How does a flashlight work?

[SilverFox]

Hello Daniel,

Pitzl makes head lamps. One of the complaints against their design is that it is not water proof. I seem to remember a representative of Pitzl stating that when they put on a presentation, they take their head lamps, turn them on, and drop them into a fish bowl full of water. The lights remain on. After the presentation, they simply shake the water out of them and go on.

I also recall someone flooding a SF E1e or E2e and it still continued to work without problems, and someone else changed the battery in an ARC light underwater.

If water causes the battery to discharge, it must be a very slow process. The only mess involved was drying the light out afterwards to prevent corrosion.

I suppose if someone was concerned with this they could do a test. Drop a battery (or batteries) into a glass of water and check it after a period of time.

Tom

 

[cheesehead]

[ QUOTE ]
Harrkev said:
Plus, old copper is kind of nasty to handle. It tends to corrode. Yuk.

[/ QUOTE ]

Aluminum corrodes more than copper Copper gutters last for decades, aluminum if it's not treated will turn into mush in a few years, at most.

 

[gadget_lover]

[ QUOTE ]
SilverFox said:
Hello Daniel,

Pitzl makes head lamps. One of the complaints against their design is that it is not water proof. I seem to remember a representative of Pitzl stating that when they put on a presentation, they take their head lamps, turn them on, and drop them into a fish bowl full of water. The lights remain on. After the presentation, they simply shake the water out of them and go on.

I also recall someone flooding a SF E1e or E2e and it still continued to work without problems, and someone else changed the battery in an ARC light underwater.

If water causes the battery to discharge, it must be a very slow process. The only mess involved was drying the light out afterwards to prevent corrosion.

I suppose if someone was concerned with this they could do a test. Drop a battery (or batteries) into a glass of water and check it after a period of time.

Tom

[/ QUOTE ]

The important part is that it's a very slow process. 3 volts in a bucket of clear water will have only milliamps of drain.

The demonstration is a great marketing trick, but I'll bet they use a new one every time. Over time, the copper or brass will corrode. They may or may not have used distilled water to minimize the chances of problems. Next time, ask them to drop it in salt water for 1/2 an hour. /ubbthreads/images/graemlins/smile.gif

The closer the anode and cathode and the more impurities in the water the more the current will flow. Let if flow long enough and you see the corrosion from the electrolysis, the batteries discharge and you see all the problems that go with that.

Note that you can change the ARC AAA underwater because the electronics are sealed in epoxy. The battery tube should still be cleaned out at the earliest convenience.

It's important to note the difference between a high resistance short and a dead short. A dead short will divert all electricity back to the source. A high resistance short will divert only part of the electricity, causing many different symptoms, depending on where the short is and the nature of the circuit.

Daniel

 

[SilverFox]

Hello Daniel,

From what I recall, the water was tap water, the lights are mostly plastic, and they gave away the lights after the presentation.

I believe the purpose of the demonstration was to show that the lights would continue to function if you happen to be caught out in the rain.

Tom