# Measuring the Resistivity of a Wire

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Introduction

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)

Middle

0.00

0.00

SWG | Diameter (m) | Length (m) | Area (m²) | Current (A) | Voltage (V) |

38 | 1.95E-04 | 0.5 | 2.98E-8 | 0.07 | 2.33 |

38 | 1.96E-04 | 0.5 | 2.98E-8 | 0.07 | 2.27 |

38 | 1.95E-04 | 0.5 | 2.98E-8 | 0.08 | 2.38 |

38 | 1.95E-04 | 0.5 | 2.98E-8 | 0.09 | 2.85 |

SWG | Diameter (m) | Length (m) | Area (m²) | Current (A) | Voltage (V) |

26 | 4.4E-04 | 0.5 | 1.52E-07 | 0.23 | 0.84 |

26 | 4.4E-04 | 0.5 | 1.52E-07 | 0.25 | 0.89 |

26 | 4.4E-04 | 0.5 | 1.52E-07 | 0.27 | 0.97 |

26 | 4.4E-04 | 0.5 | 1.52E-07 | 0.32 | 1.13 |

26 | 4.4E-04 | 0.5 | 1.52E-07 | 0.36 | 1.30 |

26 | 4.4E-04 | 0.5 | 1.52E-07 | 0.44 | 1.56 |

26 | 4.4E-04 | 0.5 | 1.52E-07 | 0.58 | 2.08 |

26 | 4.4E-04 | 0.5 | 1.52E-07 | 0.67 | 2.41 |

SWG | Diameter (m) | Length (m) | Area (m²) | Current (A) | Voltage (V) |

18 | 1.19E-03 | 0.5 | 1.11E-06 | 0.31 | 0.16 |

18 | 1.19E-03 | 0.5 | 1.11E-06 | 0.35 | 0.18 |

18 | 1.19E-03 | 0.5 | 1.11E-06 | 0.46 | 0.23 |

18 | 1.19E-03 | 0.5 | 1.11E-06 | 0.56 | 0.29 |

18 | 1.19E-03 | 0.5 | 1.11E-06 | 0.69 | 0.35 |

18 | 1.19E-03 | 0.5 | 1.11E-06 | 1.01 | 0.52 |

18 | 1.19E-03 | 0.5 | 1.11E-06 | 1.82 | 0.93 |

18 | 1.19E-03 | 0.5 | 1. |

Conclusion

Another factor that could have affected my results could have been faulty equipment such as the voltmeter and ammeter may have not been very accurate or could have been telling me different values altogether although I am confident that this was the case due to the shape of my graphs drawn. This is due to my scientific knowledge that the Voltage and current are proportional to each other as shown in my graphs.

If I was to repeat this experiment I would do use the same method as I did in this one as I believe it to be the most effective way in determining the resistivity of a wire with the equipment available for me to use.

Richard Hawson 12La Resistivity Coursework

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

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