Measuring the Resistivity of a Wire

Measuring the Resistivity of a Wire

Aim

The aim of this experiment is to find out how the area of the cross

section of the wire affects the resistance and also to find out the

resistivity of the wire having found the resistance over a certain

length and using a certain cross sectional area. I will also

experiment to see how the length of the wire affects the resistance.

Plan

The first thing that I will do is to set up the apparatus as shown

below.

A,V

Except for the experiment where I alter the length, I will keep the

length of the wire constant throughout the experiments and only change

the diameter of the wire. For each width I will record the p.d. and

current displayed on the voltmeter and ammeter. I will then use these

values to calculate the resistance of the wire at that length using

the formula:

[IMAGE]V = IR or R = V (where V = p.d., I = Current, and R =

Resistance)

I

I will then find the cross sectional area of the wire. To do this I

will find the diameter of the wire using a micrometer. Then I will

find the area of the cross section by using the formula:

Area = πr² (where A = Area of cross section, π = pi, and r = radius)

Once I have this value I will be able to calculate the resistivity of

the wire by substituting the values into this formula:

R=rl or r= RA (where A = Area of cross section, R = Resistance, l =

[IMAGE][IMAGE] A l length, and r= resistivity)

I will repeat this for all of the different diameters that I will test

but will remember to keep the length of the wire the same throughout.

The apparatus that I will use for this experiment are listed below:

· Power supply - This will be 3V of power and will be used to power

the circuit so that I can measure the resistance of the wire.