Current (fluid)
From Wikipedia, the free encyclopedia
A current is fluid flow, common examples are water or air. A current is any continuous, directed movement of a fluid. Naturally occurring currents can be explained as an increase in entropy.
In a river or stream, the water is influenced by gravity, and flows downhill to reduce its potential energy. The movement of water in a stream is called the current and this movement will vary from place to place and time to time dependent upon the volume of water, the slope, and the shape. In tidal zones, the current in rivers and streams may reverse on the flood tide before resuming on the ebb tide.
Air currents may be caused by differences in temperature, pressure, or impurity concentration. Temperature differences can cause air currents because warmer air is less dense than cooler air, causing the warmer air to appear "lighter." Thus, if the warm air is under the cool air, air currents will form as they exchange places. Pressure differences also cause air currents as the air flows from areas of higher pressure to areas of lower pressure. Impurities cause air currents due to entropy, which is the natural tendency of a system to move to a disordered state. For example, if perfume is sprayed in the corner of a closed room, it will eventually disperse evenly to the entire room.
