# An Investigation to find out how the length of a wire affects its resistance

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Introduction

Karan Kooner 10.8

An Investigation to find out how the length of a wire affects its resistance

Scientific Enquiry:

I know that metals are good conductors of electricity. Metals are good conductors because their electrons are easily released allowing electricity to flow.

The electrons can carry current because they split up from the positive ions, so they are free to move and to carry current.

Factors that affect resistance:

- Length – the longer the wire the more atoms there are for the current to push through.
- Width – there is a greater collection of atoms.
- Material – Different materials have different atom structures so resistance varies.
- Temperature – the hotter it is the harder it is for current to get through.
- Voltage – the higher the voltage the more resistance there is.

Planning:

Aim:

The aim of this investigation is to find out how the length of a wire affects its resistance.

Prediction:

I predict that, as the length of the wire increases so will the resistance. I think this will happen because as the wire gets longer the current has more atoms to get through.

Middle

Method:

- Set up the power pack and connect power pack wire to crocodile clips.
- Place crocodile clips at 5cm on the nichrome wire.
- Take measurement of current and record in results table.
- Repeat the procedure at 10cm, 15cm, 20cm, etc. until you get to 40cm.
- Repeat the method 3 times.
- Calculate average.
- Calculate resistance using the equation: resistance = voltage ÷ current.

Fair test:

I am going to make this investigation a fair test by repeating the experiment on each length 3 times. I will then work out an average and a resistance (using the average) for each length.

Variables:

In this investigation I varied the length of wire by 5cms for each measurement. The current also changed because of the length of wire. As the length of wire increased the current decreased, this is because as the length of wire increased so the resistance.

Constants:

I kept the voltage at 2V, I used the same nichrome wire all the way through the experiment and the width of the wire remained at 0.2mm.

Safety Points:

I made this test safe by keeping the voltage at 2V. Any voltage higher will heat up the wire and cause it to melt.

Obtaining Evidence:

Initial results (includes errors):

Length (cm) | 1 | 2 | 3 |

5 | 0.33 | 0.33 | 0.33 |

10 | 0.20 | 0.19* | 0.20 |

15 | 0.13* | 0.14 | 0.14 |

20 | 0.10* | 0.11 | 0.11 |

25 | 0.08* | 0.09 | 0.09 |

30 | 0.07 | 0.08* | 0.07 |

35 | 0.06 | 0.06 | 0.06 |

40 | 0.05 | 0.05 | 0.05 |

Conclusion

Another investigation I could do which is related to the experiment is to how temperature affects resistance. I could record the resistance of a wire at different temperatures to see how large the effect is. I could also do a similar investigation to this one by increasing the width of a wire and not its length.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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