Measuring the Resistivity of a Wire

Authors Avatar

        

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.

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:

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=ρl    or    ρ = RA             (where A = Area of cross section, R = Resistance, l =

    A                         l                      length, and ρ = 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.
  • Voltmeter – To measure the p.d. in the circuit to then find out the resistance. This is accurate to 0.01V.
  • Ammeter - To measure the current in the circuit to then find out the resistance. This is accurate to 0.01A.
  • Nichrome wire – This is the material that I will be testing on in wire form; ultimately I am trying to find its resistivity.
  • Ruler – To measure the length of the wire that I am testing. This is accurate to 1mm.
  • Micrometer – to measure the diameter of the wire and then be able to find the area of the cross-section. This is accurate to 0.01mm.
  • Variable resistor – to give me more results for each to give me an idea of accuracy.
  • Switch – so that the power is not constantly running through the circuit thus causing the wire to heat up.
Join now!

During this experiment I need to be aware of the safety element of it and therefore prevent any possible hazards before they can occur. As there is electricity involved I will ensure that the experiment is set up away from any water or other aquatic conductors. I will make sure that the power supply does not exceed 3V so as not to have a dangerous current flowing through it. I will also wear safety goggles to protect my eyes as there is a possibility of the wires snapping. There is also a chance of the wire becoming very hot ...

This is a preview of the whole essay