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Investigate how the length of a wire affects resistance.

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Aim: Investigate how the length of a wire affects resistance.


My prediction is when the length of a wire increases its resistance increases as well. This prediction is a result of a simple theory. We know that everything is made of atoms. Atoms are made up of neutrons (neutral), protons (positive) and electrons (negative). Atoms have positively charged nucleus which contain the neutrons and the protons. They are surrounded by negatively charged, electrons. In metals the electrons are weakly attracted to the nucleus so they escape and are free to roam between atoms. When the metal is connected with any source of power, these electrons slowly flow in one direction. This slow flow is called the current. As the electrons flow through the metal they collide with the atoms and transfer energy to them. The electrons experience resistance to their forced movement between the atoms. When the electrons collide with the atoms the electrons lose energy and slow down. So, when the length of the wire increases the number of atoms and electrons increase. We also know that it

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Then work out the resistance using the formula: Voltage ÷ Current = Resistance
  1. We were told to turn the voltage to 3V so that overheating was minimized and also lengths lower than 10cm were not tried, which also helped to avoid overheating.

Factors Affecting the Results


Why/How do they affect?



When there is a current flow the atoms seem to gain energy due to collisions with the electrons. They also vibrate faster which means temperature is high and resistance increases due to high temperatures.

To control this we need to switch off the PSU after taking the readings of each result and turn on only when taking next result.

Material of the wire.

If the material is a good conductor of heat then resistance increases again.

 Use a constatan wire.

Error of equipment

Readings might be taken incorrectly due to intrinsic equipment.

There is no solution.

Voltage of the PSU

Even though the PSU is set at 4V, the voltage given might be between 3.5V and 4.5V.

We have to measure the voltage for each set of results using a voltmeter.

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Most of my results were reliable. Look back at the page Observation’. The results marked in green are very reliable except for the one result marked in blue which is not very reliable. I think it one of the anomalous and caused mostly due to overheating of the wire. The only thing to be done is to remember to switch off the PSU after taking result. Also repeat readings for unreliable results to see improvements can be made. I think the rest of the results are accurate or reasonably accurate.

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This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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