MH's ideal coil and voltage question

[SeaMonkey]

...like a drunk[en] sailor?

Aye, to you Land-Lubbers it is just an expression.

To those of us who crewed the "haze gray and underway"
men o' war it was a way of life.  Extended periods at sea
develop quite a thirst in the Sailor and when finally in
port to enjoy some "Liberty" sipping the brew was a joyous
relief.

Naturally, too much of the brew leads to some really
odd behaviors which the Sailor is naturally inclined to
indulge in.  Hence, the expression of the Land-Lubbers.

Sailors are not offended by the expression.

[MileHigh]

2nd- As i have already tried to explain to you,i do not agree that the formula being used is correct from T=5 seconds to T=7 seconds.

Brad

Please tell us in your own words what the formula means.

[partzman]

I have taken the liberty of changing MH's original problem sightly so there is now a period following T3 to T5 from T5 to T8 with -4 volts applied to the 5H inductor. This is equal to but opposite the initial T0 to T3 so we can now see what happens to the inductor current.

One might find it easier to visualize the magnetic field around the inductor and how it varies in relation to the current.  I've included an algebraic proof of this relationship.

      𝑬𝒎𝒇 = - 𝑵 × 𝚫𝚽/𝚫𝒕    (Faraday's Law)
      𝑬𝒎𝒇 = - 𝑳 × 𝚫𝑰∕𝚫𝒕       (Inductance defined in terms of Emf)
      ∴ 𝑵 × 𝚫𝚽/𝚫𝒕 = 𝑳 × 𝚫𝑰∕𝚫𝒕   (Substitution)
      ∴ 𝑵 × 𝚫𝚽 = 𝑳 × 𝚫𝑰   (Reduce)
      ∴ 𝑳 = 𝑵 × 𝚫𝚽∕𝚫𝑰      (Inductance in terms of flux)
      ∴ 𝚫𝚽 = 𝑳 × 𝚫𝑰           (Flux over time verses inductance and current over time with 1 turn)

partzman

edit

[partzman]

Thank you Partzman,

So the input to spin up the flywheel is the same as is required to stop it.

Yes, in that analogy you are correct.

partzman

[verpies]

In spirit of the thread lets consider an ideal ferromagnetic as a break from the ideal voltage sources.
What properties would such material have?

For sure it wold not exhibit any hysteresis loss and it would not heat up at all when immersed in a changing magnetic flux.
It would not conduct electric current at all so Eddy currents could not form in it.
Would it have infinite permeability? - I don't think so, anymore than an ideal inductor needs to have an infinite inductance.

What are your thoughts?
What other properties would an ideal ferromagnetic have?