hodges
National Hazard
Posts: 525
Registered: 17-12-2003
Location: Midwest
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Very Simple Battery Demo
I stumbled upon this idea while trying to come up with the simplest possible demonstration of an electric cell.
Magnesium by itself has enough electrical potential to light a red LED. Simply touch the negative lead of an LED to a piece of magnesium ribbon, and
touch the positive lead to either a carbon rod, or else a small piece of copper pipe fitting from the hardware store. When these plates are immersed
in salt water, the LED lights - brighter as the plates are immersed further. No need to fuss with multiple cells as is normally required when using
zinc.
I got slightly better results with the carbon rod than with the copper, but both work. I measured around 1.8 volts using the carbon rod and 1.7 volts
using the copper. Theoretically the copper should add a couple tenths of a volt to the cell whereas the carbon should be neutral. I suspect the
reason the carbon rod works better is either that the copper contains impurities that may have a negative vs. positive potential.
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Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
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Mood: Chemistry: the subtle science.
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Zn vs Cu
I once offered my services for "Engineers' Week" for one day at a local junior high school. I tried to tell the 8th grade students
what engineers do and what careers were available.
My demo for the class was very similar to yours except I used a sharpened 3/4" Cu pipe and a Zn coated strip of sheet metal for electrodes. I
pushed these into an orange to form the electrolyte bridge. I also lit a red LED, getting a little over a volt IIRC. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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Funkerman23
Hazard to Others
Posts: 416
Registered: 4-1-2012
Location: Dixie
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Quote: Originally posted by LanHarjochee  | | I want to buy these battery-operated LED fairy lights to drape over my wooden notice board or metal headboard. My parents say they will start a
fire... Do you think they would? Why/ why not? If yes, are there any lights that are similar that I can buy that aren't a fire hazard?
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Not a chance, those diodes( the LEDS) won't even get above room temp if ran at their rated voltages. and to
further this the voltages used to light the LEDs isn't anywhere near enough to create a hot enough spark. you'd blow out most of the diodes long
before and IF( and this is a big IF) there was a spark it wouldn't do much but catch your eye. In short there is no way that a led light string can do
much of anything except light up. How this relates to the OP I don't know.
[Edited on 4-5-2012 by Funkerman23]
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Agecer
Harmless
Posts: 5
Registered: 26-9-2012
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Mood: No Mood
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| Quote: Originally posted by Funkerman23 | | Quote: Originally posted by LanHarjochee | | I want to buy these battery-operated led tube to drape over my wooden notice board or metal headboard. My parents say they will start a fire... Do
you think they would? Why/ why not? If yes, are there any lights that are similar that I can buy that aren't a fire hazard?
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Not a chance, those diodes( the LEDS) won't even get above room temp if ran at their rated voltages. and to
further this the voltages used to light the LEDs isn't anywhere near enough to create a hot enough spark. you'd blow out most of the diodes long
before and IF( and this is a big IF) there was a spark it wouldn't do much but catch your eye. In short there is no way that a led light string can do
much of anything except light up. How this relates to the OP I don't know.
[Edited on 4-5-2012 by Funkerman23] |
I believe LED is the best technology when it comes to lighting
[Edited on 28-9-2012 by Agecer]
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