Basic inductor question

[M. Hamed]

How is it that the winding direction of a coil whether it is CW or CCW
has no effect on the direction of the induced voltgae. When we analyze
a circuit we always do v = Ldi/dt, however according to the right hand
rule, depending on the current direction, the field direction will
have one of two orientations.

Can someone shed a light on how this works?

 

[Nobody]

On Sun, 19 Sep 2010 12:35:33 -0700, M. Hamed wrote:

How is it that the winding direction of a coil whether it is CW or CCW
has no effect on the direction of the induced voltgae. When we analyze
a circuit we always do v = Ldi/dt, however according to the right hand
rule, depending on the current direction, the field direction will
have one of two orientations.

Can someone shed a light on how this works?

The winding direction "cancels out".

A current creates a field. A changing field creates a voltage.

If you change the winding direction, you negate both of the relationships,
resulting in no change overall.

 

[Michael Robinson]

"M. Hamed" <mhelshou@hotmail.com> wrote in message
news:ec35f188-a520-459a-96df-0c4faf40f937@t11g2000vbc.googlegroups.com...

How is it that the winding direction of a coil whether it is CW or CCW
has no effect on the direction of the induced voltgae. When we analyze
a circuit we always do v = Ldi/dt, however according to the right hand
rule, depending on the current direction, the field direction will
have one of two orientations.

Can someone shed a light on how this works?

Hello Hamed.
Imagine a pancake coil, grounded at the center with a positive voltage
applied to the outer lead.
You can pull the center out like a slinky in either direction. It won't
change the orientation of the magnetic lines.
Or say you are winding a toroid oriented with its axis vertical, and you
start by laying a wire over the top of the toroid, pulling it down through
the center and back toward you from underneath.
It then matters not whether you continue the windings leftward or rightward
around the toroid (this is the same statement, in principle, as the pancake
coil).
Looking at two toroids wound in this way, you would probably say they are
wound in opposite directions. But that ignores phasing. You have a dot at
the end of the wire you started with. If you now compare the two toroids,
INCLUDING THE PHASING DOT, you will see that they have the same handedness.

 

[whit3rd]

On Sep 19, 12:35 pm, "M. Hamed" <mhels...@hotmail.com> wrote:

How is it that the winding direction of a coil whether it is CW or CCW
has no effect on the direction of the induced voltgae. When we analyze
a circuit we always do v = Ldi/dt, however according to the right hand
rule, depending on the current direction, the field direction will
have one of two orientations.

Firstly, lets's get the nomenclature straight. CW and CCW refer to
a planar surface viewed from one side only; if you were behind a
transparent clock, the hands would move CCW as you watched.
In terms of a flat-wound coil, the difference between CW and CCW
includes the choice of which of the two terminals you 'start' from,
there's NO other meaning.

When looking at mutual inductors, the orientation of the magnetic
field does depend on the current injected, and does so by the
right-hand-rule (because we defined field direction that way).
So, there's a polarity change if you inject the current in one or the
other terminal, but it's the polarity of the FIELD (i.e. it's a three-
dimensional
vector, with orientation and magnitude). The 'V = L di/dt'
equation
doesn't have any field-vector orientation dependence.

The second winding of a transformer, though, DOES have an orientation
dependence, usually a polarity with respect to the primary winding.