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What affects the resistance of a wire

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Elena UtevaWhat affects the resistance of a wire?


In the following investigation I shall explore and come to a conclusion on the variables that affect the resistance of a wire.

Resistance is defined as the property of materials which oppose the flow of electric current to some greater or lesser degree. It is caused by the free electrons colliding with the ions in the material and the energy provided by the applied voltage being converted into heat, which consequently decreases the electron’s speed and increases the resistance.

The resistance of a conductor is the ratio of the potential difference applied across it, to the current passing though it. The SI unit of electrical resistance is the ohm (Ω) and a resistor has the resistance of one ohm when a potential difference of one volt will maintain a current of one ampere.

Ohm’s law is founded by George Ohm and states that the current passing through a circuit is directly proportional to the applied voltage and inversely proportional to the resistance of the circuit providing the temperature remains constant. (http://micro.magnet.fsu.edu/ electroma /java/ohmslaw/).

The relationship between voltage and current is expressed by the following equation:

I =

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After performing the preliminary experiments and studying the results, it was decided that 4V will be used in our actual experiment and that we will have a difference of 5cm between each length.

After setting up my experiment, I shall then turn on the power supply for the low voltage unit and switch on the ammeter and voltmeter. In order to maintain safety in the following experiment, a low voltage will be used so there will be minimal overheating and so the wire will not burst into flames.

After taking a reading of the voltmeter and ammeter, I shall then record the results in a table. I shall then turn off the power supply and move the crocodile clip from the 5cm to the 10cm position, repeating the procedure above. I

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To improve the overall accuracy and reliability of my experiment I would alter the method of the investigation. In order to control the temperature variable in the experiment, I would leave the wire to cool completely during measurements or would use several wires of the same material and width. To improve the accuracy of the measurement of the wire I would use clips smaller than a crocodile clip so therefore the length of the wire would be as accurate as possible. As well as that, since the voltmeter and ammeter only gave the readings to 2 decimal places, improve my accuracy I would use equipment that is more accurate and that gives the readings to more decimal places, such as a to computer.

In conclusion, the investigation has shown me that by increasing the length of the wire, the resistance also increases in direct proportion. To further extend my investigation, I could test another variable and investigate its affects on the resistance of a wire. For example, I could test the affect of the temperature or the cross-section area on the resistance of the wire and could find the formula that expresses their relationship.

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