Water and Uniform Electic Field I was wondering if water molecules align to a uniform electric field, since water is an electric dipole. And if so what are the consequences of that?
 A: They do align on average, but it's not an "all at once" type thing: they are all jiggling about a bit and only on average do you see that the dipoles point more and more in the direction of the field as the field gets stronger and stronger. The main consequence is that, as a result, light moves slower in water than it does in vacuum, which creates the reflections and refractions of light at water surfaces. That's not properly speaking a "uniform" electric field, but it is the most common way you'll see the response of water to electric fields.
A: Yes, they do align, making water what is called a "dielectric" material, a material that when one applies an electric field on them, the aligning of the dipoles in the material create an opposing electric field, making the net $\vec{E}$ smaller than the applied $\vec{E}$. This happens also to materials with molecules that don't have a dipole moment, the electrons in the atoms are a bit moved because of the $E$ field creating a little dipole which opposes the electric field.
Sorry for the English, I hope it helped!
