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Which material have negative temp. coefficient.

Which material have negative temp. coefficient. Correct Answer Carbon

Electrical Materials:

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


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 (e.g. Carbon, Silicon, etc.)
  • 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,

[ alt="F1 Nakshtra 16-08-21 Savita D1" src="//storage.googleapis.com/tb-img/production/21/08/F1_Nakshtra_16-08-21_Savita_D1.png" style="width: 456px; height: 157px;">

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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