# Find out what affects the resistance of a wire.

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Introduction

Find out what affects the resistance of a wire.

Plan

The aim of this investigation is to find out what and how affects the resistance of a wire. To carry out the experiment I will need to build a circuit. In it I will measure the current it the circuit and voltage across the wire. I will need the know the current and voltage because:

Resistance (Ω ) =Voltage (V)

Current (A)

So to find out resistance of a component you have to know the voltage and the current. Therefor I will need to measure them both in my circuit with an analogue meter to measure current and an analogue meter to measure voltage. Analogue meter can give more accurate results than an ammeter or an voltmeter, so I will use it instead. The list of apparatus I will need, to do the practical must include all of this:

- Lab pack (will supply the energy in the circuit).
- 5 leads (will be needed to connect the circuit together).
- 2 crocodile clips (to clip on the on both sides of the wire).
- 2 analogue meter+two shunts (1 to measure current and 1 to measure voltage).
- Heat prove mat[s] (to protect the table if the wire overheats).
- Wire[s] will be a component who's resistance will be recorded.
- 1 meter ruler (to be able to measure to wire).
- Wire cutters (to cut the wire into different pieces i.e. 5cm--40cm).

There are different variables, which could change the resistance of a wire. I think that there is four variables which could be investigated:

- Thickness of the wire,
- Length of the wire,
- Material the wire is made out of and
- Temperature of the wire.

Middle

3

00.22

More then 10

Normal

Bare copper (length 40 cm) | |||

Voltage supplied (V) | Voltage across the wire (V) | Current in circuit (A) | State of wire |

5 | 1 | More then 10 | Normal |

4 | 0.6 | More then 10 | Normal |

3 | 0.4 | More then 10 | Normal |

2 | 0.3 | 7.60 | Normal |

Where it says “more then 10” , the current measured more then ten but because I had an analogue meter which measured up to ten, I was not able to get an exact answer. The state of wire column shows if the voltage supplied was too big or not. After doing this preliminary work I can not add more details to my plan. First of all I decides to look at how resistance changes in a nickel chrome wire that is 0.5cm thick. This is because bare copper's voltage results are very similar when I recorded it at the different length and because I cannot measure more accurately then to on decimal place my results will not be accurate. So after deciding to use nickel chrome I thought that 3 volts of supply would be sensible to use. This is because at 5 volts the wire heats up to the condition when temperature could effect the results. I also tested nickel chrome piece of wire 5cm and 40 cm long and it did and it was fine at 3 volts so the middle length will not cause any problem. The final desigeon I had to make was which shunts I will use with the analogue meter. I thinkt that the best shunts to use would be: an 0-5 (V) to measure voltage and 1-10 (A) to measure current.

Prediction

I think that there will be correlation or a pattern between length of a wire and resistance of a wire.

Conclusion

I think there is many ways in which this investigation could be expanded. However one of the most promising is if the extent ions which could be carried out is the study of all other factors that influence resistance. This are all the variables I had listed at the beginning. Thicker or area of cross section will be a good one to start of with because the results for that will be the opposite and the graph would show negative correlation, if the results gathered would be correct. It will be important to use wire out of the same material. After doing this it would be suitable to investigate the affects of temperature on resistance, this will much harder and will reqier more time time and equipment. After this the final part of the investigate could be carried out. I would be possible to test wires maid out of different material but with the same dimensions. Some of the elements could be used in the tests and then an order of resistance could be assembled, from lest resistant to most resistant.

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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