(See related pages)
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| Electric current | the time rate passage of charge through material; electric current i is the number of coulombs per second that passes a point in a material. The SI unit for electric current is the ampere (1 A = 1 C/s). (See page(s) 785; Sec. 13.1) |
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| Electrical resistance R | the measure of the difficulty of electric current's passage through a volume of material. Resistance increases with the length and increases with decreasing cross-sectional area of the material through which the current passes. SI unit: ohm (Ω). (See page(s) 785; Sec. 13.1) |
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| Electrical resistivity | a measure of the difficulty of electric current's passage through a unit volume of material. For a volume of material, ρe = RA/ l , where R = resistance of material, Ωl = its length, m; A = its cross-sectional area, m2. In SI units, ρe = ohm-meters (Ω· m) (See page(s) 785; Sec. 13.1) |
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| Electrical conductivity | a measure of the ease with which electric current passes through a unit volume of material. Units: (Ω· m)-1 . σe is the inverse of ρe . (See page(s) 785; Sec. 13.1) |
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| Electrical conductor | a material with a high electrical conductivity. Silver is a good conductor and has a σe = 6.3 × 107 (Ω · m)-1 . (See page(s) 785; Sec. 13.1) |
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| Electrical insulator | a material with a low electrical conductivity. Polyethylene is a poor conductor and has a σe = 10-15 to 10-17 (Ω · m)-1 . (See page(s) 785; Sec. 13.1) |
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| Semiconductor | a material whose electrical conductivity is approximately midway between the values for good conductors and insulators. For example, pure silicon is a semiconducting element and has σe = 4.3 × 10-4 (Ω · m)-1 at 300 K. (See page(s) 785; Sec. 13.1) |
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| Electric current density J | the electric current per unit area. SI units: amperes/meter2 (A/m2 ). (See page(s) 785; Sec. 13.1) |
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| Energy-band model | in this model the energies of the bonding valence electrons of the atoms of a solid form a band of energies. For example, the 3s valence electrons in a piece of sodium form a 3s energy band. Since there is only one 3s electron (the 3s orbital can contain two electrons), the 3s energy band in sodium metal is half-filled. (See page(s) 785; Sec. 13.2) |
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| Valence band | the energy band containing the valence electrons. In a conductor the valence band is also the conduction band. The valence band in a conducting metal is not full, and so some electrons can be energized to levels within the valence band and become conductive electrons. (See page(s) 785; Sec. 13.2) |
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| Conduction band | the unfilled energy levels into which electrons can be excited to become conductive electrons. In semiconductors and insulators there is an energy gap between the filled lower valence band and the upper empty conduction band. (See page(s) 785; Sec. 13.2) |
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| Intrinsic semiconductor | a semiconducting material that is essentially pure and for which the energy gap is small enough (about 1 eV) to be surmounted by thermal excitation; current carriers are electrons in the conduction band and holes in the valence band. (See page(s) 785; Sec. 13.3) |
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| Electron | a negative charge carrier with a charge of 1.60 × 10-19 C. (See page(s) 785; Sec. 13.3) |
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| Hole | a positive charge carrier with a charge of 1.60 × 10-19 C. (See page(s) 785; Sec. 13.3) |
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| n-type extrinsic semiconductor | a semiconducting material that has been doped with an n-type element (e.g., silicon doped with phosphorus). The n-type impurities donate electrons that have energies close to the conduction band. (See page(s) 785; Sec. 13.4) |
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| Donor levels | in the band theory, local energy levels near the conduction band. (See page(s) 786; Sec. 13.4) |
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| p-type extrinsic semiconductor | a semiconducting material that has been doped with a p-type element (e.g., silicon doped with aluminum). The p-type impurities provide electron holes close to the upper energy level of the valence band. (See page(s) 786; Sec. 13.4) |
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| Acceptor levels | in the band theory, local energy levels close to the valence band. (See page(s) 786; Sec. 13.4) |
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| Majority carriers | the type of charge carrier most prevalent in a semiconductor; the majority carriers in an n-type semiconductor are conduction electrons, and in a p-type semiconductor they are conduction holes. (See page(s) 786; Sec. 13.4) |
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| Minority carriers | the type of charge carrier in the lowest concentration in a semiconductor. The minority carriers in n-type semiconductors are holes, and in p-type semiconductors they are electrons. (See page(s) 786; Sec. 13.4) |
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| pn junction | an abrupt junction or boundary between p- and n-type regions within a single crystal of a semiconducting material. (See page(s) 786; Sec. 13.5) |
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| Bias | voltage applied to two electrodes of an electronic device. (See page(s) 786; Sec. 13.5) |
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| Forward bias | bias applied to a pn junction in the conducting direction; in a pn junction under forward bias, majority-carrier electrons and holes flow toward the junction so that a large current flows. (See page(s) 786; Sec. 13.5) |
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| Reverse bias | bias applied to a pn junction so that little current flows; in a pn junction under reverse bias, majority-carrier electrons and holes flow away from the junction. (See page(s) 786; Sec. 13.5) |
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| Rectifier diode | a pn junction diode that converts alternating current to direct current (AC to DC). (See page(s) 786; Sec. 13.5) |
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| Bipolar transistor | a three-element, two-junction semiconducting device. The three basic elements of the transistor are the emitter, base, and collector. Bipolar junction transistors (BJTs) can be of the npn or pnp types. The emitter-base junction is and the collector-base junction reverse-biased so that the transistor can act as a current amplification device. (See page(s) 786; Sec. 13.5) |