Why don't the leaves of an electrometer repel each other in water? A normal electrometer filled with air will repel like it should do for electrostatic demonstration, but what if it is filled with water instead or even oil, what will happen? 
My guess is that the water is charged too, making the net repelling force equal to zero.
But what will happen if it is filled with oil or another liquid?
 A: Here, we shall discuss about relative permittivity $\epsilon_r$. Permittivity $\epsilon_s$ of a substance is the measure of the resistance offered by a substance against the flow of electric field lines. Greater the value of $\epsilon_s$, fewer will be the number of electric field lines flowing through the substance. $\epsilon_r$ is defined as the ratio of the permittivity of a substance to that of vacuum or free space.
$\epsilon_r = \frac{\epsilon_s}{\epsilon_0}$
$\epsilon_0 = 1$
Observe the diagram below,

Now observe the diagram below,

In the case of olive oil, you see that the leaves are not well separated from each other. That is because, olive oil allows less number of electric field lines to go through it. This results in a decrease in the electric field strength and thus the electric force of repulsion.
In the case of olive oil,  
$\epsilon_r = 3$
Therefore, $\epsilon_s = \epsilon_r\times\epsilon_0$ which is 3. 
Clearly, permittivity of olive oil is greater than the permittivity of vacuum. As a result olive oil allows fewer electric field lines through it. Why? That's due to polarization effects taking place in the medium which in this case is olive oil. Polarization effects decrease the electric field strength in the substance. 
Besides relative permittivity, viscosity affects the separation between the leaves. Greater the viscosity, very little will be the separation between the leaves of the electrometer.
The above explanation is true in the case of water.
A: There are a few options.:
A) the liquid is a conductor and the electrometer is discharged. 
B) the liquid is non conductive, but it's viscosity is too high, so the leaves will not move 
C) if the viscosity is low enough, the leaves will move 
In normal water you will get A. 
As coulomb forces are usually not that big, in an insulating liquid B is most probable. 
A: If the electrometer leaves are wetted by the liquid, capillary forces (wicking) will pull them together and not allow them to easily separate.
DOI: 10.1021/la902779g 
DOI: 10.1109/84.232594 
DOI: 10.1021/ja983882z 
http://web.mst.edu/~numbere/cp/chapter%203.htm 
   3.1.4 Application to Parallel Plates
Take two clean microscope slides, immerse them in clean water, press them together.  Normal separation forces exceed the strength of the glass.  Parallel separation by shear requires considerable force.  Electrometer leaf electrostatic forces will be irrelevant up to considerable charge loadings.
