relative permittivity

what is the effect of relative permittivity in respect to current.air has low and water has high relative permitivity.how does it affect the electric field.

Hy,
Thirstly,the permittivity (eps)is introduce to connect E to D (Electric displacement) in the Maxwell Gauss equation. If you look at Capacitor, you can store more electric load if eps is high.
Secondly, eps appears in the Maxwell-Ampere equation with the displacement current : d/dt(D). And also, bring together with Maxwell -Faraday equation,we can determine the velocity of light which is : 1/sqrt(eps * mu). So velocity of light depend on eps and consequently wavelenght too.
Moreover, if the eps has a complex part, loss will appear in the propagation of the wave.

That's all for the moment but you can read some good books deal with this subject.

Bye.