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Factors influencing the resistance of a wire
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What is Resistance? Resistance is caused by collisions between the atoms in the object and the electrons (carrying electricity), which are trying to move through the object. (R = resistance measured in ohms (W)). Basically resistance is the term used to describe an objects resistance to the flow of electricity Electrons lose their drift velocity only when they collide. The electrical resistance of a conductor is simply a measure of the potential difference required to maintain a current. Basically resistance is a representation of how many electrons are colliding, and how quickly. An electrical current is caused when free electrons moving through atoms are influenced by either a positive or negative charge. This causes all the electrons to change course. This is what we call an ‘electric current.’ We can work out resistance using Ohm’s law: Ohm's law states that the current in a metallic conductor is directly proportional to the potential difference across it provided the temperature is kept at a constant value. Resistance=voltage/current Hypothesis: I predict that the rules and factors mentioned in the hypothesis can be proved to be correct by the experiments. There are five key factors that affect the resistance of a wire. Temperature, Cross Sectional Area, Length, Insulation and Material. I am only going to investigate three of these factors, temperature and insulation being the ones I will not be investigating. In these diagrams the circles represent atoms , and the arrows the flow of electricity. Below is a comprehensive guide to how these different factors influence the resistance of a wire: 1. Length: The Longer a wire is, the more resistance there is. This means for example…that if a wire that is 2 metres long is compared to that of a wire that is 4 metres long, then the resistance of the second wire will be more or less double that of the first. That is if all the other factors were the same for example: both wires were 3 cm in diameter, 20 degrees Celsius and made of nickel. The reason for there being more resistance is that it takes a longer time for the electrons to flow down the wire, and therefore there is a greater chance of them colliding more. Think of a long motorway with a large amount of cars all trying to get to the same place at high speed- collisions are imminent. This means that the shorter the wire, the lower the resistance. See Diagram Below: Diagram 1 2. Cross sectional area: Diameter is another factor that can have influence over the resistance of a wire. A thick wire will have a lower resistance than a thin wire. This is because the free electrons effectively have more space to move round in, and therefore fewer collisions take place. Again, it can be thought upon as a congested motorway. Except this time the motorway is so large, that everyone can drive along quickly in their lane, and has no risk of collision. The larger the area, the more room there is for electrons to move round. The fewer collisions there are, the lower the resistance. See Diagram Below: Diagram 2 3. Material The material that the wire is made from can also affect the outcome of the experiment. The amount of resistance is not the same in every metal.
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