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Resistance Investigation

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Introduction

Resistance Investigation Aim: To investigate the factors affecting the resistance of a wire varying the length and the voltage and the type of material used. Plan: Equipment: * Meter ruler * PSU * Amp meter * Voltmeter * Multi meter (used as Ohmmeter) * Croc clips * Wire, 100cm+ of Nichrome Scientific Knowledge: The scientific knowledge is based on Ohm's law, which states then relationship that the amount of steady current through a large number of materials is directly proportional to the potential difference, or voltage, across the materials. Thus, if the voltage V (in units of volts) between two ends of a wire made from one of these materials is tripled, the current I (amperes) also triple; and the quotient V/I remains constant. The quotient V/I for a given piece of material is called its resistance, R, measured in units named ohms. The resistance of materials for which Ohm's law is valid does not change over enormous ranges of voltage and current. Ohm's law may be expressed mathematically as V/I = R. That the resistance, or the ratio of voltage to current, for all or part of an electric circuit at a fixed temperature is generally constant had been established by 1827 as a result of the investigations of the German physicist George Simon Ohm. Alternate statements of Ohm's law are that the current I in a conductor equals the potential difference V across the conductor divided by the resistance of the conductor, or simply I = V/R, and that the potential difference across a conductor equals the product of the current in the conductor and its resistance, V = IR. ...read more.

Middle

This means that the electrons have more difficulty getting through the wire as they collide with the atoms, which are in their pathway. This increases the amount of collisions therefore there is more resistance. However, it is hard to keep the temperature the same as the room temperature might change from day to day. It is essential to use a low voltage because it means a low current that will not heat up the wires. If a high voltage is used the energy would be in form of heat which would make the experiment unfair. The investigation will be done at room temperature. The temperature cannot be investigated because it is hard to control the range of temperature needed without the correct apparatus. 2. The larger the length of the wire, the larger the resistance. This is because there are more atoms from the metal so there is more chance that the electrons would collide with one of the atoms therefore there is more resistance. It is important to keep the length of the wire the same each time otherwise it could not be certain which variable is changing the resistance. The length of wire will be 50cm throughout the investigation. Electrons have a longer distance to travel so there are more collisions .The length of the wire will make a difference to the resistance. This is because when you have a long wire, the electrons have to squeeze together for longer to be able to pass through the wire than they do in order to be able to pass through a short wire. ...read more.

Conclusion

I know this because the Line of Best Fit is a straight line through the origin showing that if the length of the wire is increased then the resistance of the wire will also increase in proportion to each other. The line of best fit is a straight and it goes though (0, 0) if there is no length, there is no resistance proving that the resistance of the wire is directly proportional to the length of the wire. This proves my prediction is correct. I can work out the resistance of the length by finding the gradient of the line. The length of the wire affects the resistance of the wire because the number of atoms in the wire increases or decreases as the length of the wire increases or decreases in proportion. The resistance of a wire depends on the number of collisions the electrons have with the atoms of the material, so if there is a larger number of atoms there will be a larger number of collisions that will increase the resistance of the wire. If a length of a wire contains a certain number of atoms when that length is increased, the number of atoms will also increase. If the wire is half the length of a certain wire, it would have has half the number of atoms, this means that the electrons will collide with the atoms half the amount of times. In addition, if the length of the wire was trebled or quadrupled, then the resistance would also treble or quadruple. Evaluation: Weiran Zhang 11AK 20/12/01 Page 1 of 6 ...read more.

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