Name: Superconductivity: An Overview
Uploaded: 2019-07-19
Duration: 2 min 51 s
Description: Resistance of mercury at very low temperatures reduces to nearly zero. Certain materials exhibit this property of superconductivity. Let's learn more.

Question

Define the terms resistivity and conductivity and state their SI units. Draw a graph showing the variation of resistivity with temperature for a typical semiconductor.

Accepted Answer

The resistivity is given by: $ρ = \frac{m}{{ne}^{2} τ}$

where
$n =$ Number density of electrons
$τ =$ Relaxation time

With the rise in temperature, the number density of electrons and holes (in case of semiconductors) increases, where $τ$ remains constant. So, $ρ$ (resistivity) decreases with increase in temperature.

From the above, we can infer that $ρ \propto \frac{1}{T}$

Thus it is of the form $y = \frac{k}{x}$

The graph of it is a hyperbolic curve.Also resistivity and temperature also cannot be equal to zero or negative. Hence we get the curve only in the first quadrant.

This the required graph of the question.

Resistivity is a property of the material. It changes with the material and temperature. It is the electrical resistance of a conductor of unit cross-sectional area and unit length.
Semiconductors are materials which have a conductivity between conductors (generally metals) and nonconductors or insulators (such as most ceramics). Semiconductors can be pure elements, such as silicon or germanium, or compounds such as gallium arsenide or cadmium selenide. The resistivity of a semiconductor decreases with temperature.

Define the terms resistivity and conductivity and state their SI units. Draw a graph showing the variation of resistivity with temperature for a typical semiconductor.

Important Questions on Current Electricity

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