Electricity may be said to have a finger in most pies. From its manifestations it would appear to be an all-pervading force, and modern research tends always to substantiate this conclusion. Thus two coins—a cent and a quarter—cannot be brought into contact without producing their quotum of electrical force, and in like manner the principles of its working may often be demonstrated by the simplest apparatus.
There are two states which this subtle force assumes, called Static and Dynamic. The former word indicates a condition of rest, and is applied to electricity when stored in suitable magazines ready for discharge at a favorable opportunity, just as water may be held in lofty reservoirs, ready to pour down and perform work—whether useful or otherwise—if the pipes be opened. Dynamic, on the other hand, indicates a state of motion; so that Dynamic Electricity means that it is flowing along conductors from one place, where there is a large quantity of the force, to another less powerful, in the same way as—again using the comparison with water—the latter pours along connecting pipes from a high level to a lower. Phenomena of static electricity are invariably produced by friction, and some experiments of this class will be first described.
The chief element of success in friction electrical experiments is a warm and dry atmosphere. The operations should therefore be conducted in a well-ventilated room where the fire has been burning some time, whilst all apparatus may with advantage have stood warming for some time before.
1. Rub a 6-inch square of brown paper with a warm silk handkerchief, then place flat against the wall or marble fireplace. It should cleave tightly to either of the latter surfaces.
2. Again electrify the brown paper and hold it above any willing person’s head of hair. The locks will fly up towards the paper and appear like bristles. You may then make sure of a safe retreat, and utter side remarks about “wire.”
3. Sprint smartly after the cat, which, like the other apparatus, should have been warming itself on the hearthrug, and having effected a capture, stroke the fur backwards. If the hand be not moist, considerable sparking should occur and be easily visible in a darkened room.
4. By combing dry hair quickly with a warm ebonite comb, and then applying this to the knuckles, distinct sparks may often be obtained.
5. Cut a piece of paper into small confetti, and place near it a stick of sealing-wax or ebonite rod, which has been rubbed with flannel. The paper atoms are attracted to the rod through a distance of one inch or more, and then, contact having once occurred, they immediately drop off.
6. In the previous experiment it was found that the paper atoms having once touched the rod, dropped off directly. This behavior was caused by a sequence of happenings.
First the negatively excited sealing-wax caused positive charges to possess the upper surface of the paper—the equal negative charges being driven downwards—so that, the two kinds of electric energy having a mutual affinity, the paper sprang towards the wax. Immediately they touched, however, the positive charges of the paper were neutralized by the large excess of negative energy from the sealing-wax, and then, since electricities of like sign exercise mutual repulsion, the negative paper was driven from the negative wax.