Finding the resistivity of a wire (4.1)

Question 1

What equipment do you need to find the resistivity of a wire?

Answer 1

Power supply, ammeter, voltmeter, ruler, flying lead

Question 2

How can you increase accuracy of results in the resistivity experiment?

Answer 2

Only have small currents flowing through the wire, and for short periods of time. This is because current makes the wire heat up, increasing it’s resistance. So the wire must stay at a constant temperature for the results to be valid.

Question 3

How do you obtain results for finding the resistivity of a wire?

Answer 3

1) Use a micrometer to measure the diameter of the wire in 5 different places and get an average. Calculate the average cross sectional area using A = πr^2
2) Clamp the test wire to a ruler and connect to the rest of the circuit at the point where the ruler reads 0
3) Attach a flying lead to the test wire at 0.1m
4) Record the length of the connected test wire and the resistance of that length using R = V/I
5) Repeat step 4 moving the flying lead up in 0.1m intervals up to 1m

Question 4

How do you calculate resistivity from the results obtained in the experiment?

Answer 4

Plot a scatter graph of resistance against length and draw a line of best fit. The gradient of this line of best fit is equal to R/L = p/A
So multiply the gradient by the average cross sectional area of the wire to get it’s resistivity