# Resistance Essay

4280 Words18 Pages
Investigating the resistance of a wire Aim: to design and carry out an investigation to examine how the resistance of a wire is affected by the length, material and cross sectional area. Introduction: What is resistance? Resistance of a metal wire is it’s to resist the flow of electrical current. A wire resists electrical current because of collisions between the free electrons and the fixed atoms of the metal, other free electrons and impurities. These collisions slow the electrons down and convert some of the energy that the free electrons are carrying into heat energy. The number of free electrons depends on the material, the length, the temperature and the CSA. A wire with more free electrons means it is a better conductor, which means it has less resistance. The bigger the resistance, the smaller the current. How is resistance measured? The resistance of a length of wire is calculated by measuring the current present in the circuit (in series) and the voltage across the wire (in parallel). These measurements are then applied to this formula: V = I ´ R where V = Voltage, I = Current and R = Resistance This can be rearranged to: R = V I Different materials of wires have different resistance to the flow of current through them, which occur because of physical differences in the wires themselves. This reaction that is being investigated gives off CO2 as a gas, so the rate of reaction could be measured with various techniques to measure how long it takes for a certain volume of carbon dioxide to be collected from the reacting solution. These methods include: taking measurements of the volume of gas given off; measuring the time taken for a precipitate to form; and taking readings of the mass of the reaction solution as a gas is given off. The results from this will make it possible to