Re: Coil EMF volt vs current

MooseFET wrote:
On May 3, 7:27 pm, John Larkin
<jjlar...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
On Thu, 03 May 2007 22:05:01 -0400, BFoelsch

Holding current constant, we can find the rate that power and the
field increases with N.

Scaling arguments--fun.

<=> is proportional to.

P = I^2 * R <=> N^2

Field <=> integral(1/N) <=> ln(N)

Therefor for a very thick coil:

Field/P <=> ln(N)/ N^2


This assumes that the core is a small perturbation on the inductance of one turn at the outer edge, which is true for open cores but not for closed ones. For closed-loop cores, the field is determined by the total current threading the loop. Position doesn't matter, at least not until order (iirc) 1/mu**2. If "solenoid" here has the physicsy meaning of "a coil wound like a Miniductor", this is true, but if it means "a push-pull magnetic actuator whose magnetic circuit is nearly closed at all times" then it isn't.

Cheers,

Phil Hobbs
.