Richardson's handbook of projection (1930)

1020 HANDBOOK OF PROJECTION FOR the insulating material by means of a wire, the condenser will "discharge" itself and return instantly to its former uncharged condition. Understand, when we disconnect our condenser from the power supply we do not release the strain. There still remains the "charge" in its plates which corresponds to the pull upon the rubber band, and unless the plates be shorted, that charge and strain will remain an appreciable time, in some types and sizes of condensers several minutes; in others a much less time. The charge will, however, gradually leak away whether or no the plates be shorted. If the condenser be large enough and be charged with say 100 or more volts, there will be a visible spark when the plates are shorted. RETAINS CHARGE.— I repeat : a condenser will retain its charge, unless the charge be in some manner used up or the plates be shorted, for a length of time depending upon the size and character of the condenser. It will vary from less than a minute to several minutes. The leakage away is gradual, CAPACITY. — Just as the amount of stretching of a rubber band is proportional to the force applied, so the charge produced or set up in a condenser is exactly proportional to the electrical pressure (voltage) applied. What is termed the "capacity" of a condenser is the amount of charge it will store for each volt applied, just as the elastic strength of a rubber band may be expressed as or in the number of inches it will stretch per pound of force applied. If we stretch the rubber too far it will break. If we apply too much pressure (voltage) to a condenser its