P60 and P61

[Chris201W]

What's the physical difference between a P60 and a P61 lamp assembly? In other words, why does a P61 burn twice as bright as a P60?

 

[a99raptors]

Educated guess -

The filament causes a lot more resistance. With a lot more resistance, you get a filament that runs hotter because of "wasted" energy in overcoming that resistance. When the filament gets hotter, it lets out more light.

If memory serves me, there are several ways to change the resistance value. Among them, changing the diameter of the filament, using a different material, etc etc.

Problem with more resistance is that more energy is used up, accounting for the limited runtime.

For a more detailed explanation, I yield the floor to Dr. Peter Hauk

 

[tommymeboy]

I noticed that the P61 I just bought was frosted at the tip,whereas the P60 is not- perhaps that increases the spot size-?

 

[Flash_Gordon]

The filament resistance of the P61 is lower. If you have both, and a decent meter, you can measure this. Also, with a good magnifier, you can observe that the P60 filament is much longer. Since the reisistance of a lamp filament is much higher than typical copper wire, this length does make a large difference.

Since the battery voltage is constant, the lower resistance will cause a higher current flow. More emitted light but also much shorter runtime.

The frosting on the envelope tip has to do with beam quality and not output.

Mark

 

[Yooper]

Educated guess -

The filament causes a lot more resistance.

Actually that's backwards. V = I•R and P = I•V. More light = more power, and this requires more current. To pull more current at a given voltage, you need a filament with LESS resistance.

In layman's terms, a P61 siimply uses a higher wattage bulb than a P60. Think of a common household 100W incandescent bulb compared to a 60W.

The P60 and P61 bulbs are more complex than simple incandescents, with special gas mixes, etc., but that's the gist.

EDIT: Flash beat me to it. Must have posted while I was carefully typing and editing...

 

[a99raptors]

(That's me shooting myself....)

I stand corrected. Thanks for the clarifications!

Guess I shoulda attended those science classes more often.:ironic:

 

[Tremendo]

I put a P61 in one of my G2's, and it got used quite a bit a few nights ago. I'm surprised the batteries are still strong. I was concerned thinking it might drop down very quickly, due to the higher output, but that has not been the case. My P61 beam is bigger and brighter.