Electroscopes: how to find an electric charge
How can you make a DIY electric charge determinant?
Warning! Only under adult supervision.
- rubber lid;
- 2 paper clips;
- 2 pieces of foil;
Make two holes in a rubber lid equal distances from the center. Put an unfolded paper clip through each hole. Hang identical pieces of foil on the paper clips and put the setup on a glass. Rub a balloon and some styrofoam together. First, hold each item to the lid separately – the pieces of foil should repel one another. Hold the items to the lid together – the foil pieces should attract each other.
The friction of two objects against each other causes the transfer of electrons from one object to the other. When this happens, the object that gives electrons gains a positive charge, and the object that accepts electrons gains a negative charge. When the balloon and the styrofoam are rubbed against each other, their surfaces gain opposite charges: the balloon becomes positive, and the styrofoam becomes negative. You can prove the presence of a charge on the surface of each object using a simple device – a DIY electroscope. If you bring a charged object to the electrodes (the paper clips), this causes a redistribution of charges in the conducting clip-foil system. As a result, the paper clips and foil receive induced charges. When one charged object is held close to the paper clips, the pieces of foil acquire the same charge and repel each other. When oppositely-charged objects are held close to the paper clips, the pieces of foil will attract each other. When they touch, the pieces of foil exchange charges and their charges eventually equalize. At this point, they simply stop attracting one another.
Cool experiments are waiting for you in the MEL Chemistry subscription!