Question

Draw and explain temperature dependence of relation of thermal and electrical conductivity for real metals

Answer #1

In metals when temperature increases it leads to the increase in the vibration of the electrons in the lattice. It causes restriction to the motion of electrons as the number of collision increases ie drift velocity decreases. resistance is inversely proportional to drift velocity so decrease in drift velocity leads to increase in resistance (in fact resistivity because there is no change in dimension of the sample ie length and cross section) so it becomes difficult for the current to pass through it.

So increase in temperature results in decrease in electrical conductivity.

Electrical conductivity vs temperature graph is given below.

Thermal conductivity is a constant for a material. It is different for different material.

To determine the effect of the temperature dependence of the
thermal conductivity on the temperature distribution in a solid,
consider a material for which this dependence may be represented
by: k = k0 + a T, where “k0“ is a positive constant and “a” is a
coefficient that may be positive or negative. Starting with a
steady-state energy balance, derive a relationship for temperature
(T) as a function of distance (x) from the lower temperature wall.
You may assume that...

Describe the difference of temperature dependence in the
electrical conduction of intrinsic semiconductors and
metals/alloys; and
b) Explain the origins of different temperature dependent
electrical conduction behavior in extrinsic and intrinsic
semiconductors at intermediate temperature? However, at high and
low temperature regions why extrinsic semiconductors seem to
exhibit similar electrical conduction behaviors as the intrinsic
counterparts? Use sketches and/or equations if necessary.

Estimate the temperature (in Kelvins) at which GaAs has an
electrical conductivity of 4.0 x 10-3
(?-m)-1, assuming a temperature dependence for ? as
shown in Eq. 18.36. For GaAs, use a band gap of 1.42 eV, and a room
temperature (298K) conductivity of 1.0 x 10-6
(?-m)-1.

why thermal conductivity decreases when the temperature
difference increases

Explain thermal conductivity and R-Value of insulation
materials.

Metals are good thermal conductors — that is, when there is a
temperature difference across their ends, they transfer energy very
efficiently from the higher temperature end to the lower
temperature end. Based on this, would you expect a
thermal conductor generally to have a low specific heat capacity
(closer to sand) or a high specific heat capacity (closer to
water)?
A.
Low specific heat capacity
B.
High specific heat capacity

Give 3 application of thermal conductivity and explain in details
nicely

5-
The heat rate (Q) transferred through a metal rod depends on the
thermal conductivity (K) of the metal, the cross-sectional area of
the rod (A) and the temperature gradient (Y) across the rod. Find
the relation by the use of the dimensional analysis taking the
units of (K) (W/mK).

Derive/explain the how thermal conductivity can be
explained in terms of the kinetic theory of gasses.

Explain in detail how the microorganisms are classified based on
their temperature dependence

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