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# Investigation Into The Factors Which Alter The Resistance Of A Wire.

Extracts from this document...

Introduction

Investigation Into The Factors Which Alter The Resistance Of A Wire

## Aim

The aim of the investigation is to find which factors alter the resistance of a wire. This means I must find out which factors alter the resistance and I can do this by firstly selecting which factors I think will affect the resistance.

### What I am going to investigate and why

I have decided to investigate: -

1. The thickness of the wire that is to be used because there is a sufficient range of wires that I have available to me that can be tested.
2. The length of the wire that will be used, as there is also a sufficient amount of wire for many lengths to be tested which would provide many results.

In this experiment I am not going to be testing temperature and its effect on the resistance of a wire as I feel it would be rather difficult to measure and maybe harder to compare results with other factors. Also I am not going to test the effect of the material i.e. changing the wire to copper from nichrome ass there is an insufficient range of materials available. This means that I would have fewer results to base my conclusion on and therefore my conclusions maybe unreliable.

Range Of Measurements

All readings of measurements will be repeated to ensure that I acquire accurate results.

Changing the width, keeping length the same

There will be a fixed length at 15cm. The thicknesses of wire that I will investigate are: -

• 16 swg
• 18 swg
• 24 swg                                        NB: - swg = Standard Wire Gage
• 26 swg
• 32 swg

I am going to investigate these particular thicknesses of wire as they provide a suitable range and are the only ones available to me.

Changing the length, keeping width the same

There will be a fixed width at 32 swg.

Middle

Method
Experiment One - First a length of wire over a metre long is sellotaped to a metre rule. The positive crocodile clip is attached at 0cm. And the negative is moved up and down the wire, stopping at15, 20, 25, 30, 35, and 40. Each time reading the ammeter and voltmeter to work out resistance R = V/I. This is using 32 SWG wire. Other variables, voltage, thickness, and temperature will be kept constant, although the temperature will rise once current is passing through it, which will cause the atoms in the wire to vibrate, and so obstruct the flow of electrons, so the resistance will increase, creating an error.

Experiment Two - The circuit is set up is the same, as is the method apart from the length is constant at 15cm, and the thickness is changed between 16,18, 24, 26, and 32swg. For both experiments the voltage will be kept the same at 2V dc from a power pack. Both experiments will be done twice with different ammeters in case of any damaged or old equipment to gain more accurate results.

Using the micrometer I will measure the thickness of the wires. I will use skill and precision we shall measure the width of the wires in millimetres. I will then compare these widths to the widths, which are shown in the schools catalogue. We shall use a vernier calliper (or micrometer).

## Changing width, keeping length the same

Length fixed at 15 cm.

 Width (swg) Voltage (V) Current (A) Resistance (Ω) 32 1.34 0.44 3.05 26 1.04 0.99 1.05 24 0.91 1.17 0.78 18 0.37 2.20 0.17 16 0.24 2.54 0.09

We repeated the experiment

 Width (swg) Voltage (V) Current (A) Resistance (Ω) 32 1.47 0.44 3.34 26 1.01 1.10 0.92 24 0.96 1.24 0.77 18 0.36 2.22 0.16 16 0.26 2.56 0.10

## Changing length, keeping width the same

Width fixed at 32 swg.

 Length (cm) Voltage (V) Current (A) Resistance (Ω) 15 1.45 0.47 3.09 20 1.52 0.35 4.34 25 1.54 0.30 5.13 30 1.60 0.26 6.15 35 1.62 0.23 7.04 40 1.66 0.20 8.30

We repeated this experiment.

 Length (cm) Voltage (V) Current (A) Resistance (Ω) 15 1.45 0.47 3.09 20 1.53 0.36 4.25 25 1.58 0.33 4.64 30 1.65 0.27 6.11 35 1.66 0.24 6.92 40 1.70 0.21 8.10

Conclusion

These problems could be overcome by using a meter ruler to three decimal places to make the results more accurate. The wire needs to be nice and taught to measure the length. Also use a voltmeter and ammeter that are accurate and do not flicker. Therefore this would stop any anomalous results and I could have more reliable and accurate results to draw conclusions from.

The conclusions I have made are true for the length and widths of wires that I tested. There is sufficient evidence to support a firm conclusion but further experiments would need to be carried out to prove that my conclusions were true. I cannot say for sure that resistance increase with the length for all lengths of wire and I cannot say that resistance decreases with he width for all widths of wire. Different widths and lengths would have to be tested to see if this is true. I have only tested widths from 16 swg to 32 swg and lengths from 15cm to 40cm. I cannot say for sure what would happen for other lengths and widths. Other materials could be tested too to see if this alters the resistance. Other factors could also be tested such as the different voltage and material etc. Different materials such as gold, steel, silver and copper could be tested to see their effect on the resistance.

I would also use accurate measuring equipment so that no errors occur and good, clear accurate results are obtained. The good results would present a clear idea of which factors alter the resistance of a wire. Further experiments could be carried out, using different equipment to see if my conclusions are true that length and width alter the resistance of a wire

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