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# Investigating Factors That Affect The Current In A Wire.

Extracts from this document...

Introduction

Physics Coursework                Iain Rauch 10.60

## Introduction

The aim of this experiment is to see how current varies in a wire. There are five things I can vary: Temperature

##### Diameter

Length

Material

Voltage

I have chosen to investigate length. This is because temperature is too difficult to control, diameter is too small to measure, there are too few materials available and voltage will give limited results. Length is easy to measure and has a lot of varieties.

Current is electrons moving through a wire. Electrons have a negative charge. It is the rate of flow of charge.

## Aim

To see how current varies when we change the length of wire.

Preliminary Investigation

Aim

To chose a suitable voltage for the investigation. The voltage needs to provide a good range in numbers of results, without overheating the wire.

Method

For this experiment I will need to test many different wires. I will set up the apparatus shown in the diagram and take the reading of voltage and current when the wire starts to overheat. The length of the wire will be 90cm. To change the voltage, I will use the variable resistor.

Middle

Nicrome 0.45

90

0.14

Nicrome 0.45

10

1.19

Constantan 0.23

90

0.10

Constantan 0.23

10

0.83

Constantan 0.45

90

0.35

Constantan 0.45

10

2.98

Conclusion

As you can see from my results, I did not use copper in this experiment. This is because even below 1 volt, it heated up. Therefore I can not choose this as my main investigation wire. I have decided to use Nicrome 0.31. This is because there is a large range of results, but the wire did not heat up at short or long lengths. This makes the investigation safer. If we had chosen for example copper, there would be a great hazard due to the hot wire. This would also have been true of Constantan 0.45.

Main Investigation

Aim

To find out how current changes when the length of the wire is changed.

Method

For this experiment I will need to test many different lengths. I will set up the apparatus shown in the diagram and take the reading of current when the voltage is 1.0. The wire will be set at 10cm and then increased by 10cm for each reading. Every time I vary the length I will adjust the variable resistor to make the voltage exactly 1.0. For fair testing, I will try each length (10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm & 100cm)

Conclusion

Evaluation

At 40cm and 50cm the current was recorded to be too high. The points on the current graph lay slightly above the best-fit line. This could be because the equipment I used may have been as accurate and reliable as I might have hoped for.

There are several improvements I could have made to this investigation. Firstly I could have used fresh wire. The wire I used had been used before and had many notches in it. This would change the length of wire I would have been measuring. The wire was also burned in places, perhaps causing a less secure connection between the wire and the crocodile clips. Also to improve the investigation I should use more accurate voltmeters, ammeters and variable resisters.

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