Investigating factors that affect the resistance in a circuit, specifically wire components.

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Factors effecting resistance

Aim: Investigating factors that affect the resistance in a circuit, specifically wire components. I will be discovering how thickness/diameter affects the resistance in a piece of wire by changing the diameter in each test.

Reason for choosing this factor: Thickness of wire is reliable to use because you can use thickness’s that are worked out accurately to 3 decimal places of a millimetre. These are worked out by computers and manufactured on mass, coiled on reels of various lengths. There is a vast selection of different thickness’ which have a common measurement called S.W.G.,(standard wire gage) relating to cross sectional area ie A/resistance. It is an efficient experiment to complete with reliable results.

  1. Length would be more difficult to use accurately as you would have to measure it by hand with a ruler or tape measure depending on length you are using. Because the wire is rolled onto a reel it will have bends and kinks in it, which are hard to straighten when measuring. IF you heated the wire up to soften it you could straighten but this takes effort and other equipment, which is not available.
  2. Material is an interesting factor to change as you can discover the resistance in different metals and how they compare with one another, however with the limited equipment in school we only have copper, nicrome and constantan in wire form. You cannot produce a sufficient graph that you can draw conclusions from with only three results as it would be impossible to identify if there are any anomalies.
  3. Temperature is a difficult variable to measure properly; the experiment would be hard to perform as it depends on heating the water to an exact temperature. The heating relies on e.g. a Bunsen burner heating the liquid, which will increase the energy between the particles making faster, and larger collisions, this energy transfer will vary all the time in speed and there fore heat.
  4.   In the experiment these other factors will need to be controlled and constant to ensure a fair test.

Prediction: I think that the thicker the diameter of the wire the less resistance will occur in the circuit. The reason being the thicker the path way is for the electrons the easy it is for them to travel through the static ions. They need less force to push them through, where as with a thin wire more are electrons are trying to push through a small space at one time, creating more friction and there fore more resistance. If we work out the cross sectional area of the wire there is a direct correspondence with the resistance. As the area doubles so will the amount of ions and electrons in the wire. This means there will be twice as many collisions between ions and electrons but also twice as many electrons managing to pass through these gaps. Resistance occurs by free electrons bumping into stationary ions.

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The movement of the electrical charge is called the current. The current is the rate the charge flows around the circuit. The more ‘push’ emitted from an electrical source e.g. battery, the larger the current. The current (I) is worked out by finding the charge (coulomb-Q) and the time,(t-seconds) and  dividing charge by time. A current flows in a metallic conductor by a battery or the mains forcing energy into a circuit creating a movement of electrons. The conventional current flows in the opposite direction to the –e.  

Most metals outside shell of electrons have relatively weak ...

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