# Investigation into the Resistance in different lengths of wire

## Investigation into the Resistance in different lengths of wire

Introduction

In this investigation, I will be looking at how the resistance in a piece of wire changes when I change the length of the wire. The variable in the experiment will be the length, and the thing I am studying will be the resistance.

Equipment

• For my experiment I will need:
• Wires of set length - for connecting the circuit together
• A Variable Power Pack - to give the experiment its power and so that I can adjust the current to a suitable level
• Wire that I can cut and adjust - this is the wire I will be testing though, so it must be bare.
• Crocodile clips, to secure the wire
• Voltmeter - to measure the voltage
• Ammeter - to measure the current

Diagram

A

V

Method

I will set up the experiment as shown above, and then connect the 100cm wire to the crocodile clips, and turn the power on. Then I will take a reading of the Ammeter and Voltmeter, and record them. Then I will remove this wire, and replace it with a 90cm long wire, take a reading, and remove it. I will do the same for the 80cm, 70cm and so on, until I have reached 0cm. I have decided to use wire at 10cm intervals because it gives a nice even spread over the 100cm range, and it is small enough for me to see where anomalies are. So this means that if anything goes wrong, I can easily see it.

I will repeat the experiment three times to make sure that none of my results are way off the mark. If I find that there is an anomaly somewhere in my results I can identify it easily and redo that part of the experiment. This will also help in keeping my investigation fair.

Fair Test

To keep my experiment a fair test, I can do many things. I will repeat my experiment three times, so that I know that my results are not ‘dud’ ones. I will use the same type of wire all the way through the experiment, as different types of wire will have different amounts of potential for resistance depending on their makeup - i.e. what metals are used, the amount of impurities in the wire, etc. I will also keep all the settings on the power pack the same as well, because this would seriously affect my results if I changed the power going into the circuit in any way. I will also keep all the other equipment the same, seeing as there is nothing that needs to be washed such as there might be in a chemistry experiment or similar.

There are variables that I cannot control, such as the temperature in the room. The only thing I can do to combat this is to do my experiment all at once on one day, and hope that the temperature does not fluctuate too much. Human error is another unavoidable variable seeing as we cannot get a robot to cut the wire! To minimise this, one person will cut the wire, and use the same ruler to do it on throughout the experiment.

If I stick to these rules, there should be no need to repeat any parts of the investigation, ...