• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10

Investigating the resistivity of an unkown wire

Extracts from this document...

Introduction

Michael Ofori

image00.png

image17.png

image01.png

Introduction

The aim of this investigation that I am about to embark on is to research into the resistivity of a wire found on an ancient mummified Persian princess who according to one translation is a daughter of the King Xerxes which was about 2,600 years ago.

After I have found the resistivity of this wire, I will compare and contrast it with other resistivities of the different types of contemporary wires available today in order to interpret and conclude whether it is made from a modern alloy.

Theory

An electric current in a wire is the passage of moving charge through the material. Charge is carried by particles such as electrons and ions. In some materials such as a metal, the charge is carried by electrons. In other materials such as salt solution, the charge is carried out by ions. If charged particles are moving, a current is produced. Electrons moving in a circuit are negatively charged. They move from the negative terminal to the positive one. In spite of this, the direction of the current in a circuit is taken as being from positive to negative.

A current in a wire is due to the movement of free electrons. A wire consists of millions of atoms which have electrons tightly bounded to the atomic radius by the electrical attractive force between the positive nucleus and the negative electrons. In solids, one or two of the outer electrons surrounding each atom are used to form the bonds between atoms that hold the solid itself together.

...read more.

Middle

image02.png

image03.png

image04.pngimage05.png

image06.png

  • Firstly, measure the diameter of the wire at 6 different lengths using a micrometer and workout the mean diameter of the wire.
  • Set up experiment as shown in the diagram
  • Connect power supply to ammeter (using connecting wires) and from the ammeter to the research wire using a connecting wire clip
  • Connect the other end of the research wire to the variable resistor (again using a wire clip) and from the variable resistor to the power supply
  • Connect the voltmeter in parallel to the wire (as voltmeters have high resistance and will not let current through if connected in series).
  • Make sure the ammeter and voltmeter reading is zero before turning on power supply
  • After power supply is turned on, change the resistance of the circuit by the use of the variable resistor and take accurate measurements of the current and voltage using the ammeter and voltmeter when resistance is changed.
  • If the wire gets hot after when measurements have been taken, wait until the wire cools down before taking next measurement in order to prevent biased data.
  • Carry out 8 experiments and repeat any test if necessary.
  • When all measurements have been taken, insert them into a well structured table containing units, headings etc and draw a correlation graph to work out median resistance (R=V/I) and also observe the relationship between voltage and current.
  • Using the calculated mean diameter of wire, calculate the radius and cross-sectional area of wire using the formula πr2 and work out the resistivity of the wire using the formula (ρ = RA / L)

Safety

...read more.

Conclusion

Percentage error =  Error in reading

                                Average value

Micrometer  

% error = 0.001mm

                0.565mm

= 0.176 %.

This is percentage error is not significantly high as it is under 1% so therefore the micrometer measurements were quite accurate to my surprise. However, because they do not correspond to my expectations in determining the percentage error of my calculations which was due to the instruments that was given to me, I will also calculate the percentage error for the voltmeter and ammeter as well to see which instrument carried the most percentage error which ultimately resulted in variation of my data with published data values.

Voltmeter

% error = 0.01

                0.05

= 20 %.

The concludes that the voltmeter carries a slight degree of error associated with the voltmeter measurements I took and this ultimately causes a clear distinction between published data values and my value. In future experiments, I will use a different and a more accurate voltmeter for precise measurements.

Ammeter

image10.png

% error = 1mm

                25mm

= 4%

Although this percentage uncertainty value is also not significantly high, it also contributes to variation between data sheet values and my value. This percentage error in opinion was caused from using an analogue ammeter to measure the current. I had to manually measure the current with my eye considering the parallax error and factors of that nature although I had considered these factors earlier in my plan. Because an analogue ammeter was used, I was unable to measure the current to a satisfying degree of accuracy. In future experiments, I will improve the measurements of current using a digital ammeter.

Bibliography

  1. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html
  2. AS physics, isbn: 0435628925
  3. http://hyperphysics.phy-astr.gsu.edu/HBASE/Tables/rstiv.html

...read more.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Electricity and Magnetism essays

  1. Marked by a teacher

    Draw stress and strain graphs for the metal copper and the alloy constantan. Calculate ...

    4 star(s)

    The calculations I did for cross sectional areas of both wires is shown below: Cross sectional area = ?r� Copper "r"= 0.37/2= 0.185mm Conversion to m= 1.85E-4 Calculations= ? (0.000185�) = 1.08e-7m� Cross sectional area= ?r� Constantan "r" = 0.35/2= 0.175mm Conversion to m= 1.75E-4 Calculations= ?

  2. An experiment to find the resistivity of nichrome

    The pointers would be more accurate because the tips have a much smaller area than the crocodile clips giving a more accurate measurement of the length of wire. As well as making these modifications I would also improve my Investigation by testing the same wire but different widths of that wire.

  1. To investigate how the length (mm) and the cross-sectional (mm2) area of a wire ...

    to one decimal place instead of two, and my results would not have been accurate enough. All these factors could have affected my results so that I got a few anomalies. These anomalies were not enough to tip the balance though, and my results were very conclusive in proving my hypothesis that resistance was directly proportional to length.

  2. Resistivity.My aim is to measure the resistivity of the wire alloy Constantan

    Lengths of below 10cm will not be experimented on to prevent overheating. Intended readings, The longer the wire the larger the resistance should be. This will make the resistance smaller. Alloy Composition Resistivity Resistivity Temperature coefficient Constantan 57Cu, 43Ni 49 249 .0001 Constantan, Design Justifications, I chose to stay below

  1. Resistance and Wires

    To improve the reliability of the experiment, I could have taken more readings of the recordings of each length of wire. This would have meant that I could have calculated a more accurate mean and hade a more detailed range bar.

  2. Electromagnetism - investigating what effect increasing the number of turns in a coil on ...

    I feel that the sudden increase in strength of the electromagnet was due to temperature, the rise in temperature came from the wires getting hot, the rise will have caused this sudden surge in energy. Reliability From my results I feel that they were good enough to support a firm

  1. Find out how resistivity changes as the length of wire is changed, and to ...

    I would also need to ensure that the crocodile clips were placed in the exact positions on wire e.g. 10, 20... cm etc. this would ensure reliable and more exact results. All these will have to be taken into account and will help me to minimize errors when calculating the resistivity of my unknown piece of wire.

  2. Investigating the resistivity of constantan

    Accuracy In order to minimise errors and for a fair test, I will measure the diameter of the wire using a screw gauge at several different places and at different directions across the wire. I will then work out an average of these measurements.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work