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The Earth phase, Terra phase, terrestrial phase, or phase of Earth, is the shape of the directly sunlit portion of Earth as viewed from the Moon (or elsewhere extraterrestrially). From the Moon, Earth phases gradually and cyclically change over the period of a synodic month (about 29.53 days), as the orbital positions of the Moon around Earth ...
The term phase is sometimes used as a synonym for state of matter, but it is possible for a single compound to form different phases that are in the same state of matter. For example, ice is the solid state of water, but there are multiple phases of ice with different crystal structures , which are formed at different pressures and temperatures.
In a polyphase AC system, the instantaneous vector sum of the phases is zero. This neutral point is commonly used to refer the phase voltages to earth ground instead of connecting one of the phase conductors to earth. Any Δ-Y (delta-wye) connected transformer may be used for the purpose.
According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time. [6] Thus, since 1918, theorists have understood that the law of conservation of energy is the direct mathematical consequence of the translational symmetry of the quantity conjugate to energy, namely time.
The Earth's magnetic field protects the Earth from the deadly solar wind and has long been used for navigation. It originates in the fluid motions of the outer core. [24] The magnetic field in the upper atmosphere gives rise to the auroras. [26] Earth's dipole axis (pink line) is tilted away from the rotational axis (blue line).
In physics, matter is sometimes equated with particles that exhibit rest mass (i.e., that cannot travel at the speed of light), such as quarks and leptons. However, in both physics and chemistry, matter exhibits both wave-like and particle-like properties (the so-called wave–particle duality). [9] [10] [11]
The neutral conductor of a 3-phase, 4-wire system and the middle conductor of a 2- phase, 3-wire system must have at least 2 separate and distinct earth connections with a minimum of 2 different earth electrodes to have a satisfactory earth resistance; The earth electrodes must be interconnected to reduce earth resistance
In the physical sciences, a phase is a region of material that is chemically uniform, physically distinct, and (often) mechanically separable. In a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air is a third phase over the ice and water.