EX-504-C Electrical and Electronics Materials - Dec 2025 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. Marks
   aExplain classification of solids from electrical point of view.
   How to answer

   • Classify solids into three categories: conductors, semiconductors, and insulators
   • Explain based on electrical conductivity and band structure
   • Conductors: free electrons, low resistivity
   • Semiconductors: intermediate conductivity, energy gap
   • Insulators: high resistivity, large band gap
2. Marks
   bDistinguish between metals and alloys.
   How to answer

   • Metals: pure elements with metallic bonding
   • Alloys: two or more elements, at least one metal
   • Metals: single phase; alloys: may be multi-phase
   • Differences in electrical conductivity, melting point, hardness
   • Examples: Cu (metal) vs Brass (alloy)
3. Marks
   aExplain the properties and classification of conductor material.
   How to answer

   • Properties: high electrical conductivity, low resistivity, free electrons
   • Temperature coefficient of resistance
   • Classification: good conductors (Cu, Al, Ag), medium conductors
   • Band structure: conduction band partially filled or overlapping
   • Application in wires, cables, and electronic devices
4. Marks
   bDescribe crystal structure of materials.
   How to answer

   • Crystal structure: periodic arrangement of atoms in 3D space
   • Basic types: simple cubic, body-centered cubic, face-centered cubic
   • Lattice parameters and unit cell
   • Relationship between structure and material properties
   • Amorphous vs crystalline materials
5. Marks
   aWhat are insulating materials? Write their properties.
   How to answer

   • Definition: materials with very low electrical conductivity
   • Large band gap preventing electron movement
   • Properties: high electrical resistivity, high dielectric strength
   • Low thermal conductivity, mechanical strength
   • Examples: rubber, ceramic, mica, glass
6. Marks
   bExplain piezoelectricity and ferroelectricity.
   How to answer

   • Piezoelectricity: electric charge generation under mechanical stress
   • Reverse piezoelectric effect: deformation under electric field
   • Ferroelectricity: permanent electric polarization, spontaneous polarization
   • Hysteresis loop, Curie temperature
   • Applications: sensors, actuators, capacitors
7. Marks
   aDefine: Dielectric loss, Dissipation factor, dielectric strength.
   How to answer

   • Dielectric loss: energy loss per cycle in AC field
   • Dissipation factor (tan δ): ratio of loss to stored energy
   • Dielectric strength: maximum electric field without breakdown
   • Relationship between these parameters
   • Temperature and frequency dependence
8. Marks
   bDraw and explain energy band diagrams for conductor and semiconductor.
   How to answer

   • Conductor: overlapping conduction and valence bands or partially filled band
   • Semiconductor: conduction and valence bands separated by small energy gap (Eg)
   • Fermi level position: near top in conductor, middle in semiconductor
   • Electrons and holes in respective bands
   • Energy axis and band structure illustration
9. Marks
   aCompare the intrinsic and extrinsic semiconductors.
   How to answer

   • Intrinsic: pure semiconductor, equal electrons and holes
   • Extrinsic: doped with impurities (donors or acceptors)
   • Conductivity: intrinsic low, extrinsic high
   • n-type and p-type extrinsic semiconductors
   • Temperature dependence and applications
10. Marks
    bExplain the Hall Effect in semi conductor materials with related diagrams and expressions. Also mention its importances in semiconductor materials.
    How to answer

    • Hall Effect: voltage generation perpendicular to current and magnetic field
    • Hall coefficient and Hall voltage expression
    • Lorentz force on charge carriers
    • Determination of carrier type (electron or hole) and concentration
    • Importance: semiconductor characterization, mobility measurement, device fabrication
11. Marks
    aWrite short notes on: Photo transistors, Light dependent resistors.
    How to answer

    • Phototransistor: semiconductor device sensitive to light, uses photocurrent amplification
    • Construction: base-collector junction sensitive to light
    • Light dependent resistor: resistance decreases with increasing light intensity
    • LDR materials: CdS, CdSe
    • Applications: light sensors, switches, automatic control systems
12. Marks
    bCompare Diamagnetic, Paramagnetic and Ferromagnetic material.
    How to answer

    • Diamagnetic: weak negative susceptibility, repelled by magnetic field
    • Paramagnetic: weak positive susceptibility, attracted to magnetic field
    • Ferromagnetic: strong positive susceptibility, permanent magnetization
    • Magnetic moment alignment differences
    • Examples and applications of each type
13. Marks
    aDescribe Soft and Hard magnetic materials.
    How to answer

    • Soft magnetic: low coercivity, easy demagnetization, narrow hysteresis loop
    • Examples: iron, silicon steel, nickel
    • Hard magnetic: high coercivity, permanent magnetization, wide hysteresis loop
    • Examples: steel, cobalt alloys, rare earth magnets
    • Applications: transformers (soft), permanent magnets (hard)
14. Marks
    bWrite physical and electrical properties of SF6.
    How to answer

    • SF6: colorless, odorless, non-toxic gas
    • Physical properties: high density, boiling point -63.8°C
    • Electrical properties: excellent insulating gas, high dielectric strength
    • High chemical stability and thermal stability
    • Applications: circuit breakers, transformers, high voltage equipment
15. Marks
    aWhat do you understand by superconductivity. Also write its application.
    How to answer

    • Superconductivity: zero electrical resistance below critical temperature (Tc)
    • Meissner effect: expulsion of magnetic field from superconductor
    • Cooper pairs and BCS theory
    • Critical temperature, critical field, critical current
    • Applications: MRI magnets, power transmission, particle accelerators, magnetic levitation
16. Marks
    bWhat are the nano-materials and ultra-light materials?
    How to answer

    • Nanomaterials: materials with dimensions 1-100 nm, unique properties due to size
    • Enhanced strength, electrical and thermal properties at nanoscale
    • Examples: carbon nanotubes, nanoparticles, graphene
    • Ultra-light materials: very low density materials, high strength-to-weight ratio
    • Examples: aerogels, polymer foams, metallic foams; applications in aerospace and structural applications