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British
Thermal Unit(BTU)
It
is a standard unit of energy that is used in the United States and sometimes in
UK. It represents the amount of thermal energy necessary to raise the
temperature of one pound of pure water by one Fahrenheit from the temperature
at which water has its greatest density i.e. 39 oF. The Btu is a
measure in so called English system of units.
1Btu = 1055 Joules, a unit of energy in SI
units.
Brittle
Substances
Substances which
break as soon as the stress is increased beyond elastic limit are called
brittle substances.
Bronze
A
copper rich copper tin alloy.
Brownian
Motion
Irregular, random
and zigzag motion of suspended particles in liquid is called Brownian motion.
Bubble
Chamber
It
was designed by D M Glaser in 1952. It is device used to detect ionizing
radiation. The principle underlying this chamber is as follows:
The
chamber uses super heated liquid (a liquid that has been heated above its
normal boiling point by increasing the pressure over it. When the pressure is
suddenly reduced to atmospheric pressure, the liquid remains in unstable super
heated state for some time. If during
this interval, an ionizing particle traverses the liquid within few milli
seconds after the pressure is released, ions are formed which act as centers
for formation of vapor bubbles. The vapor bubbles grow at rapid rate and attain
a visible size in a time of order of
10-100
μsec.
Bulk
Modulus
The ratio of bulk
stress to bulk strain within the elastic limit is called bulk modulus or
coefficient of volume elasticity.
Bulk
Stress
If a body is
subjected to the same force normal to all its faces such that there is a change
in its volume then normal force per unit area is called bulk stress.
Buoyancy
The property of
fluid as per which, a net upward force is exerted on the object by the fluid in
which object is immersed partially or completely.
Buoyant
Force
As per Archimedes
(a Greek mathematician), a body which is completely or partially immersed in a
fluid will experience an upward force called buoyant force, which is equal to
weight of fluid displaced by object. The buoyant force is due to difference
between the pressure at the bottom of the object pushing up on it, and the
pressure at the top pushing down.
Burgers
Vector
The magnitude and
direction of the lattice distortion associated with a dislocation is expressed
in terms of a vector called burger vector.
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