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The resistance of 'nichrome' wire.

Extracts from this document...

Introduction

Aim of investigation

I am planning to investigate the resistance of ‘nichrome’ wire, which is found in all electronic circuits, such as electric fires, kettles and toasters. All of these heating elements are made of thin nichrome wire.  As all conductors have some resistance, I plan to prove if there is any relationship between the resistance of the wire and the conditions and situations it is placed under.  I am looking closely at the resistance of the wire (nichrome) and to see how much it will change as the length of the wire is shortened.

What is resistance?

Electricity is conducted through a conductor, in this case wire, by means of free electrons. The number of free electrons depends on the material and more free electrons means a better conductor, i.e. it has less resistance. For example, gold has more free electrons than iron and, as a result, it is a better conductor. The free electrons are given energy and as a result move and collide with neighbouring free electrons. This happens across the length of the wire and thus electricity is conducted. Resistance is the result of energy loss as heat. It involves collisions between the free electrons and the fixed particles of the metal, other free electrons and impurities.

...read more.

Middle

Investigation

In this investigation we will encounter several variables: length, thickness and type of material.  When I investigated how resistance changed with length. I used nichrome wire; I kept the same thickness of wire but changed the length during the experiment.

The steps of my experiment are listed below:

  1. Obtain my equipment
  2. Set up the circuit (making sure everything is done safely, by checking that the nichrome wire is not short circuiting, the bench is dry and that the nichrome wire is not touching the bench.)
  1. Put the nichrome to the test by taking results off the voltmeter and ammeter when the length of the wire is at different lengths.  I will record the results in a table from the readings taking of the ammeter (0-5) and voltmeter (0-10).
  1. Plot the graph for resistance against length.

Before doing the experiment I predict that the longer the wire the greater its resistance.  The reason for this being the electricity has further to travel and has a lot more atoms to pass in doing so.  

In my experiment, I will use the following apparatus: Battery, voltmeter 0-10, amp meter 0-5, leads and crocodile clips, nichrome wire of different lengths between 0.4m to 1m in intervals of 10cm.

This is a diagram of the apparatus in circuit form:

Predictions

  • The 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.
...read more.

Conclusion

I do not think that doing any more results in our experiment would have made it any more accurate. Another way I could have made my results more accurate would be to use a different method – perhaps if i had a bar that did not bend in place of the wire. We could even use a rheostat in place of the wire, because it is essentially a long coiled wire that is connected at different lengths to change the resistance of the circuit.

Overall I feel my results are fairly accurate and I am happy with the outcome of my experiment.

...read more.

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