Is it possible to have the value of relative permittivity less than one?
Answers
Explanation:
If a material had a relative permittivity less than 1 the charge stored would be less than with air/vacuum. the polarisation would have to be reversed so that the dielectric accumulated surface charge of the same polarity as the adjacent plate.
This separation of charge it isn't going to happen naturally in a material. it would require an external energy source to 'force' it's mobile charges or polar molecules to do this.
For this reason there isn't a material that inherently has a relative permittivity that is less than 1. However, covering a metal plate with a material of relative permittivity 0 on one side. Then place a charge on the metal plate. The system as a whole will accelerate towards the metal side since there is no flux on the covered side and so the charge is accelerated in the direction of the uncovered side. This is a violation of the conservation of energy principle, so it is impossible. Extending the argument to relative permittivity simply less than one instead of 0, there will be less flux on the covered side, so again the charge is accelerated in the direction of the uncovered side. So this must also not be possible. But we do have materials with relative permittivity greater than one, and I could use the same argument in that case. Why can I not, or why is it invalid to extend the argument for 0 permittivity to finite permittivity.