How to Measure the Electrical Conductivity of Steel
Electrical conductivity represents the ability of a material to conduct electricity. In the case of metals such as steel, the electrons on iron atoms can migrate to adjacent atoms. As such, an electrical current -- which simply represents the flow of electrons -- can transfer from one end of a wire to the other. The ability of any metallic sample to conduct electricity depends on the inherent conductivity of the metal, the length over which the electrons transport and the cross-sectional area of the conductor. In practical terms, this means that some metals conduct better than others; copper metal, for example, conducts better than aluminum, all other factors being equal. It also means that long wires exhibit lower conductivity that short wires, and large-diameter wires exhibit better conductivity than small-diameter wires. Conductivity measures account for all of these factors, as can be seen in the equation for conductivity: C = L / RA, where C represents conductivity in units of Siemens per centimeter, L represents the length of the conductor in centimeters, R is the resistance of the sample in ohms and A is the conductor's cross-sectional area in square centimeters.
Other People Are Reading
Things You'll Need
- Steel wire or cylinder. 1 to 6 inches long
- Calipers
- Calculator
- Multimeter
Instructions
-
Measurements
-
1
Cut a sample of the steel to prepare for measurement. Ideally, the sample should be in the shape of a cylinder about 6 inches in length. The diameter is not as important, as long as it does not exceed 1 inch. A sample of wire works well for this purpose.
-
2
Measure both the diameter (D), and length (L), of the sample using a set of calipers and record the dimensions in units of centimeters. If the calipers only measure in inches, then multiply the measurement in inches by 2.54 to convert to centimeters.
-
-
3
Place the wire on a nonconducting surface, such as a wooden table. Turn on the multimeter and set it to measure resistance in ohms. Touch the probes to opposite ends of the wire or cylinder and allow the reading on the meter to stabilize. Record this value as resistance.
Calculations
-
4
Determine the radius (r), of the wire or cylinder by dividing the measured diameter, D, by two. A diameter of 0.48 cm, for example, would give r = D / 2 = 0.48 / 2 = 0.24 cm.
-
5
Calculate the cross-sectional area, A, of the wire or cylinder according to A = pi * r^2r. Continuing the example from Step 1, A = 3.14 * (0.24 cm)^2 = 0.18 cm^2.
-
6
Find the conductivity, C, of the sample according to C = L / RA. If the sample discussed in steps 1 and 2 was 10.40 cm in length and the resistance measured 6.0 x 10^-4 ohms, then C = 10.40 / (6.0 x 10^-4 * 0.18) = 9.6 x 10^4 Siemens per centimeter, or S/cm.
-
1
