The resistivity (ρ) 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 = ρ.l / A,
where A is the cross-sectional area of the wire (A = πr²).
The resistivity can be calculated from the formula: ρ = R.A / l.

- Drag the slider to move the contact along the wire. At some point, record the resistance and the length of the wire.
- Press "Get Micrometer". In this simulation a full turn of the circular scale reads from 0 to 50 and represents 0.5 mm. Note: initial reading = 3.72 mm, distance scaled up a little to make it more readable.
- Press "Check Zero Error". A reading between 0.00 and 0.03 will show and therefore will have to be subtracted from later readings.
- Press "Measure Diameter". Record the value and repeat until you have at least six readings. Calculate the average diameter.
- Calculate the resistivity of the material of the wire.
- Move the slider and therefore the sliding contact to a new position on the wire and again record length and resistance and again calculate resistivity.

**Precautions:**

- Ensure that the wire is straight when measuring its length. Measure only between the ohmmeter contacts.
- Take great care with the micrometer screw guage and the zero error, if present. Take the average of at least six readings as a very small error in the diameter of the wire causes a large error in the resistivity calculated.
- To avoid errors in the resistance readings press the ohmmeter contacts together and zero the ohmmeter, or else subtract the resistance of contacts and connections from later readings.