything in my last post to Partzman that I could word better to get the point across or make it more clear?

PW

Absolutely not, your explanation and wording makes perfect sense to me.

I do however see the dilemma some may have when trying to get their heads around emf=cemf and current being able to flow. But again, I will refer them to a resistor across a voltage source. The two voltages are identical (i.e. KVL holds), yet current flows. I will also refer them to the fact that upon connection, ALL the voltage is across the inductance, in both real and ideal inductors, yet current begins to flow.

There may be a more scientific explanation to all this, I am just too dumb to muster it.

[picowatt]

Absolutely not, your explanation and wording makes perfect sense to me.

I do however see the dilemma some may have when trying to get their heads around emf=cemf and current being able to flow. But again, I will refer them to a resistor across a voltage source. The two voltages are identical (i.e. KVL holds), yet current flows. I will also refer them to the fact that upon connection, ALL the voltage is across the inductance, in both real and ideal inductors, yet current begins to flow.

There may be a more scientific explanation to all this, I am just too dumb to muster it.

Perhaps more like "too frustrated"...

I am hoping Partzman will eventually "get it" and then perhaps he will be able to explain it better to those that don't.

We shall see...

PW