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# Resistance of a wire

Extracts from this document...

Introduction

Resistance of a wire

My task is to design and carry out an investigation to see how one variable effect’s the resistance of a wire.

In my experiment I am going to change one variable. This variable is going to be the length of the resistance wire to see how it affects the current and resistance. To get accurate results for my experiment and to keep it fair I must keep the other variables the same. So, I am going to keep the following the same;

1. The cross-sectional area of the wire (thickness).
2. The material that the wire is made from.
3. The temperature of the wire.

The thickness of the wire could change the amount of atoms in it giving it a higher or lower resistance. The material of the wire must also be kept the same because some materials are denser than others. The temperature is very important to keep the same. When a current is passed through a wire the electrons collide with the atoms inside the wire. Each collision produces heat. When an atom is heated it starts to vibrate. It is therefore moving, on a fixed point, but moving. This movement from side to side blocks the electrons creating more resistance. Chances are that there will be more collisions and so more heat and the process starts again (See Diagram Below). However if I only use a small current, maybe less than 1 Amp this may reduce the heating effect.

Middle

I predict that as I increase the length of the wire the resistance will also increase in the circuit.

Theory

I got this information from ‘

Resistance is based around the idea of ohms law, which states

“The electrical is a given conductor is directly proportional to the potential difference applied, provided that the temperature of the conductor and its other physical factors remain constant”.

This means that when the temperature of the wire is constant and the voltage is varied along the wire and the current may be lower. Resistance is represented by the symbol Ω which is the great letter omega = ohm.

The amount of resistance varies from small values to bigger values depending on the appliance. A copper wire for example is measured in a resistance of 1/100 Ω where as something like a radio or a T.V has that of millions of Ohms. Engineers have thought up fundamental formulas for calculating Current, Voltage, and Resistance.

Resistance = Voltage

Current

OR    I = V               OR    V = I * R

R

These are how the resistance of a wire/circuit/appliance are measured or vice versa, by using the definition R = V/I. This is the formula I will be using in the investigation.

In my science investigation I am investigating length of wire, the things I will keep the same are the thickness of the wire, the temperature of the wire. By doing these I will make my investigation fair. The thickness of the wire I will be using will be: 13457

Conclusion

Evaluation

The results I obtained from my experiment were quite accurate. The only two that were very slightly out were at the lengths of 50 cm and 80 cm. I think this was due to inaccurate measurement of the length of wire. One millimetre either way of the stated interval could make a difference. My results are still accurate and reliable enough to be used to form a conclusion and to show that my experiment was a success. I used sensible length intervals and I gathered enough results to form a conclusion and to find a pattern. I found that as the length of the wire increased so did the resistance.

During the experiment I encountered no problems with any of the equipment and I had no problems in getting the equipment I required. Everything went according to plan, I had plenty of time and I used it wisely. If I could do the experiment again I would measure the length of the wire and ask somebody for a second opinion. In doing this I might have removed the slight anomalies. Also I would have done the experiment with the same variable but change the temperature of the wire.

To extend the enquiry further I would investigate other things that affect resistance such as thickness of the wire, material of the wire and temperature of the wire. If I did this I could collect all the results together and see which variable had the greatest effect on the resistance.

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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