Magnet Myths and Misconceptions

tinman · January 21, 2015, 12:12:09 AM

Quote from: Pirate88179 on January 21, 2015, 12:05:42 AM
What about a piezo disk stuck between two neos? Will not the constant squeeze release some measurable output?

Bill

If it was just a matter of a constant squeeze needed to produce a constant output,we could just sit a house brick on the piezo. The piezo requires an osscilating pressure to produce power.

tinman · January 21, 2015, 12:17:32 AM

Quote from: tinman on January 21, 2015, 12:07:26 AM
Ok ,lets make this as simple as possable.
When we supply a DC current to a solenoid,is any of that input power used/consumed to create the magnetic field around that solenoid?

OK,i may have described this wrong by useing solenoid.
Lets make it an inductor insted to eliminate any moving parts that may impack on this thought experiment.

When a DC current is supplied to an inductor,is any of the input power consumed/used to create the magnetic field around that inductor,or is it all disipated as heat?.

2- Once the magnetic field around that inductor is astablished,dose it require any of the input power to that inductor to maintain that field,or is it all disipated as heat?

synchro1 · January 21, 2015, 12:20:37 AM

Quote from: MarkE on January 20, 2015, 11:53:56 PM
Two magnets with identical total magnetic field strengths: M can have very different abilities with respect to picking up / holding soft iron pieces, IE your armatures. By changing the winding permeability the field shape also changes.

TK's correct F=V/R. The obvious advantage to the steel windings is that even though it will take over 5x's the power to create an equal flux density as the copper, the steel windings will act as a permanent magnet after the power's disconnected. This could turn into a huge energy savings over time, depending on the VRM of the coil.

tinman · January 21, 2015, 12:24:50 AM

Quote from: synchro1 on January 21, 2015, 12:20:37 AM
TK's correct F=V/R. The obvious advantage to the steel windings is that even though it will take over 5x's the power to create an equal flux density as the copper,

Al sounds great on paper,but i wonder if it is fact in the real world?.

synchro1 · January 21, 2015, 12:33:35 AM

Quote from: tinman on January 21, 2015, 12:24:50 AM
Al sounds great on paper,but i wonder if it is fact in the real world?.

Ed Leedskalnin tested these kinds of coils. A short reverse pulse would completely neutralize the permanent field.