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# Investigating the Physical Factors that affect the Resistance of a Wire.

Extracts from this document...

Introduction

## Introduction

An electric current in a wire is a flow of charge due to electrons moving along the wire. Electric current is measured in amperes (A).

The potential difference (p.d.) between two points in a circuit is the electrical energy converted into other forms of energy when one coulomb of charge passes from one point to the other. The potential difference unit is the Volt (V). It is also known as voltage.

When the same potential difference is applied across different conductors, different currents flow. Some conductors offer more opposition or resistance to the passage of current than others do.

The resistance, R, of a conductor is defined as the ratio of the potential difference (V) across it, to the current (I) flowing through it:

Resistance = Potential Difference

Current

Resistance is measured in Ohms (Ω). One Ohm is the resistance of a conductor in which the potential difference applied across it is 1 Volt, and in which 1 Ampere of current is maintained. A wire has resistance because when the current flows through the wire, the electrons move along. As they are moving, the metal atoms obstruct the flow of electrons, slowing the flow down. this is resistance.

Middle

(V)

Resistance

(Ω)

Range of resistance

(Ω)

Constantan 22swg, 10cm

0.4

0.0

0.00

0.50

Constantan 22swg, 30cm

0.4

0.2

0.50

Constantan

34swg, 10cm

0.4

0.4

1.00

2.25

Constantan

34swg, 30cm

0.4

1.3

3.25

Manganin 28swg, 10cm

0.4

0.2

0.50

0.75

Manganin

28swg, 30cm

0.4

0.5

1.25

Manganin

30swg, 10cm

0.4

0.2

0.50

0.75

Manganin

30swg, 30cm

0.4

0.5

1.25

Nichrome

22swg, 10cm

0.4

0.1

0.25

0.00

Nichrome

22swg, 30cm

0.4

0.1

0.25

Nichrome

32swg, 10cm

0.4

0.6

1.50

3.50

Nichrome

32swg, 30cm

0.4

2.0

5.00

##### Conclusion

As the results show, Nichrome 32swg had the highest range of resistance from 30cm to 10cm. For the main investigation, I will investigate how the length of a wire (Nichrome 32swg) affects its resistance. I am going to use 32swg as this has the largest resistance range. As 32swg is the narrowest wire, we can also learn that the narrower or thinner the wire, the larger the resistance.

Fair test

• The current was kept constant throughout the investigation to ensure that the results were not affected by a change in the amount of current supplied, and by the temperature of the wire.
• Two lengths of wire were used, at 10cm and 30 cm, so a range of lengths could be used to make the results more accurate.
• The temperature was kept the same, at room temperature, to ensure the final value for resistance was accurate and not affected by temperature.

Safety precautions

• The power pack will be turned on and off as quickly as possible to prevent the wire from over heating.
• The circuit will be connected up securely and will be checked before being used, as any lose flow of electrons could be dangerous.
• When cutting the wire with the wire cutters, care will be taken to prevent being cut by the wire cutters.

Conclusion

There are different ways in which the method could be improved to make the whole experiment more accurate. In this investigation, only one factor was investigated however, other factors could have been investigated. Also, different types of material could have been tested to see if the theory: Resistance  Length remains true. Also, a more accurate or sensitive voltmeter could have been used to make the voltage readings more accurate. An ohmmeter could have been used as well as the method which we used, so that the two sets of readings could be compared. From this we could have seen how accurate the sets of results were. The resistance of the wire could have also been measured using the equation:

Resistance =    L

###### A

The results for that could have also been compared with the results obtained from the original investigation.

Overall, I think that the investigation was carried out fairly and accurately and this can be seen by the results, which support the prediction and the theory that length is proportional to resistance.

BIBLIOGRAPHY

www.ai.it.edu

Microsoft Encarta 96 Encyclopaedia

GCSE Science Assessment Sc4

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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