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Resistance in a Constantan Wire

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Introduction

Physics Coursework Investigation.

Introduction

Aim:

Is to find out what factors affect the resistance of a constantan wire.

        For this coursework investigation I have decided to experiment the relationship of the area of wire to the resistance. I will do this experiment using several pieces of equipment and get several results organised in three tables with one table with the averages. All these tables will be put in to graphs.

        Knowledge that I already have is Ohms law and how to measure resistance using a voltmeter and an ammeter. Ohm's law states that the amount of current flowing in a circuit made up of pure resistances is directly proportional to the electromotive force impressed on the circuit and inversely proportional to the total resistance of the circuit. The law is usually expressed by the formula I = E/R, where I is the current in amperes, E is the electromotive force in volts, and R is the resistance in ohms. This enables us to work out the resistance using the current and Voltage. R=V/I.

The other piece of background knowledge is to measure resistance in a circuit using a voltmeter and ammeter. This is done by: V/I=Resistance. I know that the size of the electric current flowing through a conductor all depends on the voltage across it and the resistance of the conductor (constantan wire). When the voltage is increased the electric current increases.

...read more.

Middle

Current I/A

Resistance R/Ω

10 cm

0.75v

0.60A

1.25Ω

20 cm

0.8v

1.06A

0.75Ω

30 cm

0.7v

0.89A

0.78Ω

40 cm

0.7v

1.20A

0.58Ω

50 cm

0.5v

1.64A

0.30Ω

60 cm

0.4v

1.50A

0.26Ω

70 cm

0.3v

1.58A

0.18Ω

80 cm

0.25v

1.41A

0.17Ω

90 cm

0.25v

1.75A

0.14Ω

100 cm

0.4v

1.60A

0.25Ω

Table 2

Length in cm

 Voltage v/v

Current I/A

Resistance R/Ω

10 cm

0.7v

0.28A

2.5Ω

20 cm

0.3v

0.55A

0.54Ω

30 cm

0.3v

0.64A

0.46Ω

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Conclusion

 In my opinion the average table show the best set of results. The line of best fit on the graph is clearer and smoother than the other two sets of results. There are no ups and downs in this set of results. This is also makes it clearer and easier to understand.

Evaluation:

I am pleased with my results and graph but if I were to do the experiment again I would change several things. The first thing that I would change would be the equipment. I would do this by making sure that each piece of equipment was new and all in working order to make sure that I could get the best results possible. The second thing that I would do is to stick to a strict limit, so that the wire and apparatus would not get to hot, this may effect the readings. Thirdly if I was to the investigation again I would, choose another variable instead of thickness. Instead I would choose the length. To do the length experiment I would need the same apparatus that I have used for the thickness experiment. The only thing that will be different is that I will be taking a reading every 5 centimetres giving me a more accurate set of results and also giving me a better plotted set of results on the graph. The wire that I will be using should still be 100cm.

Conclusion:

...read more.

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