9. Properties of Solids

PROPERTIES OF SOLIDS

1. Electric Properties :

On the basis of electrical conductivity the solids can be broadly classified into the three types:

(a) Metals (conductors) 

(b) Insulators 

(c)  Semi-conductors.

Following are salient features of electrical conductance in solids.

(i) The electrical conductivity of metallic conductors is due to the motion of electrons or positive holes (electronic conductivity) or through the motion of ions (ionic conductivity)

(ii) The conductance through electrons is called n-type conduction and through positive holes is called p-type conduction.

(iii) The conductance in insulators and semiconductors is mainly due to the presence of interstitial electrons and positive holes in the solids due to imperfections.

(iv) The conductivity of semiconductors and insulators increases with increase in temperature while that of metals decreases.

(v) Electrical conductivity of metal is in the order of 106–108 ohm–1 cm–1 while that of inculator is of the order of 10–12 ohm–1 cm–1. Semiconductors have intermediate value in the range 10–9 ohm–1 cm–1.

2. Magnetic Properties :

Based on the behaviour of substances when placed in the magnetic field, they are classified into five classes.