What is the effect of voltage in water from batteries?

The effect that you get when you apply voltage from a battery to water is bubbles. the bubbles are caused by the hydrogens and oxygens seperating. to get more bubles there are a number of things you can do. 1st if you add salt to the water it will bubble more as well if you attach two 9 volts together and add the salt you get even more bubbles and the last thing you could do is rap your wire around graphite rods which you can get out of pencils if you feel like shaving the wood off but any way i hope i answered your question.