Page 95 - The Illustrated Dictionary of Electronics

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80 BNC • Boltzmann’s principle

operation of the internal heater element (if the
thermistor has one).
bof Abbreviation of barium oxide ferrite.
boffle A loudspeaker enclosure consisting of
stretched screens that are sound absorbing and
elastic.
BNC bogie Also called bogey. 1. The exact value of a
specified characteristic. Thus, if resistance is
given as 1 kΩ ±0.5%, the bogie value is 1 kΩ. 2.
nected and disconnected. It is commonly used The average value (i.e., the ARITHMETIC MEAN).
with test equipment. 3. A false or unidentified echo on a radar screen.
B-negative Alternative expression for B-MINUS. Bohr atom The concept of the nature of the atom,
BNL Abbreviation of Brookhaven National proposed by Niels Bohr in 1913 partly to explain
Laboratory. why the electrons in the Rutherford atom do not
BO Abbreviation of beat oscillator. Also abbreviated fly off into space or fall into the nucleus. The Bohr
BFO. theory places the electrons in permissible orbits
board 1. A panel containing patch jacks. 2. A where they cannot radiate energy (see BOHR RA-
printed circuit. DIUS). They can radiate or absorb energy, how-
boat A type of crucible in which a semiconductor ever, if they go to a lower orbit or to a higher orbit,
material is melted and sometimes processed. The respectively. Compare RUTHERFORD ATOM.
material of which the boat is made (e.g., graphite) bohrium Symbol, Bh. Also called unnilseptium
does not react with or contaminate the semicon- (Uns). Atomic number, 107. The most common
ductor material. isotope has atomic weight 262. Classified as a
bobbin 1. A usually nonmetallic spool on which a transition metal. It is human-made and is not
coil is wound. 2. The form onto which the voice known to occur in nature.
coil of a loudspeaker is wound. Bohr radius Symbol, a 0. A physical constant
Bode plot A pair of curves plotted to the same fre- whose value is approximately 5.291772 × 10 –11
quency axis, one showing the gain of a network or meter.
amplifier and the other showing its phase shift. boiling point Abbreviation, bp. The temperature at
Phase and amplitude of active and passive net- which a liquid vaporizes. The boiling point of wa-
works can be exhibited. Also called Bode curve ter in air at a pressure of one atmosphere is
and Bode diagram. 100°C or 212°F.
body-antenna effect The tendency of the human bolometer Any device that is essentially a small,
body to act as a receiving antenna when a finger nonrectifying, temperature-sensitive resistor that
is touched to the antenna input terminal of a re- can be used for heat sensing, radio-frequency
ceiver or when a hand (or the whole body) is power measurement, curve changing, demodula-
brought close enough to the circuit to provide ca- tion, circuit protection, etc. Included in this cate-
pacitive coupling. gory are the BARRETTER, the THERMISTOR, and
body capacitance Capacitance between the body the wire-type FUSE.
of the operator (as one plate of an equivalent ca- bolometer bridge A dc bridge in which a bolometer
pacitor) and a piece of electronic equipment (as is one of the four arms. The bridge is balanced
the other plate). This phantom capacitance is of- first with the bolometer cold. The bolometer then
ten the cause of detuning and of the injection of is excited with a radio-frequency (RF) current,
interfering signals and noise because the body whereupon the resultant heating changes the
acts as a pickup antenna. bolometer resistance. The bridge is rebalanced for
body electrode 1. An electrode attached to the the new resistance. The RF power driving the
human body (or to the body of a laboratory ani- bolometer is determined according to a predeter-
mal) to conduct body-generated currents to an mined function of bridge settings versus RF input
instrument, as in cardiography, electroenceph- power.
alography, and myography. 2. An electrode at- Boltzmann constant Symbol, k. A figure that en-
tached to the human body (or to the body of a ters into the calculation of thermionic emission
laboratory animal) to conduct currents into the and of thermal noise factor. It represents the tem-
body, as in shock therapy and skin-resistance perature equivalent of work function, in electron
measurement. volts per Kelvin (eV/K) or joules per Kelvin (J/K).
body leakage Leakage of current through the bulk The values are approximately:
or body of a dielectric material, as opposed to –5 –23
SURFACE LEAKAGE. k = 8.617 × 10 eV/K = 1.38 × 10 J/K
body temperature In a thermistor, a rating that Boltzmann’s principle A description of the statis-
represents the temperature measured on the tical distribution of large numbers of tiny parti-
surface of the device. It is any combination of cles under the influence of a force, such as an
ambient temperature, power dissipation, and electric or magnetic field. When the system is in