Electronix

Human body has an electrical resistance of about 1 Mega ohm. When our skin is dry, it can be more and when it is wet (from water or sweat etc) it can be lesser. This lie detector detects the resistance of our skin and plays a sound according to it. Lesser the resistance, higher the pitch of the sound played by the speaker. When we tell a lie, we feel nervous and sweat, therefore our resistance decreases which is shown by the increasing pitch of the sound from the speaker. A SCHEMATIC DIAGRAM OF THE CIRCUIT Sorry.. i had no perfboards left :) had to build it on a piece of cardboard. When the person is telling the truth. When the person is telling a lie.