# The experiment I have chosen to carry out will record whether the length of a wire will affect the resistance in a complete circuit. I will set up an experiment, setting up a complete circuit

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Introduction

Physics Coursework

Investigating factors affecting resistance

The experiment I have chosen to carry out will record whether the length of a wire will affect the resistance in a complete circuit.

I will set up an experiment, setting up a complete circuit with a wire of length 1metre. I will then record the current and voltage at certain lengths of wire. From these two measurements, I can calculate the resistance using ohms law. I will take measurements every 5 cm of wire until I reach 30 cm, when I will measure every 10 cm instead.

The experiment will be carried out twice and the average of the two resistances (at each measurement) will be used.

I will need to use:

. 1 power cell – to create a source of power for the circuit

. 1 metre of wire – to measure the resistance from (diameter 28 SWG)

. Volt metre – To measure the voltage

.

Middle

Results:

Experiment 1:

Length of Wire (cm) | Current (Amps) | Voltage (volts) | Resistance (Ω) |

5 | 0.93 | 0.53 | 0.569892473 |

10 | 0.61 | 0.72 | 1.180327869 |

15 | 0.48 | 0.84 | 1.75 |

20 | 0.41 | 0.92 | 2.243902439 |

25 | 0.36 | 0.98 | 2.722222222 |

30 | 0.32 | 1.02 | 3.1875 |

40 | 0.26 | 1.1 | 4.230769231 |

50 | 0.22 | 1.17 | 5.318181818 |

60 | 0.19 | 1.22 | 6.421052632 |

70 | 0.17 | 1.28 | 7.529411765 |

80 | 0.15 | 1.31 | 8.733333333 |

90 | 0.14 | 1.33 | 9.5 |

100 | 0.13 | 1.35 | 10.38461538 |

Length of Wire (cm) |

Conclusion

The resistance increased because, as was mentioned in the prediction, resistance is a measure of how difficult it is to push electrons through a wire, so the larger the resistance, the more force you have to apply and the more energy you use to produce a current. This is why the voltage went up whilst the current went down.

The resistance of a wire is: R = r × L÷A.

L is the length of the wire, A is the cross-sectional area of the wire, (Of course, to get the most accurate results possible when applying this equation, we should make sure that the cross-sectional area of the full length of the wire is known.) and r is the “resistivity” of the material. Long, thin wires have the most resistance, just like long, thin pipes.

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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