I notice that inserting AAA cells vs. AA cells (both fit between the
contacts) of an LED flashing bicycle lamp, that the lamp seems
_brighter_ with the _smaller cells. At first this seems counter-
intuitive, but then I guessed this means that the larger cells,
unsurprisingly, have larger internal resistance, so the net current
draw through the circuit for fixed battery EMF really is larger for
the smaller cells.

Comments?

"Edward Green" wrote in message
...
I notice that inserting AAA cells vs. AA cells (both fit between the
contacts) of an LED flashing bicycle lamp, that the lamp seems
_brighter_ with the _smaller cells. At first this seems counter-
intuitive, but then I guessed this means that the larger cells,
unsurprisingly, have larger internal resistance, so the net current
draw through the circuit for fixed battery EMF really is larger for
the smaller cells.

Comments?
Sure. You guessed. Only an idiot would do that.

On Fri, 10 Oct 2008 16:01:53 -0700 (PDT), Edward Green
wrote:

I notice that inserting AAA cells vs. AA cells (both fit between the
contacts) of an LED flashing bicycle lamp, that the lamp seems
_brighter_ with the _smaller cells. At first this seems counter-
intuitive, but then I guessed this means that the larger cells,
unsurprisingly, have larger internal resistance, so the net current
draw through the circuit for fixed battery EMF really is larger for
the smaller cells.

Comments?

Larger cells have lower internal resistance. Were all cells brand new, of
the same type and from same manufacturer?

Did you measure the cell voltage under load (in the flasher)?

--
Boris

On Oct 11, 12:01*pm, Edward Green wrote:
I notice that inserting AAA cells vs. AA cells (both fit between the
contacts) of an LED flashing bicycle lamp, that the lamp seems
_brighter_ with the _smaller cells. *At first this seems counter-
intuitive, but then I guessed this means that the larger cells,
unsurprisingly, have larger internal resistance, so the net current
draw through the circuit for fixed battery EMF really is larger for
the smaller cells.

Comments?

Internal resistance can be ignored unless the load is in itself of
comparable size. Suppose the internal resistance was 0.1 Ohm then we
could assume that a load of 1 ohm upwards would have little effect.
This is called a "stiff" voltage source. What is the series
resistance of your LED circuit? Normally around 330 Ohms for a 5v
supply so it would make no difference.
(from an Electrical Engineer - not a poofy Physicist)

Hardy

On Oct 11, 1:28*am, Benj wrote:
On Oct 10, 7:01 pm, Edward Green wrote:

I notice that inserting AAA cells vs. AA cells (both fit between the
contacts) of an LED flashing bicycle lamp, that the lamp seems
_brighter_ with the _smaller cells. *At first this seems counter-
intuitive, but then I guessed this means that the larger cells,
unsurprisingly, have larger internal resistance, so the net current
draw through the circuit for fixed battery EMF really is larger for
the smaller cells.

Comments?

Sure. Understanding usually requires information. You haven't supplied
much.

1. it's interesting that both batteries fit the contacts given that AA
batteries are about 1/4" shorter than AAA batteries.

Long contact springs (and I think you meant the other way around).

2. you don't say whether all batteries are of the same type and brand
and are brand new. this is crucial for a meaningful comparison.

True. All were NICAD, but the AAA were not brand new.

3. Since you don't have a clue as to the "flasher" circuit, you can't
deduce in any what just WHICH property of the battery is controlling
the "apparent" brightness. For all you know it might be the voltage
instead of internal resistance.

4. There are a number of physiological optical effects with flashing
lights controlling what you PERCEIVE as brightness which may or may
not relate to actually integrated brightness. These include pulse
width and peak luminosity.

5. None of your conclusions can be deduced from the data.

Guilty as charged, Guv'nr.

On Oct 10, 3:01*pm, Edward Green wrote:
I notice that inserting AAA cells vs. AA cells (both fit between the
contacts) of an LED flashing bicycle lamp, that the lamp seems
_brighter_ with the _smaller cells. *At first this seems counter-
intuitive, but then I guessed this means that the larger cells,
unsurprisingly, have larger internal resistance, so the net current
draw through the circuit for fixed battery EMF really is larger for
the smaller cells.

Comments?

Having the cells but not the multimeter handy makes me pose it like
this.

Diodes emit light as a function of voltage, not current. If the light
is quantitatively brighter, then you should find that the AAA cells
have a slightly higher average voltage than the AA cells.

On Oct 10, 3:14*pm, "Androcles" wrote:
"Edward Green" wrote in message

...I notice that inserting AAA cells vs. AA cells (both fit between the
contacts) of an LED flashing bicycle lamp, that the lamp seems
_brighter_ with the _smaller cells. *At first this seems counter-
intuitive, but then I guessed this means that the larger cells,
unsurprisingly, have larger internal resistance, so the net current
draw through the circuit for fixed battery EMF really is larger for
the smaller cells.

Comments?

Sure. You guessed. *Only an idiot would do that.

Let me pose the question in case you are even listening.

Why the **** do you even post when nonsense like this is your only
product?

On Oct 11, 1:25*pm, Eric Gisse wrote:
On Oct 10, 3:01*pm, Edward Green wrote:

I notice that inserting AAA cells vs. AA cells (both fit between the
contacts) of an LED flashing bicycle lamp, that the lamp seems
_brighter_ with the _smaller cells. *At first this seems counter-
intuitive, but then I guessed this means that the larger cells,
unsurprisingly, have larger internal resistance, so the net current
draw through the circuit for fixed battery EMF really is larger for
the smaller cells.

Comments?

Having the cells but not the multimeter handy makes me pose it like
this.

Diodes emit light as a function of voltage, not current. If the light
is quantitatively brighter, then you should find that the AAA cells
have a slightly higher average voltage than the AA cells.

Well, that is consistent with my conjecture, assuming the cells have
equal EMF, but that the AAA cells have lower internal resistance
(hence less voltage drop when a given current is flowing) -- although
one person disputes the last premise, and others say the effect should
be trivial given the relative magnitudes of internal resistance and
resistance of the circuit.

But basically Benj was right ... I have no clue about the important
parameters. Just passing time.

Eric Gisse wrote:
On Oct 10, 3:14 pm, "Androcles" wrote:

"Edward Green" wrote in message

...I notice that inserting AAA cells vs. AA cells (both fit between the

contacts) of an LED flashing bicycle lamp, that the lamp seems
_brighter_ with the _smaller cells. At first this seems counter-
intuitive, but then I guessed this means that the larger cells,
unsurprisingly, have larger internal resistance, so the net current
draw through the circuit for fixed battery EMF really is larger for
the smaller cells.

Comments?

Sure. You guessed. Only an idiot would do that.


Let me pose the question in case you are even listening.

Why the **** do you even post when nonsense like this is your only
product?

His daughter died.

I know it doesn't help us on this group, but it may explain his seeking
an outlet. Tough on us? maybe; but not half as tough as it has been for him.

On Oct 11, 4:59*pm, Phil the Farmer
wrote:
Eric Gisse wrote:
On Oct 10, 3:14 pm, "Androcles" wrote:

"Edward Green" wrote in message

....Inot ice that inserting AAA cells vs. AA cells (both fit between the

contacts) of an LED flashing bicycle lamp, that the lamp seems
_brighter_ with the _smaller cells. *At first this seems counter-
intuitive, but then I guessed this means that the larger cells,
unsurprisingly, have larger internal resistance, so the net current
draw through the circuit for fixed battery EMF really is larger for
the smaller cells.

Comments?

Sure. You guessed. *Only an idiot would do that.

Let me pose the question in case you are even listening.

Why the **** do you even post when nonsense like this is your only
product?

His daughter died.

I know it doesn't help us on this group, but it may explain his seeking
an outlet. Tough on us? maybe; but not half as tough as it has been for him.

He has been acting like a **** on this newsgroup years before his
daughter died.