Capacitance

Capacitance is a measure of the quantity of electric charge stored for a given electric potential. The most general form of charge storage device is a two-plate capacitor. If the charges on the plates are +Q and -Q, and V gives the voltage difference between the plates, then the capacitance is given by c=Q/v. The capacitance of the majority of capacitors used in electronic circuits is several orders of size smaller than the farad. The most ordinary units of capacitance in use today are the millifarad (mF), microfarad (µF), the nanofarad (nF) and the picofarad (pF).
The dielectric constant for a number of very useful dielectrics changes as a function of the applied electrical field, e.g. ferroelectric materials, so the capacitance for these devices is no longer purely a purpose of device geometry. If a capacitor is driven with a sinusoidal voltage, the dielectric constant, or more exactly referred to as the dielectric permittivity, is a function of frequency. A changing dielectric constant with frequency is referred to as a dielectric dispersion, and is governed by dielectric recreation processes, such as Debye relaxation.

River

A river is a natural waterway that transits water through a setting from higher to lower elevations. A river may have its basis in a spring, lake, from damp, boggy landscapes where the soil is waterlogged, from glacial melt, or from surface runoff of precipitation. Almost each and every one river is joined by other rivers and streams termed tributaries the highest of which are known as headwaters. Water may also begin from groundwater sources. Throughout the course of the river, the total volume transported downstream will often be a combination of the free water flow together with a important contribution flowing through sub-surface rocks and gravels that underlie the river and its floodplain. For many rivers in large valleys, this unseen component of flow may greatly go above the visible flow.
From their source, all rivers flow downhill, typically terminating in the sea or in a lake, through a confluence. In arid areas rivers sometimes end by losing water to desertion. River water may also infiltrate into the soil or pervious rock, where it becomes groundwater. Excessive abstraction of water for use in commerce, irrigation, etc., can also cause a river to dry before success its natural terminus.