An investigation to find out the factors that affect the resistance of a wire

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Science Investigation

An investigation to find out the factors that affect the resistance of a wire

Name: Sheena Bheeroo

Candidate Number: 7226

Centre Number: 15215

Centre Name: Ashcroft High School

Year: 10

Set: 1

Date:

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PLANNING

Aim:

As the title suggests, what I intend to do in this experiment is find out what factors will affect the resistance of a wire. For example, if the length of a wire is shortened, then will the resistance increase or decrease.

Fair test:

In order to make this experiment a fair test, to obtain reasonable results, only one thing can be changed. All the other factors/variables would have to remain exactly the same. For example, if the length of the wire were being decreased at a reasonable measurement range then that would be the only thing that should be changed. The type and thickness and voltage should not changed, otherwise that could affect the results obtained.

Safety

As in every scientific experiment, safety precautions must be followed. The safety measures to be taken here are as follows:

* A heatproof mat must be placed underneath the wire, in case the wire gets too hot.

* Do not hold the wires with hands. Always use the crocodile clips, as the wire would most definitely burn your hands if it got too hot (especially when the wire is below 30 or 40 cm, as these are the measurements when the wire could overheat).

Apparatus:

* Power pack

* 5 connecting wires

* 2 crocodile clips

* Digital ammeter (gives more accurate results)

* Analogue voltmeter

* Heatproof mat

* Wires (different length, thickness and type)

Diagram:

Method:

* Set up the equipment as shown in the above diagram, making sure the heatproof mat is under the wire.

* Draw a rough table to record the results.

* Clip the crocodile clips to each end of the wire. Remember distance between them should be 1 meter.

* Switch on the power pack and take the readings from the digital ammeter, connected in series and analogue voltmeter, connected in parallel. Remember to keep voltage the same throughout the experiment to make it a fair test.

* The power should be turn off while results are being recorded so that the wire does not overheat and burn.

* Decrease wire by 10cm.

* Repeat the previous steps until wire is only 10cm and you have 10 readings.

* You must have at least 6 readings so you can use them to plot a graph.

* Don't worry if when you get to the measurements of 30cm or below, the readings seem a bit peculiar, as at that point the wire might overheat and jump off the readings.
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* Make a neat copy of a results table and plot a graph, showing the line of best fit.

Prediction:

I predict that as the length of the wire decreases, the resistance will decrease. Therefore as the wire length increases, the opposite will happen and the resistance will increase because the resistance has more atoms to collide with. The reason I predict this is because long wires have more friction, resistance is increased; the less the current will flow. If the thickness of the wire is changed, then I predict that the thicker the wire, then ...

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