A Figure 1: For a uniform cylindrical wire with cross-section area 2 of 3 A, length L and resistivity p, the resistance R is given as above. (Picture taken from: College Physics, Openstax, 2023.) For the quantities in Eq. (1), the length L of the conducting wire can be measured directly. Assuming the cross-section of the wire is a circle with diameter d (or radius r), the cross-sectional area A is A = mr2 = = ) The resistance R can be found by the potential difference across the wire Al and current through the wire I (Ohm's Law): R = - AV In the prelab, we ask you to derive an equation to calculate the resistivity p from quantities L, d, and R. 1118 Resistivity - 1 Saved: 4/28/23, printed: 4/28/23 Apparatus Draw a circuit diagram. List all other apparatus: Nichrome wire of two different diameters, wire leads, battery, voltmeter, ammeter, micrometer and metre stick etc. List any identifying numbers. Battery Ammeter L Nichrome wire AV Voltmeter Figure 2: Measure the length and the resistance of a nichrome wire. Data You must set up two data tables: one for the diameter d measurement, and one for the others (length L, potential difference AV and current D). Each table should have two columns for the two wires. Measure and record the diameter of one of the nichrome wires with the micrometer. Please watch the video on Brightspace to see how to use the micrometer. Be sure to make at least 3 readings and take the average. The micrometers we use usually have a negative zero reading, so your data must show the zero reading and the corrected average diameter, which is "average diameter - the zero-reading". Include the uncertainty, as usual. Set up the circuit shown in Figure 2. Measure and record the length L. Note that L is the length between the two alligator clips and is not the total length of the wire, but it should be close. Once L is measured, you cannot change the position of the alligator clips anymore. Next, measure the potential difference AV across the wire and, separately, the current / through the wire. Note that the circuit has to be broken somewhere in order to insert the ammeter to measure the current. Repeat for the other wire. Clearly state which data belongs to which wire. Calculations Calculate the resistances R of the two lengths of wire used. Use the quantities L, d, R and the equation you derived earlier, to calculate the resistivity of each wire. The resistivities of the two wires should be approximately the same. If not, your most probable error is a mistake in measuring the diameter, most likely in reading or handling of the zero reading of the micrometer. 1118 Resistivity - 2 Saved: 4/28/23, printed: 4/28/23