Carbon vs Graphite

[gary350]

I was reading where it says, graphite will conduct electricity, carbon will not.

I was reading another place where it says, search lights use carbon arc rods to produce carbon arc light.

Another place says, old movie projectors from the 20s and 30s used carbon arc light.

The welding shop sells carbon rods with a copper coating over the outside.

I found another place where it says, Coal is pure carbon.

I have a science experement that says, use pure carbon rods not graphite for the electrodes in this experement. Turn on the DC voltage the carbon rods will slowly be eaten away until they are gone. Bubbles will form in the salt water around each rod, hydrogen on one rod, oxygen on the other rod. Sodium Chloride will be converted to Sodium Chlorate which is an excellent weed and brush killer.

My question is. Is the science experement statement wrong? If carbon does not conduct electricity then how will it work?

 

[Joe G]

carbon and graphite both conduct, check the continuity of a pencil line and charcoal rub on paper, the resin (glue, binder) in some graphite or carbon items may be non conductive,

 

[alec_t]

Carbon is an element. Graphite is one physical form of carbon (diamond is another). Coal contains carbon but is definitely not pure carbon. Graphite conducts but diamond does not.

 

[squishy36]

Look up the term "allotropes". Different allotropes of carbon can have different physical behaviors. For example, graphite and diamond are both allotropes of carbon but have substantially different electrical conductivities -- graphite is a fairly good conductor with a resistivity of around 10 uohm*m, but diamond is considered an insulator because it has a resistivity 1e24 times higher. This comes about purely because the carbon atoms have different bonds in the two types of materials (they are both formed with nothing but carbon atoms).

 

[crutschow]

Carbon is an element. Graphite is one physical form of carbon (diamond is another). Coal contains carbon but is definitely not pure carbon. Graphite conducts but diamond does not.

Certainly coal is far from pure carbon. All the ash and cinders left over after you burn coal is the stuff that is not carbon.

 

[alec_t]

graphite is a fairly good conductor with a resistivity of around 10 uohm*m, but diamond is considered an insulator because it has a resistivity 1e24 times higher.

I'm glad you confirmed that. I stuck my Ohmmeter probes across the diamond in my wife's ring and was wondering if I'd been sold a lump of glass!

 

[Joe G]

"My question is. Is the science experement statement wrong? If carbon does not conduct electricity then how will it work? "
the rods from the weld shop should work, they are used frequently whilst stick welding when bridging gaps too wide to ark, you lay "worms" of weld over
them untill built up, they used to come in sizes from 1/8" and up.

 

[gary350]

When I was about 10 years old (51 yrs ago) a large 1.5 volt lantern battery had a carbon rod about 7/8" diameter 6" long inside. I wish I had a few of those.

D size batteries had 1/4" carbon rods once. The last time I cut open a battery several years ago there was no carbon rod.

 

[Joe G]

yea, some old books and how to's say about the rods in batterys, i havent seen them either since i was a kid. when i did need some here and there, i had to go to the
weld shop for them,

 

[shortbus=]

"My question is. Is the science experement statement wrong? If carbon does not conduct electricity then how will it work? "
the rods from the weld shop should work, they are used frequently whilst stick welding when bridging gaps too wide to ark, you lay "worms" of weld over
them untill built up, they used to come in sizes from 1/8" and up.

Never heard of that. The only thing ever saw done with those carbon rods was used in a 'carbon arc torch' to heat or braze with. Or the larger size used to 'air arc' to scarf a joint before welding or to cut cast iron.