Investigation of The Resistance of Wires

Investigation of The Resistance of Wires

The Experiment

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The experiment that was used to obtain the results was very simple.

The voltage and current were measured whilst varying the length of

wire. The results for voltage and current were recorded along with the

diameter of the wire. This allowed for a range of other values to be

calculated, including cross-sectional area and resistivity.

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The Equipment

* A power supply

* A voltmeter and an Ammeter

* A jockey

* A micrometer

* A 1 meter ruler

* Wire

* Connecting cables

What is Resistivity?

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The resistance of a conductor depends on three factors:

1. The material

2. The size of material (eg length)

3. The temperature

The equation for Resistance is:

R = rl

A

In this equation the constant is called resistivity, r. This is

governed by the nature of the material and is affected by temperature.

Resistivity varies for different materials, but stays constant for a

given material. Below is a table illustrating a few materials

resistivity

The equation for resistivity therefore is:

r = RA

L

The units for resistivity are Wm (ohm-metres).

Conductivity

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The opposite of resistivity is conductivity. This can be calculated by

using this formula:

s = 1/r

The units are W-1m-1.

Predictions

I think that the results that I work out will show these patterns:

* As the length increases the resistance will also increase - there

is more wire resulting in more energy needed for the same results

* As the Cross-Sectional Area increases the resistance will decrease

- the wire is 'wider' resulting in more electrons being able to

flow at any one time