760 words - 3 pages

TaskTo investigate how the resistance of a wire is affected by the length of the wire.TheoryWhat is resistance?Resistance is a force which opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long.e.g. The filament across an electric light bulb.How is it 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:Gradient = resistanceV = I x RThe other ways of writing Ohm's Law are:R = V/I or I = V/ROhm's LawIt is also relevant to know of Ohm's Law, which states that the current through a metallic conductor (e.g. wire) at a constant temperature is proportional to the potential difference (voltage).PredictionsThe longer the wire, the higher the resistance. This is because the longer the wire, the more times the free electrons will collide with other free electrons, the particles making up the metal, and any impurities in the metal. Therefore, more energy is going to be lost in these collisions (as heat).Furthermore, doubling the length of the wire will result in double the resistance. This is because by doubling the length of the wire one is also doubling the collisions that will occur, thus doubling the amount of energy lost in these collisions.VariablesIndependent variable - length of wire. I'll do six different readings, varying the length in each reading.Dependent variable - what you'll measure. I'll measure the resistance in each reading.Controlled variable - thickness of wire. Type of wire and temperature of wire.Length of wire - Increasing length of wire, increases resistanceMaterial of wire - A nichrome wire has more resistance than a copper wire of the same dimensions.Temperature of wire - In metal conductors, resistance increases with temperature. For semi-conductors, resistance decreases with temperature.ApparatusVoltmeterAmmeterBattery cellsResistorWire1 metre ruler with nichrome wire attachedMethod + Circuit DiagramThe following circuit was constructed to perform the investigation:1. Collect apparatus2. One metre length "nichrome" wire is fixed to a metre rule.3. The...

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