MH's ideal coil and voltage question

[MileHigh]

one thing that majorly confused me, and apparently you as well, was the 'ideal voltage' source also being a variable supply. so not only does this magic power supply provide infinite current with 0 vdrop it can change voltage at any time. I was under the impression an ideal vsource was a fixed source for all intents and purposes, though apparently not.

That's an ironic twist for you.  The supposedly "open-minded researchers that go where conventional scientists don't dare go" can sometimes be so closed-minded that they can't conceive of something as simple as an ideal voltage source that varies in time.

[Magneticitist]

That's an ironic twist for you.  The supposedly "open-minded researchers that go where conventional scientists don't dare go" can sometimes be so closed-minded that they can't conceive of something as simple as an ideal voltage source that varies in time.

it's quite simple.. having not invested any real time into learning about 'ideal' components, I had to look up what constituted an ideal voltage source.. The information I gathered stated an ideal voltage source was a fixed source that can supply infinite current without dropping.. Obviously that was an incorrect or incomplete description.
(i will say that yes, the possibility of a variable supply did indeed fly over my head. I won't cry about it!)
Now you're just being spiteful.

[MileHigh]

I'm not being sarcastic at all.

Unless I'm overlooking something, or don't correctly understand the question, there will be no current, and the voltage across the inductor will be whatever the voltage source is at any one time, from t=0 to the end of time.

Given that tau=infinity, there can be no change in either I or V. Indeed if R is non-zero, there will be a current and the voltage change over time.

I am going to have to assume that you don't understand the question.  Before t=0 the voltage source and the coil are disconnected.  The only reason for putting it that way is to implicitly establish that the current through the coil is zero at the start of the test.  At t=0 you then have a 4-volt source connected to a 5-Henry inductor, and then the voltage varies in time as described.

When it is reworded as above, is it clear now?

[poynt99]

Brad,

I don't support your answer regarding the inductor acting like an instantaneous short. Just because there is no current flow, doesn't mean the load presented to the voltage source is no longer "inductive".

There is only one answer, that being the inductor will essentially look like a perpetual "open" to the voltage source. At least that is my thinking on this until MH corrects me, and I welcome being corrected if I am in fact wrong on this.

[MileHigh]

it's quite simple.. having not invested any real time into learning about 'ideal' components, I had to look up what constituted an ideal voltage source.. The information I gathered stated an ideal voltage source was a fixed source that can supply infinite current without dropping.. Obviously that was an incorrect or incomplete description.

Now you're just being spiteful.

They say fixed source meaning that the voltage will not change under load.  They don't say anything else.