Hi, recently my class did an experiment to find the relative permittivity of polythene. I did some calculations by comparing the capacitance of 2 metal plates with air between them and the same capacitor with a sheet of polythene. It turned oout to be 1.57. However, I googled and it seemed to be 2.35 instead. Can you suggest what might actually have caused this error? There seems to be many possible reasons like slight fluctuations in the current or even increase of resistance in the wire due to heating but none seems to explain such a large difference.