MH's ideal coil and voltage question

[allcanadian]

@Magneticitist

I have actually always believed this and it's hard for me to think otherwise. [/size]I can't help it no matter how foolish it may seem.

Think of space, charges move producing a magnetic field and there is no resistance. Supposedly empty space conducts just like a vacuum tube thus in 99% of the universe a complete lack of resistance is in fact the norm.  The only problem with understanding nature seems to be human nature and their odd preoccupation with math, numbers and equations... the proverbial rabbit hole.


AC

[tinman]

Like any other inductor.
Indeed this question is germane to the original question, What is your answer?

How do you calculate the L/R time constant, when there is no R

My answer has already been posted--the current rise is instant-or at the speed of light-close enough,as there is no resistance to appose the current flow.

You posted a comment on th JT thread not long ago Poynt,and it was-- @T=0,one would think the universe would blow up.


Brad

[Pirate88179]

T=0 is The Big Bang.

Think about it.  There was no time prior to that event so it had to be 0.

Bill

[tinman]

You may wish to exercise a few examples to see if your conclusion is correct. Your conclusion being that if the time constant (Tau) is infinite, the load immediately presents itself as a perfect short, meaning the current will be infinite and instantaneous.

Here are a few: (in all cases, L=6H)

1) R=1, Tau=6s
2) R=0.1, Tau=60s (1min)
3) R=1m Ohm, Tau=60ks (16.6 hours)
4) R=1u Ohm, Tau=6M(million)s (1667 hours)
5) etc.

What is happening to Tau as R decreases?
If R could be 0, Tau must be infinite.
What happens to the inductor current after t=0 when Tau=infinity?

As i said before,if Tau is infinite,there is no inductance,and so there is nothing to create the BEMF that apposes the applied EMF,and so now the applied EMF is across a dead short,as an ideal inductor has no resistance.
This results in an instant current rise to an infinite value.


Brad

[tinman]

T=0 is The Big Bang.

Think about it.  There was no time prior to that event so it had to be 0.

Bill

The big bang at T=0 was the creation of the universe. Poynt said that the universe would blow up at T=0,meaning that the universe was already in existance.


Brad