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Resistance of a Wire

Extracts from this document...

Introduction

Resistance of a Wire

Plan

Aim

To find out how length affects the resistance of a wire.

Introduction

In this investigation I will be looking at the effect length has to resistance in a wire. The wire I will be using is Nichrome Wire an I will be discussing on what resistance is, what affects resistance an how it can be controlled

Background Information

All things are made up of atoms and are made up of three ions, protons electrons and neutrons. Protons are positively charged, and are found in the nucleus of an atom along with neutrons that have no charge. Electrons are found in rings surrounding the nucleus of an atom.image00.pngimage01.png

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The electrons on the outer most rings in the atoms can sometimes become loose in some materials, eventually splitting into single free electrons. These electrons can move around freely, passing into the next atom and moving in random directions.

        Voltage is the measure of the electrical status or potential between two points. Voltage causes all these free electrons that are moving around in random directions to form a line and flow in one direction. Voltage can be measured by a voltmeter and in the unit of volts (V)

When the flow of electrons is formed, it can pass through materials that will allow it to. When the flow of electrons passes through a material, it is referred to as current. There are two types of current, direct and alternating. Direct current is when the charges in the flow of electrons can only move in one direction whereas in alternating current, the charges can move in more than one direction. Current can also be measured by an ammeter and in the units of amps (I).

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                                                                                                     = Direction of chargesimage09.pngimage10.png

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Middle

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Cross sectional area

The cross sectional area is the thickness of the wire. The thickness of a wire can also determine how much space there is between the atoms. In a wire with a large cross sectional are the atoms have a substantial amount of space between each other and the electrons can pass through them very easily and decreasing the number of potential collision and lowering the rate of resistance in the wire. If the wire were to be having a small cross sectional area and be very narrow, the atoms would be very close together and not allow the electrons to pass through them easily and increase the number of possible collisions and hence increasing the rate of resistance.

Type

In different wire, the sizes of the atoms vary. Some wires have very little atoms that allow the electrons to pass between them without difficulty and therefore the wire would have a little amount of resistance but in other wires the atoms may be exceptionally large and not let the flow of electrons pass through them easily without causing many collision and increasing the amount of resistance in the wire.

In the investigation I am going to do, I will be investigating how length effects the resistance and therefore will be changing the length, while keeping all the other variables constant.

Prediction

Before I started this investigation I created a prediction of what I assumed would happened that was based on my scientific knowledge. I predicted that as the length of the Nichrome wire increased, so would the resistance of the wire. This prediction was based on the grounds that I already know that when the length of the wire increases so does the number of atoms within that wire.

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Conclusion

Percentage=Difference/Predicted Results*100

Length (Cm)

Resistance

 (Ω)

Predicted Results

(Ω)

Difference

Difference

(Ω)

Percentage Difference (%)

10cm

0.8

0.8

0

0

20cm

1.6

1.6

0

0

40cm

3.1

3.2

0.1

3

80cm

6.3

6.4

0.1

2

Length

(Cm)

Resistance

 (Ω)

Predicted Results

(Ω)

Difference

(Ω)

Percentage Difference

(%)

10cm

0.8

0.8

0

0

20cm

1.5

1.6

0.1

6

40cm

3.1

3.2

0.1

3

80cm

6.4

6.4

0

0

The percentages were rounded up to the nearest whole percent. As you can clearly see the differences are very minimal and are all under 10%. The smaller the percentage difference, the more reliable they are.

Conclusion

In conclusion to having completed the whole investigation, I conclude that the predictions I made at the start were correct. The resistance did increase as the length increased. This was due to the increase in probable collisions between the metallic atoms and the free electrons that are passing through the wire. The resistance and length did have a directly proportional relationship. As said in the reason for this prediction, if the length of the wire were to double, so would the number of possible interactions, which would double the resistance. This would be the same if the length were to triple or quadruple.

I feel that the investigation was a success in most ways but it did have minute faults that could have been avoided with more equipment. Such anomalous results could have been prevented and if I had to do the same experiment and investigation again, there are some things that I would take into consideration that I may have paid little attention to the first time. The preliminary test was to familiarise myself with the circuit and procedure but not all the sources of error in the circuit had arisen in the preliminary experiment. This is the reason they were not prevented after the when the actual experiment was to be done.

        On an overall feeling about the experiment, I feel that it was an accomplishment in research over resistance and the results derived from the test were reliable and can be used in evidence when proving that length does affect resistance in Nichrome wire.

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