I am conducting an experiment to find out how the length of wire affects resistance.

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Science Coursework

Resistance

Introduction

I am conducting an experiment to find out how the length of wire affects resistance. The experiment I am conducting is passing an electric current through a wire made of constantan. I will take readings of the voltage and the current to find the resistance change when the length of the wire used is changed. I will be keeping the current and the voltage the same to obtain the results I want. The current will been kept unvaried by the use of a variable resistor. What I will be changing to find out about resistance is the length of the wire, 100cm – 10cm. I will work out the resistance of each experiment by use of ohms law, and I will repeat each length 3 times.

Method

To do the experiment I will first set up all the equipment (diagram below). The power pack will be set to 8volts and I will keep the current at a constant reading. To do this I will vary the variable resistor on each length change. I will connect all the equipment and turn on the electricity. I will then take a reading of the voltmeter. I will then change the length of the constantan wire by moving the crocodile clips down the wire to the length that is needed. I will then turn the power on to adjust the current flow. Once I have adjusted the current to the same reading as the length before I will turn the power pack on at the same voltage and take the reading on the voltmeter. I will do each of these experiments 3 time, I will also take readings for each length from 100cm to 10cm also taking the reading of each 10cm in-between e.g. 100cm, 90cm, 80cm and so forth. Each time I change the length of the wire I must alternate the variable resistor to assure the current is the same reading each time.

Equipment list:

  • Power pack
  • 105cm of constantan wire (extra 5cm for placement of crocodile clips)
  • connecting wires
  • Variable resistors
  • Ammeter
  • Voltmeter
  • Meter stick
  • Crocodile clips

Safety

To make this experiment safe I must be aware of the electrical current that will be around me. I must make sure I use the equipment safely and in the correct manor. I will plug in the power pack with the mains switch off, and wait until power is needed before I switch it on. I must be aware of the heat that can be produce by the constantan wire when an electric current is running through it and be wary when the current is left running through it for a long period of time or is at a high voltage.

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Fair testing

To make this experiment fair I must only change on aspect of the experiment. I will be changing the length of the wire and nothing else. All other aspects will stay the same for the duration of the experiment, such as voltage and current. If more than one aspect were changed the experiment would not give accurate results and would be of no use.

Diagram of experiment

The experiment will work by electricity passing through the constantan. The ...

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