Investigating how the length of wire affects its resistance

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Investigating how the length of a wire affects its resistance

Aim:

To find out how changing the length of a wire will affect its resistance.

Introduction

Electricity is conducted through a conductor by means of free electrons. An electric current is made up of charged particles that flow called electrons. They move through a conductor, e.g. wire. The more free electrons in a conductor there is, the better it will conduct electricity as more mobile electrons mean more flow. Conductors of different materials have different amount of free electrons, therefore, some conductors conduct electricity better than others.

Resistance is what opposes the flow of current, (obstruction offered by the wire) and is measured in ohms, with the Greek symbol: Ω. Resistance makes it difficult for the flow of electrons through the conductor. It can be caused electrons colliding with atoms in a conductor, obstructing the flow. Electrons will also collide with each other if there is little free space in a conductor, and so resistance will increase.

Resistance can be affected by several different factors, such as light, temperature, width of wire, cross section area of wire, as well as the length of wire. In this experiment, I am going to investigate how the length of a wire will change its resistance. I will be using a range of wire lengths to test this.

 

Formula:

Resistance= Voltage/Current         R= V/I  

From the equation, I can obtain the resistance by measuring the voltage and current. I will use the reading for the current from the ammeter divided by the reading for the voltage from the voltmeter to calculate the resistance.  I can then know how I will be collecting my results.

 

Prediction:

I predict that the longer the length of wire is, the higher the resistance. This is because if the wire is longer, there would be more atoms along the way, thus increasing the chance of the flow of electrons and atoms colliding, creating the flow of electrons to be more difficult as there is less free space for electrical charge to flow through. Because the wire is longer, the chances of the electrons colliding with each other also increases, so this causes obstruction and resistance will increase.

In this case, there will be different lengths of the wire measured, and the longest wire will have the highest resistance. (With the width kept the same). With more atoms, the more likely the moving electrons will collide with them, and so the flow would be less meaning a higher resistance.  With more length, the chances of the neighbouring electrons colliding with each other should also increase.

Quantitative prediction:

I predict that the results will show that doubling the length of the wire (without changing anything else) will double the resistance, as the twice the length of wire is, there would be twice as many atoms meaning the chance of the moving electrons colliding with the atoms would be twice as much. Resistance should also double if length doubles because it means there is twice as much chance for the neighbouring electrons to collide with each other.

For example, if the length of my wire was 25cm, then the number of atoms will double if the length of my wire was 50cm, as the mobile electrons will have to travel double the distance. (Say a 10cm wire would have 5 atoms, a 20cm wire would have 10 atoms. So if 5 electrons try pass through the second wire, the chances that they will bump into the atoms as well as each other is double.) Therefore, I predict that doubling the length of a wire means that the resistance will double.

Plan

Preliminary Experiment

1.5 V  (every 5 cm up to 50cm)

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For my preliminary experiment, I was experimenting on how I should set up for my real investigation. I adjusted different volts on the power pack. I initially used 1.5V, which gave me the results in the first table. It showed a clear trend, and there was no overflow of current, as my ammeter had no trouble displaying any readings. There was no problem with the readings on the voltmeter either, which stayed the same throughout. (Because of the low readings I only had to connect the wire to the 3V on the voltmeter)

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Overall, this is a good report because it is very thorough in trying to analyse the results. Good comments have been made about controlling aspects of the experiment and no attempt has been made to ignore an anomalous result. The addition of a graph would have improved this report. 3 stars