QS Study

The resistivity of a material is the characteristic of that particular material. The materials can be broadly classified into conductors and insulators. The metals and alloys which have low resistivity of the order of 10-6 – 10-8 Ω m are good conductors of electricity. They carry current without appreciable loss of energy.

Example: silver, aluminium, copper, iron, tungsten, nichrome, manganin, constantan.

The resistivity of metals increase with increase in temperature. Insulators are substances which have very high resistivity of the order of 108 – 1014 Ω m. They offer very high resistance to the flow of current and are termed non−conductors.

Example: glass, mica, amber, quartz, wood, teflon, bakelite.

In between these two classes of materials lie the semiconductors (Table). They are partially conducting. The resistivity of semiconductor is 10-2 – 104 Ω m. Example: germanium, silicon.

Table: Electrical resistivities at room temperature