Copper behaves as a

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UPSC ESE (Prelims) Electronics and Telecommunication Engineering 19 Feb 2023 Official Paper
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  1. conductor always
  2. conductor or dielectric depending on the applied electric field strength
  3. conductor or dielectric depending on the frequency
  4. conductor or dielectric depending on the dielectric current density

Answer (Detailed Solution Below)

Option 1 : conductor always
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Detailed Solution

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Electrical Materials:

The materials used in electrical engineering can be broadly divided into three major types,
1. Conductors
2. Semiconductors
3. Insulators

Conductors (e.g. copper, aluminum, etc.) conduct current very easily while insulators (e.g. glass, mica, paper) practically conduct no current.

In other words, conductors have small resistivity and insulators have a high value of resistivity. The resistivity of semiconductors (e.g. germanium, silicon, etc.) lies between conductors and insulators.

1. Conductors:

  • Conductors are formed by metallic bonds. These bonds are based on a structure of positive metal ions surrounded by a cloud of electrons.
  • Conductors have a positive temperature coefficient of resistivity i.e their resistivity increases with the rise in temperature and vice-versa.
  • Conductors are used to carry current in electric circuits.
  • eg: Copper, Aluminium, Silver, etc


2. Semiconductors:

  • Semiconductors are formed by covalent bonds.
  • Semiconductors have a negative temperature coefficient of resistivity i.e. their resistivity decreases with the rise in temperature and vice-versa
  • Semiconductors are used in the manufacturing of electronic devices (e.g. crystal diodes, transistors, etc.).
     

3. Insulators:

  • Insulators are predominantly covalent compounds. The valence electrons are tightly locked with neighboring atoms and are not available to support the flow of current.
  • Insulators have a negative temperature coefficient of resistivity i.e. their resistivity decreases with the rise in temperature and vice-versa.
  • Insulators are used to confine the current to the desired path.
     

The Temperature vs Resistivity graph for electrical material is shown below,

F1 Nakshtra 16-08-21 Savita D1

Note: When the temperature increases, the atoms of the material vibrate, making the valence electrons present in the valence band shift to the conduction band.

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