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| Phillips screw
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Screw in which crossed slots are recessed into the head. It is easier and faster to use than a single slotted screw because the slots do not reach the edges of the head, making the screwdriver automatically centered and giving it less tendency to slip from the head. |
| Phillips screwdriver
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The phillips screwdriver is a common screwdriver used in electrical, wood and general applications. |
| Phosphor
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An inorganic chemical compound processed into a powder and deposited on the inner glass surface of fluorescent tubes and some mercury and metal halide lamp bulbs. Phosphors are designed to absorb short wavelength ultraviolet radiation and to transform and emit it as visible light. |
| Photo-oxidation
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Oxidation caused by rays of the sun. |
| Photobiological hydrogen production
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A hydrogen production process that process uses algae. Under certain conditions, the pigments in certain types of algae absorb solar energy. An enzyme in the cell acts as a catalyst to split water molecules. Some of the bacteria produces hydrogen after they grow on a substrate. |
| Photocurrent
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An electric current induced by radiant energy. |
| Photoelectric cell
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A device for measuring light intensity that works by converting light falling on, or reach it, to electricity, and then measuring the current; used in photometers. |
| Photoelectric switch
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Switches, used mainly for situations such as sentry devices or outside lights. The generation of electricity by the photovoltaic cell when light is present. |
| Photoelectrochemical cell
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A type of photovoltaic device in which the electricity induced in the cell is used immediately within the cell to produce a chemical, such as hydrogen, which can then be withdrawn for use. |
| Photoelectrolysis hydrogen production
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The production of hydrogen using a photoelectrochemical cell. |
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