5A40.20 - Charge Propelled Cylinder
Demonstrate electrostatic induction of a neutral object with an aluminum can and a charged rod.
Pull out a soda can with no dents in it. Pull out a teflon rod with fur. If requested, pull out a nylon rod with silk to show induction happens with both positively and negatively charged objects.
Lay soda can on its side so it is able to roll. Then vigorously rub the fur on the teflon rod until you start to hear snipping noises. Bring rod up parallel to the can and watch the can attract towards the rod. If requested, you can then vigorously charge the nylon rod with the silk (no noises to let you know it is charged). Bring rod up parallel to the can and watch the can attract towards the nylon rod as well.
Electrostatic induction is a redistribution of electrical charge in an object, caused by the influence of nearby charges, due to Coulomb's law. When a charged rod is brought in the vacinity of the neutral soda can, the internal charge of the soda can will separate. The soda can will have no net electric charge, but these induced surface charges create an opposing electric field that exactly cancels the field of the external charge throughout the interior of the metal.
The positive charge forms nearest to the negatively charged teflon rod, while the negative charge moves to the far side of the can. If the rod is close enough, the attraction between the negative charge on the rod and the positive charge on the can will cause the can to then begin to rotate towards the rod. In the end, the soda can will have no net electric charge, but by electrostatic induction a separation of charge can occur causing the can to appear to have a positive charge on it when the negatively charged teflon rod is in the vicinity. Opposite for the presence of the positively charged nylon rod.