A
long tungsten heater wire is rated at
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Solution: Click For PDF Version
We will
workout the heat flow in the radial direction across the surface of
a ceramic cylinder of length,
The tungsten
wire is being heated at its rated power,
Temperature
of the wire is
Temperature
of the surface of the ceramic cylinder is
At thermal
equilibrium a radial temperature gradient will be established. Let
us call it
At thermal
equilibrium the rate of flow of heat across a cylindrical surface of
length 1 m at radial distance r from the axis will be
Let the thermal conductivity of the ceramic be k. According to the law of thermal conduction
Integrating the above expression, we get
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and is 0.520 mm in
diameter. It is embedded across the axis of a ceramic cylinder of
diameter 12.4 cm. When
operated at the rated power, the wire is at
,
the outside of the cylinder is at
.
We have to calculate the thermal conductivity of the ceramic.
,
and of diameter
.
It is given that the diameter of the tungsten wire fixed lengthwise
at the axis of the ceramic cylinder is
.
.
.
.
.
