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# Investigate the factors that affect for the resistance of a wire.

Extracts from this document...

Introduction

Nirali Patel        Physics coursework        John Larwood

As part of my physics coursework, I will investigate the factors that affect for the resistance of a wire. E.g. length and diameter.

PLANNING

Hypothesis:

I am investigating the factors that affect a wire. I predict that the following have an affect on the resistance of the wire:

1. The material of the wire (what is the wire made out of)
2. The length of a wire.
3. The cross sectional area of a wire
4. the thickness of a wire

Resistance

The current flowing through a metal wire is proportional to the potential distance across it (providing that the temperature remains constant.)’ (physics for you by Keith Johnson) we say that a wire has a certain resistance to the current. The greater the resistance, the greater the voltage is required to push a current through a wire. Resistance is any sort of constriction in the flow.

Resistance is better described through ohm’s law:

Resistance= potential difference across the wire

Current through the wire

R=V

I

Where R=resistance

V=volts

I=current.

Ohm’s law

Ohms Law is states that); "Provided the temperature remains constant, the ratio of potential difference (p.d.) across the ends of a conductor (R) to the current (I) flowing in that conductor will also be constant".

(From CPG Physics complete practice and revision)

In other words, the current passing through a wire at constant temperature is proportional to the potential difference between its ends.

Resistors

Middle

0.041

40

0.36

5.68

0.046

50

0.30

5.54

0.054

Copper wire 36 SWG (thin)

 Length (cm) Voltmeter (V)Volts Ammeter (A)Amps R=V/I (Resistance)Ohms 10 0.50 4.02 0.12 20 0.72 3.20 0.23 30 0.82 2.94 0.29 40 1.06 2.75 0.39 50 0.95 2.4 0.4

Nichrome wire 32 SWG (thick)

 Length (cm) Voltmeter (V)Volts Ammeter (A)Amps R=V/I (Resistance)ohms 10 1.50 0.87 1.72 20 1.63 0.45 3.62 30 1.73 0.32 5.41 40 1.79 0.25 7.16 50 1.85 0.20 9.25

Nichrome wire 36 SWG (thin)

 Length (cm) Voltmeter (V)Volts Ammeter (A)Amps R=V/I (Resistance)ohms 10 1.56 0.45 3.47 20 1.60 0.22 7.27 30 1.70 0.15 11.3 40 1.74 0.12 14.5 50 1.79 0.10 17.9

Analysis

From the results that I got I will plot various graphs that will help me come to an end to this investigation and see whether my hypothesis was correct or incorrect.

Graph 1

Graph 1 is a graph of the resistance of the copper SWG 24 wire against the length of the wire. From this graph, I can see that the resistance increases as the length increases. This means that the longer the wire gets, the more it will resist.

I did not get any anomalous results for this experiment as all the results I got fitted the line of best fit.

Graph 2

The second graph is a graph of the resistance of a copper wire of SWG 36 against the length of the wire. As I found out in graph one that as the length increases so does resistance, I got the same result in this graph but unfortunately, I got an anomalous result, the reading for the 50cm wire does not fit into the line of best fit. There are many reasons why this has happened and some of the reasons are:

1. the wire was not in full contact with the crocodile clips

Conclusion

1. the crocodile clips were not clipped properly
2. The wire may have coiled up and jumped to make it unfair.
3. The wire may have been rusted or corroded which helped prevent the flow of electrons consistently, which affected the result of the experiment.
4. The correct size of wire may not have been used.

Improvement methods

If I would be able to conduct this experiment a second time I would do the following things:

1. conduct a preliminary experiment first so that there is a rough idea of what the actual results should be like
2. I would repeat each wire of each thickness of each length at least 3 times and then take an average. The main reason for this is so that it is quite certain that the results obtained are correct. The experiment which I conducted above did not have more that one per wire per thickness per length.
3. I would make sure that none of the wires are corroded or rusted or bent, I will use brand new wires so that the best possible results are obtained.

Although it was not possible in this experiment for me to take more than one reading and then take out an average for it to put for my final result I should have checked my results thoroughly and repeated any experiments were the results did not seem normal.

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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