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bimetallic strip. A strip made of two different types of metal fastened together, side-by-side. When heated,
these two metals expand differently, causing the strip to warp, or bend.
Bimetallic strips are used in some types of thermometers and circuit breakers.
binary coded decimal. See BCD.
binary number system. The number system whose base is two. It uses only two values, zero and one.
Each position represents a value twice that of the position to its right. For example:
64 32 16 8 4 2 1
0 0 0 0 0 0 1 = 1
0 0 0 0 0 1 0 = 2
0 0 0 0 1 0 0 = 4
0 0 0 1 0 0 0 = 8
0 0 1 0 0 0 0 = 16
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 74
0 1 0 0 0 0 0 = 32
1 0 0 0 0 0 0 = 64
The binary number system is useful when working with digital electronics, because the two basic
conditions of electricity, on and off, can be used to represent the two bits of the binary number system.
When the system is on, the bit one is represented, and when it is off, zero is represented.
binding post (electrical equipment). A connector used to fasten a conductor to an electrical test panel.
Most binding posts have an insulated nut that can be turned with the fingers to grip the wire. Some binding
posts have, in addition to the nut, holes for a banana plug.
binoculars. A form of hand-held optical instrument used to observe distant objects. Binoculars have a set
of magnifying lenses for each eye, and prisms are used to get a high degree of magnification in a short
physical length.
binomial. An algebraic expression that contains two terms. 4X + 2Y is a binomial expression.
bioastronautics. The branch of science dealing with the medical and biological aspects of astronautics.
biochemistry. The branch of chemistry dealing with chemical compounds and processes involved with
living organisms.
biocidal action. The action of certain chemicals that kill bacteria. Biocidal agents are used in turbine
engine fuel to kill the bacteria and microbes living in water that condenses inside aircraft fuel tanks. If these
microscopic organisms are not killed, they will multiply and form a scum that holds water against the
aircraft skin and promotes corrosion.
Biocidal additives are also put in aircraft dope used on cotton or linen fabric to kill bacteria that
can destroy either of these organic fabrics.
biocidal agent. A chemical compound that is destructive to certain types of living organisms.
biodegradable. A condition of a material that allows it to be broken down into simple products by the
action of certain types of microorganisms.
Paper and wood are normally biodegradable. If they are buried, they will, in time, change into
simpler chemical compounds. Some man-made materials are not biodegradable, and they will not change.
Disposing of large volumes of nonbiodegradable materials can be an environmental problem.
biological warfare. Warfare using disease-producing microorganisms or toxic biological products to cause
death or injury to humans, animals, or plants.
biophysics. The branch of physics dealing with the application of physical laws to biological problems.
biplane. An airplane having two main supporting aerodynamic surfaces (wings). The wings of a biplane
are normally mounted so that one is approximately above the other.
bipolar transistor. A solid-state component in which the flow of current between its emitter and collector
is controlled by a much smaller flow of current into or out of its base. Bipolar transistors may be of either
the NPN or PNP type.
bipropellant rocket. A rocket using two separate propellants which are kept separate until they are mixed
in the combustion chamber.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 75
bisector of a line. A point on the line that divides it into two segments of equal length.
bisector of an angle. A line that divides an angle into two equal angles.
bismuth. A heavy metallic, pentavalent chemical element. Bismuth is brittle, grayish-white, crystalline,
and highly diamagnetic. Bismuth’s symbol is Bi, its atomic number is 83, and its atomic weight is 208.980.
Bismuth is often used to dope silicon or germanium to make P-type semiconductor material and is
also used as an alloying agent for changing the characteristic of certain metals.
bistable. A condition of a mechanical or electrical device in which either of two conditions may exist as a
steady state.
bistable circuit (electronic circuit). A circuit having two stable conditions. Either condition may be
chosen, and the circuit will operate in that condition until it is purposely changed. The circuit will not
change its condition by itself.
bistable multivibrator (electronic circuit). A type of oscillator using two transistors. Only one transistor
　
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