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Ammeter—an instrument for measuring electric current in amperes.

ATP (adenosine triphosphate)—a large biomolecule, C10H16N5O13P3, which contains high-energy bonds. ATP is used to transport energy to cells for use in biochemical processes, including muscle contraction and enzymatic metabolism.

Autotroph—an organism capable of synthesizing its own food from inorganic substances, using light or chemical energy. Green plants, algae, and certain bacteria are autotrophs

Biomass—the total quantity or weight of organisms in a given area or volume.

Capillary action (or capillarity)— the ability of intermolecular forces (through adhesion and cohesion) to draw liquid along a narrow tube or groove, even against other forces such as gravity. In porous materials, like paper and sponges, the small, interconnected pores act as narrow tubes, allowing capillary forces to pull liquid into the material.

Carnivores—an animal that feeds on flesh.

Conduction band—an energy band partially filled with electrons in a crystalline solid. Electrons within the conduction band are not bound to a specific atom, making them mobile charge carriers in solids. These free electrons are responsible for the conduction of electrical currents in metals and other electrical conductors.

Doping—the intentional introduction of chemical elements with which one can obtain a surplus of either positive charge carriers (p-conducting semiconductor layer) or negative charge carriers (n-conducting semiconductor layer) from the semiconductor material.

Electrode—1) a solid electric conductor through which an electric current enters or leaves an electrolytic cell or other medium. 2) a collector or emitter of electric charge or of electric-charge carriers, as in a semiconducting device

Electrolyte—A chemical compound that ionizes when dissolved or molten to produce an electrically conductive medium.

Electromagnetic wave (or electromagnetic raidation)—sinusoidal propagation of related electric and magnetic fields. Being sinusoidal, any electromagnetic wave can be characterized by its frequency or wavelength. Scientists have divided the continuous possible range of frequencies into categories based on the different ways that the waves interact with matter. These categories are radio waves, microwaves, infrared radiation, light, ultraviolet radiation, X rays, and gamma rays.

Electromotive force (emf)—the voltage generated by a source such as a battery or a solar cell. The emf is not actually a force and is measured in units of voltage. The emf is different from the potential difference between the terminals of a power source.

Electron hole—(physics) a vacant position in a crystal left by the absence of an electron, especially a position in a semiconductor that acts as a carrier of positive electric charge.

Electron-hole pair—when an electron in a solid transitions from the valence band to the conduction band, its atom is left with a vacancy, or hole. This hole and electron form a pair of charge carriers in the solid with equal but opposite charges. An electron may also recombine with a hole, releasing energy and neutralizing the electrical charges.

Geothermal—of, relating to, or produced by the internal heat of the earth: "some 70% of Iceland's energy needs are met from geothermal sources."

Glucose—a simple sugar, C6H12O6, that is the main byproduct of the photosynthesis reaction and an important energy source in living organisms. It is a component of many carbohydrates.

Impedance (electrical)—a measure of the overall opposition to the flow of current in an electric circuit, in other words, how much the circuit impedes the flow of circuit. It is like resistance, but it also takes into account the effects of capacitance and inductance. In simple circuits which have no capacitance or inductance, there is no distinction between impedance and resistance.

Impedance matching—a technique of electric circuit design in which one component provides power to another, and the output circuit of the first component has the same impedance as the input circuit of the second component. Maximum power transfer is achieved when the impedances in both circuits are exactly the same.

Internal resistance—(physics)  the resistance of a power cell, accumulator, etc., usually given as (E-V)/I, where E is the electromotive force of the power cell, and V the potential difference between terminals when it is delivering a current, I.

Monocrystalline—a single crystal solid in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries.

NADPH—the reduced (extra electron) form of nicotinamide adenine dinucleotide phosphate (NADP) that serves as an electron carrier in biosynthetic reactions including photosynthesis.

Nanoparticle—an object which has at least one dimension so small that it is most conveniently measured in nanometers (The defined size sometimes is restricted to the range: 1–100 nm.)

Nanotechnology—technology development whose unifying theme is the control of matter on the atomic, molecular, or macromolecular scale, approximately 1-100 nanometers, to create and use structures, devices, and systems that have novel properties.

Nonpolar—(physics) not containing a dipole, with equal sharing of the bond of electrons; lacking a permanently dipolar molecule. (chemistry) pertaining to a compound that is nonionic or does not dissociate into ions. Examples of nonpolar compounds are fats and oil. Many nonpolar compounds are hydrophobic. They do not readily dissolve in water but they do in a nonpolar solvent or environment.

Omnivores—an animal or person that eats food of both plant and animal origin.

Open-circuit volatge—open-circuit voltage (abbreviated as OCV or VOC ) is the difference of electrical potential between two terminals of a device when there is no external load connected, i.e. the circuit is broken or open. Under these conditions there is no external electric current between the terminals, even though there may be current internally.

Organelle—A differentiated structure within a cell, such as a mitochondrion, vacuole, or chloroplast, that performs a specific function.

Oxidation-reduction reaction (also redox reaction)—a chemical reaction involving the transfer of electrons from one reactant to another or the sharing of electrons between reactions. Oxidation is the process through which a reactant loses an electron (ionic bond) or the loss of a shared electron (covalent bond); reduction is the process through which a reactant gains an electron. Oxidation and reduction generally occur together as two halves of a single reaction, usually one that releases energy.

Photoelectron—an electron emitted from an atom or molecule by interaction with a photon, esp. an electron emitted from a solid surface by the action of light.

Polar—having a pair of equal and opposite charges. A polar molecule forms when an atom of high electronegativity (one that attracts electrons), such as chlorine, bonds with a less electronegative atom such as hydrogen. Because the more electronegative atom pulls the electron(s) away from the other atom, the molecule formed has one end which is negatively charged and another which is positively charged. Polar molecules tend to align themselves because the negative end of each molecule is attracted to the positive end of other molecules, and vice versa. Water is a well-known example of a polar molecule.

Polycrystalline—polycrystalline materials are solids that are composed of many crystallites of varying size and orientation. The variation in direction can be random (called random texture) or directed, possibly due to growth and processing conditions. Polycrystalline solar cells are made out of many small individual crystals, and examined closely at the reflection of the sunlight one can actually see the crystal matrices themselves, which look almost like a mosaic relief in the panel. These panels therefore look different from the monocrystalline type that consists of large singular crystals. These look smoother and darker in their finish and don't have that "shattered mosaic look."

Polymer—a large molecule with a linear primary structure consisting of repeating units that are small molecules connected by covalent bonds.

Prototype—the first or original model of a product, which is built to experiment with the function and feel of the new design and to see if changes to the design is necessary prior to constructing the final product. In many fields, “rapid-prototyping” techniques are used to implement part, but not all, of the complete design. This allows designers and manufacturers to rapidly and inexpensively experiment with parts of the design that are most likely to have problems, solve those problems, and then build the full design.

Protrusion—extension beyond the usual limits, or above a plane surface.

Quartzite—an extremely compact, hard, granular rock consisting essentially of quartz (SiO2). It often occurs as silicified sandstone.

Recombination (Light)—when a free electron combines with an electron hole. Electron-hole recombination is called radiative if the released energy is light or other electromagnetic radiation and nonradiative if the energy is released as heat.

Respiration—the oxidative process occurring within living cells by which the chemical energy of organic molecules is released in a series of metabolic steps involving the consumption of oxygen and the liberation of carbon dioxide and water.

Semiconductor—a solid substance, usually crystalline, that has a conductivity between that of an insulator and that of most metals. The specific electrical properties depend on the temperature of the semiconductor and can be altered by adding impurities to the crystal.

Short-circuit current—the short-circuit current is the current through a power cell when the voltage across the cell is zero (i.e., when the cell is short-circuited). In a solar cell, the short-circuit current is due to the generation and collection of light-generated carriers. For an ideal solar cell with moderate resistive loss, the short-circuit current and the light-generated current are identical. In this case, the short-circuit current is the largest current which may be drawn from the solar cell.

Slurry—a fluid mixture of solid particles suspended in a liquid.

Stratum—a thin layer within any structure: "thin strata of air."

Solar cell—(also photovoltaic cell) a device that transforms light energy of photons into electrical energy of moving charges, typically consisting of layers or sheets of specially prepared silicon. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell is used when the light source is unspecified. Solar cells are used as power supplies in calculators, satellities, and other devices, and as a primary source of electricity in remote locations.

Solar spectrum—the total distribution of electromagnetic radiation emanating from the sun. The different regions of the solar spectrum are described by their wavelength range. The visible region extends from about 390 to 780 nanometers

Stoma—any of the minute pores in the epidermis of the leaf or stem of a plant, forming a slit of variable width that allows movement of gases in and out of the intercellular spaces

Thylakoid—each of a number of flattened sacs inside a chloroplast, bounded by pigmented membranes on which the light reactions of photosynthesis take place. Thylakoids are arranged in stacks.

Valence band—an energy band in a solid, corresponding to the highest range of energies an electron can have while still being bound to a specific atom. Electrons with energies higher than the valence band are in the conduction band and are free to move throughout the material.

Valence electron—(chemistry) an electron in the outer shell or energy orbital of an atom, which is responsible for the atom's chemical and electrical properties; (physics) the highest energy electrons that are still bound to specific atoms. Electrons that are no longer bound to atoms are called conduction electrons.

Visible spectrum—the portion of the electromagnetic spectrum that can be seen with the human eye, often divided into colors: red, orange, yellow, green, blue, violet. The wavelength range for the visible spectrum is approximately 380nm (violet light) to 750nm (red light).

Voltage (also electrical potential difference)—the difference in electric potential between two points or the difference in electric potential energy per unit charge between two points. A voltage may represent either a source of energy (electromotive force as in a battery), or it may represent lost or stored energy (potential drop).

Wavelength—distance between repeating parts of a wave (e.g., crest to crest or trough to trough). Wavelength is inversely proportional to frequency: λ = v/f, where λ is wavelength, v is wave speed, and f is frequency.

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