Comprehensive notes for Chapter 17 Physics of Solids. Covers Classification of Solids, Stress, Strain, Modulus of Elasticity, Band Theory, Superconductors, and Magnetic Properties.
Crystalline Solids: Regular arrangement of atoms/molecules. Definite melting point. Example: Metals, NaCl.
Amorphous (Glassy) Solids: No regular arrangement. No definite melting point. Example: Glass.
Polymeric Solids: Intermediate structure. Long chain molecules. Example: Plastics, Nylon.
Stress ($$ \sigma $$): Force per unit area. $$ \sigma = F/A $$. Unit: Pascal (Pa).
Strain ($$ \epsilon $$): Fractional change in dimension. No units.
Modulus of Elasticity: Ratio of stress to strain within elastic limit.
Elastic Limit: Max stress withstandable without permanent deformation.
Yield Point: Point beyond which permanent deformation occurs.
Plasticity: Permanent deformation after stress removal.
Strain Energy: Work done in deforming molecules. $$ Work = \frac{1}{2} F \times \Delta l $$ (Area under F-l graph).
Energy Band Theory: Explains conductivity based on energy gap (Eg).
Intrinsic Semiconductor: Pure (Si, Ge). Extrinsic: Doped (N-type or P-type).
Critical Temperature (Tc): Temperature below which resistance becomes zero.
Applications: MRI, Maglev trains, Powerful electromagnets.
High Tc: Ceramic superconductors (e.g., YBCO at 90K).
Origin: Orbital and spin motion of electrons.
Hysteresis Loop: B-H curve. Area represents energy loss. Soft Magnetic Material: Small area (Iron). Hard Magnetic Material: Large area (Steel).