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Investigate a factor that is responsible for affecting the resistance of a wire in an electrical circuit.

Extracts from this document...

Introduction

Physic’s Coursework – Francesca Gosling 11/3/02

Aim:

To investigate a factor that is responsible for affecting the resistance of a wire in an electrical circuit.

Background information:

Resistance: is the ability to resist the flow of electricity through it. Therefor a good conductor such a metal must have a low resistance and a poor conductor such as plastic must have a high resistance. The resistance is in control of the current flow, and so a high resistance will bound to have a low current and a low resistance will bound to have a higher current. I looked up the definition of resistance in the Hutchinson’s Encyclopaedia, It writes:

“In physics, that property of a conductor that restricts the flow of electricity through it, associated with the conversion of electrical energy to heat; also the magnitude of this property. Resistance depends on many factors, such as the nature of the material, its temperature, dimensions, and thermal properties; degree of impurity; the nature and state of illumination of the surface; and the frequency and magnitude of the current. The SI unit of resistance is the ohm (   ). Resistors are devices, as a coil or length of wire, used in a circuit primarily to provide resistance.”

Resistor: is a component in an electrical circuit used to introduce resistance to a current. Are usually made of wire – wound coils or pieces of carbon. Common examples of variable resistors are rheostats and potentiometers.

Georg Simon Ohm: From research on resistance I quickly found out that the German physicist was one of the forefathers of research into electrical resistance and is best know for Ohm’s law. He discovered that the force of a current travelling through a conductor is a measure of the current. The unit of resistance (ohm)

Middle

Results for 1st Experiment

 Length of wire / M Current / Amps Voltage / V Resistance / ohm 1.50 0.11 2.63 23.9 1.40 0.11 2.61 23.7 1.30 0.12 2.62 21.8 1.20 0.13 2.61 20.1 1.10 0.14 2.59 18.5 1.00 0.16 2.56 16.0 0.90 0.17 2.53 14.8 0.80 0.19 2.49 13.1 0.70 0.21 2.47 11.8 0.60 0.24 2.42 10.1 0.50 0.26 2.39 09.2 0.40 0.31 2.31 07.5 0.30 0.40 2.18 05.3 0.20 0.54 2.00 03.7 0.10 0.85 1.65 01.9

Results for 2nd Experiment

 Length of wire / M Current / Amps Voltage / V Resistance / ohm 1.50 0.11 2.65 24.1 1.40 0.11 2.65 24.1 1.30 0.12 2.64 22.0 1.20 0.13 2.59 19.2 1.10 0.13 2.58 19.8 1.00 0.15 2.57 17.1 0.90 0.16 2.54 15.9 0.80 0.18 2.52 14.0 0.70 0.20 2.49 12.5 0.60 0.24 2.43 10.1 0.50 0.29 2.35 08.1 0.40 0.33 2.28 06.9 0.30 0.40 2.16 05.4 0.20 0.48 2.09 04.4 0.10 0.50 1.83 03.7

Conclusion

Investigating the cross section width of the wire, I would need to prove that the resistance of a wire is inversely proportional to its diameter. For this experiment to work, one material will be needed, although several different diameters for this wire will also be required. The length of the wire will be kept constant through out the investigation to keep it a fair test. I would carry out the experiment out in the same was as I did when I investigated how length of wire affected resistance, but instead of changing the length in one piece of wire I would change the diameter of several pieces of wire.

If I extended my investigation further I would then investigate what affect it would have on the resistance if I change the material I am using. I would need to do an experiment to prove that different materials have different resistances. To do this I would need to choose tow materials, which conduct electricity, and test them against each other. This would then show me if their resistances were the same or not. From my background information I found out the two best materials to use is copper and nichrome wire. I will have to make sure the wires tested must be exactly the same length because other wise it will not be a fair test. I will find the resistance from 10 cm t0 1meter of wire for both the copper and nichrome wire. I would do this in the same way as I found the resistance for different lengths of wire; apart from instead of just changing the length of one piece of wire I am going to have to change the length for two different pieces of wire.

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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