Investigating resistance.

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KS4 Coursework PHYSICS               2003-2005

INVESTIGATING RESISTANCE  

                                                                                         Beth Davison

P                                                                        10A 1ss

O                                                                    Llandrindod Wells High School

A                                                                    Mr D.J. Lewis (P1)

E

Preliminary Work

                      An example of using the term resistance in every day language is to resist eating chocolate. This means to stop yourself from eating chocolate or to cut down the amount of chocolate eaten.

        According to “Usbourne Illustrated Dictionary of Science” resistance (R) is the ability of an object to resist the flow of current. The unit of resistance is ohm (      ). It also says that a resistor is a device with a particular resistance value, used to produce a required potential difference.

        Good conductors have low resistivity (the ability of a substance to resist current) and insulators have high resistivity.

 

Prediction

              I predict that when I add more resistors in a parallel circuit the resistance will decrease because if I made two holes in the bottom of a bucket rather than one the water in the bucket would flow out twice as fast.

        I also predict that when I add more resistors in a series circuit the resistance will increase because if I walked down a short corridor and then I walked down a long one  it would take me a longer time to walk down a longer corridor. So, metaphorically, each time I add a resistor the “corridor” gets longer.

Plan

          1)                                                                   A Series Circuit

           

                                                                with one resistor

                                                                

                                                                with two resistors

  1. A Parallel  Circuit

                                                        with one resistor

                                                        with two resistors

For both circuits I will repeat the experiment for up to five  resistors.

Results

         

Series Circuit                                              Parallel Circuit

     

                   No. of          Resistance                                  No. of          Resistance

                 Resistors                                           Resistors

  1.            1.26                                             1               0.92
  2.            0.78                                             2               1.16
  3.            0.60                                  3               1.22
  4.            0.50                                  4                   1.28
  5.            0.42                                  5                   1.33
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What Factors Affect the Resistance of a Wire in a Circuit

The four factors which will affect the resistance of a wire are :

  • Thickness
  • Material
  • Length
  • Temperature

If the wire were thicker there would be more space for electricity to pass through.

If the material changed it would have a different density so there may be more particles in the way of the electricity current.

If the wire is quite long then it takes a longer amount of time for the electricity to pass through.

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