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To find out what happens to the resistance of a wire, when you change the length of the wire.

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Introduction

Resistance Of Wire. Aim. To find out what happens to the resistance of a wire, when you change the length of the wire. Background Information. A current of electricity is the flow of negatively charged electrons around a circuit. [image001.gif] [image002.gif] [image002.gif] [image003.gif] [image003.gif] [image004.gif] [image005.gif] Close up, the wire and the electrons look like this: [image006.gif] The electrons collide with the atoms as they travel through. We say the atoms `oppose' the flow of electrons. This is called resistance, and the wire gets hotter. In 1826, Georg Ohm discovered that when a current flows through a metal wire the current and the potential differences are proportional, providing that the temperature remains constant. The resistance of wire can be calculated using: [image007.gif] Variables. Temperature increases the resistance as the atoms are getting hotter they are vibrating and moving faster. This makes the atoms and the electrons collide more. Thickness of wire decreases the resistance, as there is more room for the electrons to travel past the atoms. ...read more.

Middle

and attach them to a power pack, a voltmeter and an ammeter using crocodile clips. I will use one length of wire at a time. When I turn the power on, I will record the current and voltage quickly to 2d.p for accuracy. [image008.gif] Then I will work out the resistance using Ohms Law: [image009.gif] I will do this for all five measurements. I am using these measurements because my preliminary work gave me a good result when I tested them. I will repeat the tests three times to make sure that I get an reliable result. This way my results will be reliable. Results. Length of wire. Current (Amps) Voltage (Voltage) Resistance (Ohms) Average (Ohms) 10cm 0.17 0.01 17 17.5 10cm 0.18 0.01 18 10cm 0.19 0.08 2.374 20cm 0.22 0.01 22 21 20cm 0.21 0.08 2.625 20cm 0.20 0.01 20 30cm 0.01 0.20 20 21 30cm 0.03 0.21 7 30cm 0.01 0.22 22 40cm 0.01 0.18 18 20 40cm 0.01 0.22 22 40cm 0.01 0.21 2.625 50cm 0.01 0.22 22 21.5 50cm 0.01 0.21 21 50cm 0.04 0.20 5 Analysis. ...read more.

Conclusion

I could change this by increasing the length of the wire or keep lengths the same as before but use a different type of wire. My graph shows this. I have realised that the readings must have been wrong, but I would retest them. To make my results more accurate, I would repeat the experiment. I have enough evidence to reach a conclusion. My results match what other people have found. To additional evidence, I would do another experiment using the same measurements but different types of wire e.g. constaintin. I would do this because I could see if the two odd results became more accurate and because it is known to have a higher resistance than copper wire. To extend my investigation I could use lengths of wire over 50cm. Or, to test my work, I would use a different type of wire. This would change my results because every different types of wire have their own arrangement of atoms (obstacle course). ...read more.

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