Do all bodies conduct or allow electricity to pass through them equally well?
Although there is no substance that can entirely prevent the passage of electricity, nor any that does not oppose some resistance to its passage, yet it moves with a much greater facility through a certain class of substances than through others. Those substances which facilitate its passage are called conductors; those that retard or almost prevent it, are called non-conductors.
What substances are good conductors of electricity?
The metals, charcoal, the earth, water, and most fluids, except oils, the human body, etc., are good conductors.
What substances obstruct the passage of electricity, or are “non-conductors”?
Glass, resin, oil, silk, sulphur, dry air, etc., etc., are non-conductors.
What is an electrical machine?
An electrical machine is an arrangement by which quantities of electricity can be collected and discharged.
One type of the electrical machine most usually employed consists of a large circular plate of glass, mounted upon a metallic axis, and supported upon pillars fixed to a secure base, so that the plate can, by means of a handle, be turned with ease. Upon the supports of the glass, and fixed so as to press easily but uniformly on the plate, are four rubbers; and flaps of silk, oiled on one side, are attached to these, and secured to fixed supports by several silk cords. When the machine is put in motion, these flaps of silk are drawn tightly against the glass, and thus the friction is increased, and electricity excited.
Do we know what electricity is?