Measurement of the resistivity of the material of a wire The resistivity (r)of a material is one of the factors that determines the resistance of that material to the flow of electric current through it. In this experiment you measure the resistance (R) of a length of nichrome wire (length l) using an ohmmeter. You then measure the diameter (d ) of the wire using a micrometer screw guage. The resistance is given by the formula: R = rl / A, where A is the crosssectional area of the wire (A = p3r squared). The resistivity can be calculated from the formula: r = RA / l 




