[AMRadio] Extra Class isn't dumbed down? (was Viking 1)

Nick England navy.radio at gmail.com
Wed Dec 23 05:41:53 EST 2015

See Maxwell's equations but basically what Rob said. For an inductor
v=Ldi/dt. So current through an inductor is proportional to the integral
over time of the voltage.  The integral of a steady state sine wave is a
sine wave lagging by 90 degrees. For the first cycle you probably need
Laplace transforms to figure it out exactly but that course was a long time

On Tuesday, December 22, 2015, Jim Liles <hallicrafterssr2000 at k9axn.com>

> Hi Rob,
> I wasn't suggesting memorizing everything.  I suggested that we all
> memorize
> formulas and concepts not just newbies.  Now, because they may memorize
> more
> than others doesn't qualify them for target practice.
> Rob, your comment "Current lags in an inductor because the field is induced
> first but the bulk of the current doesn't flow until the field collapses"
> is
> not what I was looking for.
> The question that I ask is "How does the current get to the point that it
> lags the voltage by 90 degrees in an inductor?".
> That's a universally asked question by new comers to the hobby including
> myself 62 years ago as a Novice.
> Explain it using a single sine wave applied to an inductor; don't cloud the
> explanation with resistance, just inductance.  Don't worry about the
> values,
> explain how and at what time during that first cycle there is a 90 degree
> relationship: or any cycle after the first.
> Articulate the phase relationship at the end of each 1/4 cycle.
> I asked this because rote learned concepts do not necessarily mean there is
> understanding; but they are a good starting point.
> If this is of no interest to anyone simply erase it and I will simply
> evaporate.  Some may find it interesting.
> Kindest regards Jim K9AXN
> -----Original Message----- From: Rob Atkinson
> Sent: Tuesday, December 22, 2015 5:22 AM
> To: Jim Liles
> Cc: Discussion of AM Radio in the Amateur Service
> Subject: Re: [AMRadio] Extra Class isn't dumbed down? (was Viking 1)
> Current lags in an inductor because the field is induced first but the
> bulk of the current doesn't flow until the field collapses.
> you can't justify memorizing _everything_ because many have memorized
> math formulas.  Sorry, but that's a false analogy.  Try something
> else; good luck.
> 73 Merry Christmas
> Rob
> K5UJ
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Nick England K4NYW

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