# To investigate the resistance of a conducting material as its length changes.

Christopher de Wardt                                                         Dulwich College

## Planning

### Introduction

Aim: To investigate the resistance of a conducting material as its length changes.

I am carrying out this experiment to find out if as a result of changing the length of a conducting material – graphite paper in my case, the resistance changes directly because of this change. In order to make sure that the results, leading to further conclusions, are reliable, I must make sure that any other factors that could possibly affect resistance are kept constant.

### Variable Studied - Length

I will be using a circuit method in this investigation; there are a number of different factors that I must take into account when investigating the resistance of the graphite paper. Obviously, the first is length, which I will decrease from its starting length in equal steps as it approaches zero centimetres long; this is the main variable being considered in my investigation. The width of the paper must also be kept constant, as it may affect the results, and causing the investigation to become unfair.  To evaluate the resistance of the graphite paper I will record my observations in terms of voltage across the paper and the current of the circuit. Because of this, the potential difference will be maintained at a given value across the different lengths of graphite paper as it is the only variable I can modify directly (current, for instance, is a value depending on the potential difference throughout the circuit and its resistance as a whole). An increase in temperature increases the amount of collisions between atoms and electrons; this is the cause of resistance. Therefore, I must try and keep temperature as constant in my given – lab – environment to make sure that my results are fair. I am not sure how great an effect temperature has on the resistance of graphite, so I am conducting a preliminary experiment to find out to what extent I must control the temperature of the lab environment and how accurate my results can actually be.

### Introduction:

I know that graphite is a semi-conductor from personal knowledge; what this means in terms of resistance is that although the amount of collisions between electrons and atoms increases as the temperature increases – due to an increase of kinetic energy in the structure, causing vibrations and leading to more collisions – more electrons are released from the structure of the graphite as free electrons which ...