To investigate the factors affecting the resistance of a piece of wire.

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Natasha Brilliant

Investigation into the Factor(s) that Affect the Resistance of a Piece of Wire

The purpose of this investigation is to investigate the factors affecting the resistance of a piece of wire.  In order to investigate these factors I will need to carry out a series of experiments.  I will also need to research some background information using secondary sources.  I will then need to consider the equipment that I will use and the number of readings I will take for each experiment.  I will need to finally try to ensure that my results are as reliable and precise as possible while considering the safety aspect of my experiments.

Electrical resistance is a quantity which measures the amount of opposition a circuit or individual component provides to the electric current (charges) trying to flow.  The amount of resistance in an electrical circuit determines the amount of current flowing for any given voltage applied to the circuit.

The unit of resistance is the ohm, discovered by the German physicist, Georg Ohm.  One ohm is the amount of resistance that limits the current to one ampere when one volt is applied to it.  The standard symbol is R and the symbol for ohms in electric circuits is the Greek letter omega, Ω.  

Electrical resistance is inversely proportional to electrical current.  This means that if one doubles, the other halves or if one triples, the other decreases by a factor of three.  It is written as I ∝ 1/R with I being the symbol for current and R the symbol for resistance.  

The resistance of a wire is determined by four main factors:

  1. Length

The length of a piece of wire is related to its resistance.  I predict that the longer the wire, the higher the resistance as the electrical charges have further to ‘travel’.  Using a simple example will demonstrate this more clearly: if a person (representing the charge) is required to travel through a tunnel (representing the wire), which is so small that they cannot stand up, they will obviously find it easier travelling through a shorter tunnel than a longer one.  This is the same for the electric charges travelling though the wire – the shorter it is, the easier it is to travel through.

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  1. Cross-sectional area

I think that the larger the cross-sectional area, the lower the resistance.  Using my pervious example of the person and the tunnel we can see why: it would be a lot easier for the person to travel though a larger tunnel where they could stand up as opposed to a narrower one where they could only crawl.  It is therefore, I think, easier for the electrons to travel though a wire with a bigger cross-sectional area.

 

  1. Type of wire

Some wires are much better conductors than others are.  For example, copper is a ...

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