Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12
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In a Semiconductor, (A) There Are No Free Electrons at 0 K (B) There Are No Free Electrons at Any Temperature (C) the Number of Free Electrons Increases with Temperature - Physics

Short Note

In a semiconductor,
(a) there are no free electrons at 0 K
(b) there are no free electrons at any temperature
(c) the number of free electrons increases with temperature
(d) the number of free electrons is less than that in a conductor.

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Solution

(a) there are no free electrons at 0 K
(c) the number of free electrons increases with temperature
(d) the number of free electrons is less than that in a conductor

In semiconductors, the valence band is full at 0 K, but the conduction band is empty. So, no free electron is available for conduction at 0 K.
As the temperature increases, covalent bonds that provide free charge carriers for conduction in a semiconductor break.
As the conduction band in metals is already partially filled at 0 K, many free electrons below the Fermi level acquire energy from an external source or temperature, jump to the conduction band and start behaving like free electrons. Hence, metals contain more free electrons than semiconductors.

Concept: Energy Bands in Conductors, Semiconductors and Insulators
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APPEARS IN

HC Verma Class 11, Class 12 Concepts of Physics Vol. 2
Chapter 23 Semiconductors and Semiconductor Devices
MCQ | Q 1 | Page 418
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