Advection fog shows up mostly in places where warm, tropical air meets cooler ocean water. When the moist, warm air makes contact with the cooler surface air, water vapor condenses to create fog. This process is called advection, a scientific name describing the movement of fluid. Advection fog forms when warm, moist air passes over a cool surface. Fog that is said to “burn off” in the morning sun is radiation fog. Ground fog does not reach as high as any of the clouds overhead. Sometimes people use the term “ ground fog” to refer to radiation fog. As heat is transferred from the ground to the air, water droplets form. Radiation fog forms in the evening when heat absorbed by the Earth’s surface during the day is radiated into the air. Types of Fog There are several different types of fog, including radiation fog, advection fog, valley fog, and freezing fog. Mist can reduce visibility to between one and two kilometers. Fog cuts visibility down to one kilometer, meaning it will prevent you from seeing further away than one kilometer from where you’re standing. There are more water molecules in the same amount of space in a fog. This means fog is more massive and thicker than mist. Depending on the humidity and temperature, fog can form very suddenly and then disappear just as quickly. Sea fog, which shows up near bodies of salty water, is formed as water vapor condenses around bits of salt. Water vapor con denses around these microscopic solid particles. In order for fog to form, dust or some kind of air pollution needs to be in the air. There has to be a lot of water vapor in the air for fog to form. You can see fog because of these tiny water droplets. During condensation, molecules of water vapor combine to make tiny liquid water droplets that hang in the air. Fog shows up when water vapor, or water in its gaseous form, condenses. Even monuments like London Bridge, in London, England, or the Golden Gate Bridge, in San Francisco, California, are almost impossible to see in thick fog. In some conditions, fog can be so thick that it makes it hard to drive safely because it obscures the road and other cars. Fog can be thin or thick, meaning people have difficulty seeing through it. More information can be found on UL 943, Standard for Ground-Fault Circuit Interrupters.Ī system intended to provide protection of equipment from damaging line-to-ground fault currents by operating to cause a disconnecting means to open all ungrounded conductors of the faulted circuit.Fog is a cloud that touches the ground. Ground-Fault Circuit Interrupter GFCI – Ground fault circuit interrupter (photo credit: )Ī device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds the values established for a Class A device.Ĭlass A ground-fault circuit interrupters trip when the current to ground has a value in the range of 4 mA to 6 mA. An unintentional, electrically conducting connection between an ungrounded conductor of an electrical circuit and the normally non-current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth.Īn electrically conductive path from the point of a ground fault on a wiring system through normally non–current-carrying conductors, equipment, or the earth to the electrical supply source.Īn intentionally constructed, permanent, low-impedance electrically conductive path designed and intended to carry current under ground-fault conditions from the point of a ground fault on a wiring system to the electrical supply source and that facilitates the operation of the overcurrent protective device or ground fault detectors on high-impedance grounded systems.ġ5.
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