The Physics
Factbook
An encyclopedia of scientific essays

Resistivity of Carbon, Amorphous

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Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Serway, Raymond A., and Jerry S. Faugh. College Physics. 6th Edition. Belmont, CA: Thomson, 2003.
Material Resistivity Temp. Coeff. of Resistivity
Ωm [(°C)-1]  
Carbon 3.5 × 10−5 -0.5 × 10−13
3.5 × 10−5 Ωm
Resistivity. Stransfield, Alfred. The Electric Furnace: Its Construction, Operation and Uses. New York: McGraw-Hill, 1914.
Resistivity of Solid Carbon [Ωcm]
Cold Hot
0.00124-0.00163 about 0.0010
1.24–1.63 × 10−5 Ωm
(cold)
1.00 × 10−5 Ωm
(hot)
Fink, Donald G., and H. Wayne Beaty. Standard Handbook for Electrical Engineers. 11th. New York: McGraw-Hill, 1978.
Material Electrical Resistivity at 20 °C in Ωcm
Carbon 0.0035-0.0046
3.5–4.6 × 10−5 Ωm
Resistivity of Amorphous Carbon. Rothwell, Richard Pennefather. The Mineral Industry. New York: Scientific Publishing, 1903. "The specific resistance of the artificial material is 0.00032 ohms per cu. in., or about one-fourth that of amorphous carbon (Rothwell 352)." 3.25 × 10−5 Ωm
Resistivity. Stransfield, Alfred. The Electric Furnace: Its Construction, Operation and Uses. New York: McGraw-Hill, 1914.
Electrical Resistivity of Amorphous Carbon
at Certain Temperatures
Temperature Resistivity [Ωcm]
10 °C 1.63 × 10−3
61 °C 1.60 × 10−3
466 °C 1.50 × 10−3
1.50–1.63 × 10−5 Ωm

The formula for resistivity is:

R = ρL/A

Where

R = Electrical Resistance
ρ = "rho", static resistivity measured in Ωmeters
L = length
A = cross-sectional area.

In both physics and chemistry, amorphous carbon is the name used for carbon that does not have any sort of crystal structure. As with all glassy materials, some short-range order can be seen, but there is no long-range pattern. Amorphous carbon is often abbreviated to a-C for general amorphous carbon. In its amorphous form, carbon is basically graphite but not held in a crystalline macrostructure and is found in powder form. The amorphous forms include black soot (also known as lampblack), gas black, and channel black or carbon black, which is used to make inks, paints and rubber products. It can also be pressed into shapes and is used to form the cores of most dry cell batteries and other related things. Amorphous carbon is formed when a material containing carbon is burned without enough oxygen for it to burn completely. Carbons of different forms are widely used in electrochemistry. This is because they meet the conditions set on electrode materials, such as their means of accumulating an electric charge, having a good electrical and thermal conductance, a large inner area, and showing a substantial resistance against the aggressive action of electrolytes. Amorphous carbon exhibits an inverse relationship between resistivity and temperature. It is also the inverse of conductivity. As the electrical resistivity and thermal resistivity decrease, the temperature increases, and vice versa.The electrical resistivity of amorphous carbon generally ranges from 1.5 to 4.5 × 10−5 Ωm.

The linear relation between resistivity and temperature can be stated as:

ρ1 = ρ2[1 + α(T1-T2)]

Where

ρ1 = resistivity value adjusted to T1
ρ2 = resistivity value known or measured at temperature T2
α = Temperature coefficient
T1 = Temperature at which resistivity value needs to be known
T2 = Temperature at which known or measured value was obtained

Dana Klavansky-- 2007