The factors that affect the resistance of a wire

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The factors that affects the resistance of a wire        Tom Pattle

The factors that affect the resistance of a wire

By Tom Pattle


Contents

Plan - Pg 4 ~ 11

Introduction - Pg 4

Background Knowledge – Pg4  ~ 7

Prediction – Pg 8

Method – Pg 9  ~ 11

Results - Pg 12 ~ 13

Analysis – Pg 14 ~ 16

A graph to show the resistance of a wire at room temperature – Pg 16a

A graph to show the resistance in a wire when kept at a constant temperature – Pg 16b

A graph to show the resistance in a wire when at room temperature and kept at a constant temperature – Pg 16c

Evaluation – Pg 17 ~ 18

References – Pg 19


Plan


Introduction

        The experiment that will be carried out is about the factors that affect the resistance of a wire using Nichrome 32SWG. When a current of 0.10 amps is passed through this wire, a resistance will form. The voltage will be measured, and using the following equation the resistance will be calculated:

Resistance = voltage ÷ current

(this equation is explained further on page  5)

By finding the resistance when the Nichrome is at different lengths and when the temperature is kept constant will show us the factors that affect the resistance of a wire.

Background Knowledge

        For this experiment to be successful, one of the four factors that effect resistance must be included in the experiment:

        

As the length of the wire increases, the resistance increases.

But there are also different factors that effect resistance in a wire. The flow of electrons (current) that pass through a wire affects the temperature. A rise in temperature increases the vibration of atoms inside the wire and so electrons bump into the atoms more often and so the resistance increases. For this reason, the current must be kept as low as possible throughout the practical.

        The diameter of wire also affects the amount of resistance. For example, a wire which has a large diameter has more room for the electrons to flow, thus the wire having a low resistance so a higher current may flow through it. But if a wire has a small diameter, there is less space for the electrons the flow and so the wire will have a high resistance so only a small current can flow through it. On the next page is a diagram that will help to explain this further:

The diameter of a wire is not the only thing that affects the resistance travelling through it. The length of the wire is also important to keep resistance down because long wires have more resistance than short ones. Since the electrons that have to flow through the wire have a greater distance to travel if the wire is of a longer length. The diagram over the page shows how length and diameter affects the resistance in a wire:

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Resistance can also vary depending on the material the wire is made out of because the diameter of the wire could be different or there could be more or less atoms inside the wire. A wire made of Nichrome has more resistance than a copper wire of the same size. That’s why, in circuits the connecting wires are usually made of copper because it has a low resistance.

        Previously, an experiment was carried out to show the relationship between voltage and current for a bulb. It showed that the bulb was ...

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