# My investigation into the length of wire and the effect it has on resistance.

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Introduction

Sally Bryan 10B22nd May 2004

My investigation into the length of wire and the effect it has on resistance

My investigation is to see how the length of wire and resistance are related, to see what length of wire has what resistance. Resistance has four variables, one of these variables that effects resistance is the length of the wire. The other variables are the thickness of the wire, temperature and also the material type. In my investigation, I will use constantan wire which will be 0.28mm thick. My input variable is the length of the wire. Throughout this investigation, I will change the length of the wire and record what effect it has on the resistance. The output variable is voltage (V) and current (I); from these I will calculate the resistance.

Resistance= Voltage/Currentor R=V/I

Resistance is the variable that reduces the flow of current in a complete circuit.

Model 1 Particles in a length of wire

Electrons flow from negative to positive, due to them being negatively charged. They flow in the opposite direction to the Convectional Current I.

Middle

TRIAL 2

20cm

30cm

40cm

50cm

60cm

70cm

80cm

90cm

100cm

Voltage

0.22

0.32

0.39

0.47

0.58

0.64

0.73

0.85

0.92

Current

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

Resistance

2.2

3.2

3.9

4.7

5.8

6.4

7.3

8.5

9.2

TRIAL 3 | 20cm | 30cm | 40cm | 50cm | 60cm | 70cm | 80cm | 90cm | 100cm |

Voltage | 0.21 | 0.31 | 0.41 | 0.48 | 0.57 | 0.66 | 0.75 | 0.85 | 0.91 |

Current | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 |

Resistance | 2.1 | 3.1 | 4.1 | 4.8 | 5.7 | 6.6 | 7.5 | 8.5 | 9.1 |

Also, for my results on the length of wire against resistance, I have included a line graph for my 3 trials.

The mean Value of resistance (R mean) is calculated using:-

Conclusion

- Generally in copper wire, the resistance of wire is defined by the wire thickness and length and the nominal resistance of copper.
- Same applies also to wires made from other materials.

My output variables are voltage (V) and current (I), from these I will calculate the resistance.

Resistance=Voltage/Current or R=V/I

My prediction is the same as in my last investigation:-

- If we double the length of wire, then the number of particles doubles.
- Therefore the number of collisions doubles.
- Therefore the resistance doubles.

In this investigation, I do not know if I will get similar results to those of my previous test. Copper wire may have a higher resistance than the constantan wire, or vice versa. One wire may be a better conductor or insulator than the other; this would cause the resistance to either increase or decrease.

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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