Re: superposition

[Ludwik Kowalski <kowalskil@MAIL.MONTCLAIR.EDU>]

The same objection can then be made for the
example of two coils on an iron rod. Right?

One coil alone produces B1 (in the iron rode
they share) and another coil alone produces
B2. Acting together they produce B < B1+B2.
In my mind this is a good example in which
the superposition principle does not apply.
Ludwik Kowalski


On February 26, 2004, Edmiston, Mike wrote:

> Ludwik's example (below) is interesting.
> It depends upon what you mean by "adding
> two things" together. As stated, when
> viewing the light output with one battery,
> then the other battery, then both batteries,
> the result falls into the category I call
> synergism.  The light output with both
> batteries is more than the sum of the light
> outputs when each battery is used alone.
>
> However, one might argue you're not
> really adding the two effects together.
> To do that you would have two batteries
> and two lights.  You would measure the
> light from one battery-bulb combination
> (L1), then measure the light from the
> second battery-bulb combination (L2),
> and then measure the light with both
> bulbs lighted (LS  summed light).
> In this case superposition would hold...
>    L1 + L2=LS
>
> I like this example because it is easy to
> describe and also easy to demonstrate.
> However, if I were to use it in my teaching,
> I would be inclined to demonstrate both
> cases.  If I use Ludwik's example only,
> my "less-bright" students might conclude
> combinations of light do not follow the
> superposition principle.
>
>
> > Ludwik said...
> > Another example: two electric batteries, B1 and B2, in series with a
> > small light bulb. Each battery alone produces very small "amount of
> > light."  But together they produce A which is much larger than A1+A2.
> > Most people have experience with flash light sources. They know
> > that one battery will produce much much less than 50% of light one
> > gets from the normal set of two batteries.