Magnet Myths and Misconceptions

[MarkE]

Well, assuming an ideal source with limitless current capability, what would be the final current in a 1H ideal inductor with an ideal 1V DC supply applied? And how much energy would have been required?

If that doesn't mess with your mind, I don't know what would. 

The energy increases without bound as: 0.5*V²*T²/L

[MileHigh]

Just for fun and a reminder:  The challenge is out there to any of you to take a copper-wire coil and a physically identical iron-wire coil and measure the inductance for each coil without using an idiot box.  Just use your brains and the standard bench equipment that most of you have.  This is the Revenge of the Nerds - Bench Version.

[tinman]

For the same reason that it takes energy to accelerate a mass, but in the absence of friction none to maintain the mass' velocity.Yep.

So were kicking the football in space.

[MarkE]

So were kicking the football in space.

We are noting that there are other physical phenomena where it takes energy to change a state and once the state is changed additional energy is not required to maintain the new state:

Changing the kinetic energy of a mass in  frictionless environment.
Changing the electrostatic energy of a leakage free capacitor.
Changing the gravitational potential energy of an orbiting satellite in a frictionless environment.
Changing the gravitational potential of fluid in a reservoir that doesn't overflow.
Changing the bonding energy in molecules by way of an oxidation-reduction reaction.
Changing the magnetic field of a hard permanent magnet past its saturation point.
Changing the magnetic field of a superconducting electro magnet.

[MileHigh]

I often use the analogy of a flywheel for an inductor.  Since a flywheel is just mass in motion, then linear motion (like a football or a glider moving down an air track) is also a perfectly valid analogy for an inductor.

When you think of discharging an inductor it normally just loses all of its stored energy, end of story.  So if you can imagine that the glider on the air track crashes into a lump of putty at the end of the track so there is no bounce-back, that's like a discharging inductor.  The putty will get hot from absorbing the crash energy just like the resistor will get hot.

The second attached graphic shows an air track set up to act like an LC resonator.