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The Resistance of a wire

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The Resistance of a wire

The investigation is about resistance. In this investigation a simple circuit will be set up to read the voltage and current when the length of wire changes.

For the investigation I will need the following equipment:

*Variable power source



*Crocodile clips

*Electrical wires


*Nichrome wire- (resistor)

The apparatus should be set up as followed:


“Resistance is the measure of how hard it is to get a current flowing through a component at a particular voltage.”-Ionsdale science revision guide

Resistance =  Voltage (V)

     (   )            Current (A)  

“This is known as the ohms law. It is only true if the temperature of the wire is at a constant and it only applies to metals.

Ohms law can be written as an equation:

R=V                V=IR                 I=V

     I                                               R

This means if the resistance is 1 ohm it needs 1 Volt to drive a current of 1 amp through it.”-Class work

What effects resistance?

“There are four main factors which effect resistance they are:


*Wire length

*Wire width

*Material of wire”-Physics for you

I predict that if the length of the wire increases so does the resistance because the electrons have a longer distance to travel, causing more collisions to occur in the wire.

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From my pilot experiment I now know that the safest and easiest range to use is from 10cm to 90cm, for the final investigation I will increase the length of the wire from 10cm to 90cm in steps of 10cm. This will give me 9 different lengths.


*Set up the equipment as shown in the diagram on page one.

*Using the ruler measure a distance of 10cm between the crocodile clips, making sure the distance is in the exact middle of the crocodile clip. (If this is not done then the length will not be correct)

*Set the Voltage to 2V and measure the current from the amp metre and the other Voltage from the Voltmeter.

*Then change the voltage to 3V, then 4V doing the same as you did when using 2V.

*Once this has been done turn off the electric from the power socket and readjust the crocodile clips so the distance is 20cm, again change the volts from 2 to 3 and then to 4, measuring the current and voltage each time.

* Do this 9 times starting with 10cm and working up to 90cm, making sure the length is exact and the electric is turned off when adjusting the length.

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I think my investigation went very well. Using my method I have found out that as the length of the wire increases so does the resistance. I also managed as far as possible to measure the length and resistance accurately. The results on my graph are generally on if not very close to my line of best fit.

I feel that my results are as accurate as possible. I took three sets of results and averaged them. Each set of results were very close but again I cannot be 100% sure they are exact due to the experimental errors mentioned in my analysis I also noticed that the crocodile clips were approximately 3mm in width and I cannot be sure that the length was measured in the exact middle of them.

If I was to re do the experiment I would make sure the wire was stapled perfectly straight. I would take more results to average and I would use a wider range of volts, keeping in mind that the more volts used the higher the temperature of the wire would be and the greater the resistance put on the wire, which would effect my results.

If I followed all of these adjustments correctly I would expect more stable and accurate results so my results plotted on my graph would all be on if not closer to the line of best fit.

...read more.

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