Discharge

Discharge, in Electricity, means the neutralisation of free electricity by a removal of the stress that has kept it in place. Thus a cloud of water particles in the air may be heavily charged with electricity, and may be prevented from discharging itself by' too great a thickness of air insulation between it and the earth or another cloud. This thickness of air is subjected to a stress, and may be insufficiently strong if the pressure or potential in the thunder-cloud becomes greater. This being the case a discharge takes place through the air to the earth or neighbouring cloud, and the tension is relieved. If a charged conductor be pointed, it will be found that the density of the electricity is much greater in the pointed regions, and that a silent convective discharge may take place there. [Brush Discharge.] In Hydraulics the discharge of ariver, weir, or other channel for the flow of water denotes the quantity of water that passes over in a given time. It will depend on the head of water and on the dimensions of the channel. The discharge may be estimated for small streams by triangular or rectangular gauge-notches (q.v.), through which the water is made to pass. In the case of large discharges, it is usual to calculate the quantity by means of observations on the average speed of flow and on the dimensions of the channel.