EASY AND SIMLER PROJECTS ON ELECTRO-WRITING- Dip a filter-paper in a solution of sodium sulphate containing a little amount of phenolphthalein. Now keep this filter paper on a copper plate.
Join the positive pole of a battery to the copper plate with the help of a copper wire. Take a long flexible insulated wire and attach one end to the negative pole of the battery and attach the other with a metallic stylus.
Write anything on the blotting paper by pressing this stylus. We will get the writing material which we had wrote in red colour.
( This process can be used to test the negative or positive pole of a battery. The red colour will be get only by negative pole wire).