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Saltwater and light bulbs

by mutzy188
Tags: bulbs, light, saltwater
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mutzy188
#1
Feb4-05, 05:15 PM
P: 37
Hi everyone. Today in chemistry we saw this really cool video about different chemical reactions and learned that saltwater conducts electricity . I have one of those light bulbs that came out of a flashlight and it has 2 wires coming out of it. If I had some saltwater and stuck the wires of the bulb in the water would the bulb light? would I get electrocuted? If so how can I do this so I won't get electrocuted? Also does anyone know how much power saltwater produces?

~Thanks
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Integral
#2
Feb4-05, 05:55 PM
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To light the bulb you need a current, this means there must be a potential difference across the leads of the bulb. Sticking the bulbs in salt water does not imply a potential difference. Quite the opposite since the salt water is a good conductor, the leads will be at very nearly the same potential. Similar to connecting a wire directly from one lead to the other, this is not how you light the bulb.

Now, If you were to place 1 lead in salt water and connect the other to a battery. You could light the bulb by putting the OTHER side of the battery in the water.

Likewise, if you are in salt water holding one side of the battery (or some other power source) and the other side of the source is connected to the salt water you will become part of the circuit, under the right (wrong?) conditions this can be fatal.
mutzy188
#3
Feb4-05, 06:00 PM
P: 37
Is there a way I can make the saltwater like a battery? Can I make it so the saltwater powers stuff?

brewnog
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Feb4-05, 07:06 PM
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Saltwater and light bulbs

Integral, I think what mutzy's seen is a galvanic cell.

Mutzy, you can (theoretically) light your bulb!

Well, almost. If you connect one wire to a copper plate, and the other to a zinc plate, and dip those in the water, you'll have created a galvanic cell. It's not actually the saltwater itself providing the electricity, it's the difference in what's called the "electrode potentials" of the two (dissimilar) metals you use as "electrodes". You'll have made a very simple battery.

You won't get electrocuted, (if I've understood you right and you're not using any other power source) and because such a low current is generated you will probably struggle to even light a bulb. You might have seen "potato clocks" for sale in toy shops; this is how they work except they use potatoes instead of saltwater. I will point out again that the energy is NOT coming from the potato/salt water/copper sulphate solution/electrolyte.


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