# Investigation on the Resistance of Nichrome wire

Extracts from this document...

Introduction

Lucy Kennington C2

Investigation on the Resistance of Nichrome wire

## Planning

## Variables

- Voltage
- Current
- Length of wire
- Apparatus used in the circuit
- Temperature of room
- Thickness of wire
- Temperature of wire
- Material that the wire is made from

Investigating how changing the length of Nichrome wire affects the resistance

## Apparatus

- 1000mm Nichrome wire
- 2 leads
- 2 Crocodile Clips
- Multimeter (Battery operated)
- 1000mm Ruler
- Thermometer
- Sellotape

Preliminary experiments

I carried out a preliminary experiment to find out which apparatus would be best suited to find the resistance of Nichrome wire, to see the other factors that could affect the experiment and also to see if I could improve any of the steps in the method.

I began by setting up two circuits, the first with a multimeter and the second with a power pack, I wanted to see which one would be more accurate for my investigation. Using a multimeter is more accurate because it keeps the current going through the circuit low which keeps the temperature of the wire just about the same, this means if the wire is not heated and so the particles of atoms and electrons will not collide as frequently which therefore will not convert as much kinetic energy into heat which could affect the results. The multimeter will have the same current because of the fuse, the fuse only lets up to 0.25A flow through any circuit, this is a low current so it will not give the wire a noticeable heating affect although there is very little temperature change, but it would not affect my investigation.

If I used the power pack to find the resistance of the wire I would have to wait for the wire to cool down in between each

Middle

As the cross-sectional area of the wire doubles, the resistance will half. There would be twice as many ions and twice as many electrons bumping into them, but also twice as many electrons getting through twice as many gaps. If there are twice as many electrons getting through, there is twice the current, the resistance must have halved. The thinner the wire is the less channels of electrons in the wire for current to flow, so the energy is not spread out as much, so the resistance will be higher: We see that if the area of the wire doubles, so does the number of possible routes for the current to flow down, therefore the energy is twice as spread out, so resistance might halve.

I think the graph will be like the shape I have drawn it because I predict the longer the wire the higher the resistance and because I think the resistance of wire will go up by the same amount each time. I think the graph will be straight in a diagonal line going to the right. The graph line does not go through the origin because even if I were to place the crocodile clips on the wire at 0mm there would still be a resistance because of the resistance of the leads. The graph would go through the origin if I took away the resistance of the leads and the crocodile clips, this would not give an accurate drawing of the graph though because when the crocodile clips are touching and connected in the circuit with the multimeter there will always be some resistance due to the leads.

Bibliography

(1) = Internet resources

Table of Experiment Results

Length of Wire (mm) | Thickness of Wire (mm) | Room Temp (˚C) | Voltage (V) | Current (A) | Resistance of Wire (ohms) | ||

1 | 2 | 3 | |||||

0-0 | 0.45 | 21 | 9 | <0.25 | 0.3 | 0.3 | 0.3 |

0-100 | 0.45 | 21 | 9 | <0.25 | 1.0 | 1.0 | 1.0 |

0-200 | 0.45 | 21 | 9 | <0.25 | 1.7 | 1.8 | 1.7 |

0-300 | 0.45 | 21 | 9 | <0.25 | 2.4 | 2.4 | 2.5 |

0-400 | 0.45 | 21 | 9 | <0.25 | 3.2 | 3.1 | 3.2 |

0-500 | 0.45 | 21 | 9 | <0.25 | 3.9 | 3.9 | 3.9 |

0-600 | 0.45 | 21 | 9 | <0.25 | 4.6 | 4.6 | 4.8 |

0-700 | 0.45 | 21 | 9 | <0.25 | 5.3 | 5.3 | 5.3 |

0-800 | 0.45 | 21 | 9 | <0.25 | 6.0 | 6.0 | 6.1 |

0-900 | 0.45 | 21 | 9 | <0.25 | 6.9 | 6.7 | 6.7 |

0-1000 | 0.45 | 21 | 9 | <0.25 | 7.4 | 7.4 | 7.5 |

Conclusion

I think I got those anomalies because of a wrong measurement when I was attaching the crocodile clip to the wire. I probably just made the increasing gap bigger than it should have been because the resistance between the two points were more than normal 0.7ohms.

If I had time the additional experiments which I would have carried out to be sure of my graph results would be longer length of Nichrome wire, to see if the graph would carry on in a straight line and increase by the same resistance each time and the resistance of the clips and leads would have been less significant.

I do not think there is another way to investigate the variable I did apart from changing the apparatus and using a power pack, digital voltmeter and ammeter instead of using a multimeter.

Things, which could affect the end result of my investigation, need investigating. Things that could affect my final results would be rusty old crocodile clips so I would have to test them to make sure they gave the correct resistance. I could do this by attaching two crocodile clips together in a circuit with a multimeter and if the resistance were different from 0.3ohms I would know that they are not giving me the correct resistance. I know this because in my preliminary experiment I did the same but with clean crocodile clips and they gave me a resistance of 0.3ohms. If I were using a power pack I would also need to investigate the heating affect. I would have to use a thermometer to check the temperature of the wire.

G.C.S.E Science Coursework

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