EX-504-C Electrical and Electronics Materials - Jun 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. 7 Marks
   aDiscuss the classification of engineering materials in detail.
   How to answer

   • Definition of engineering materials
   • Broad classification: metals, ceramics, polymers, composites, semiconductors
   • Sub-classification with examples
   • Brief properties and applications of each class
2. 7 Marks
   bWhat are commonly used conducting materials and what are their properties?
   How to answer

   • List commonly used conducting materials: copper, aluminium, etc.
   • Electrical, mechanical and thermal properties
   • Comparison of conductivity, cost, strength
   • Applications in electrical engineering
3. 7 Marks
   aWhat is dielectric loss and dissipation factor? Discuss factors affecting dielectric loss.
   How to answer

   • Definition of dielectric loss and dissipation factor $\tan\delta$
   • Power loss expression in dielectric
   • Factors: frequency, temperature, humidity, voltage
   • Diagram of loss angle
4. 7 Marks
   bDescribe briefly the class of insulator.
   How to answer

   • Definition and role of insulators
   • Classification: gaseous, liquid, solid, etc.
   • Classes Y, A, E, B, F, H, C with temperature limits
   • Examples and applications
5. 7 Marks
   aDerive an expression for carrier concentration of an electron in intrinsic semiconductor.
   How to answer

   • Intrinsic semiconductor and Fermi level assumption
   • Density of states in conduction band
   • Fermi-Dirac distribution approximation
   • Integration to get $n = N_c \exp[-(E_c-E_F)/kT]$ and $n=p=n_i$ form
6. 7 Marks
   bWhat is hall effect? Derive an expression of hall coefficient RH for n-type semiconductor. Write its applications and importance.
   How to answer

   • Definition of Hall effect and Hall voltage
   • Force balance $qE_H = qv_dB$ derivation
   • Hall coefficient $R_H = -1/ne$ for n-type
   • Applications: carrier type, concentration, mobility measurement
7. 7 Marks
   aWhat are hard and soft magnetic materials on the basis of magnetic susceptibility?
   How to answer

   • Definition of magnetic susceptibility
   • Hard magnetic materials: high coercivity, hysteresis
   • Soft magnetic materials: low coercivity, high permeability
   • Examples and uses
8. 7 Marks
   bExplain ferromagnetism and anti ferromagnetism in detail.
   How to answer

   • Domain and exchange interaction concept
   • Ferromagnetism: parallel alignment, examples
   • Antiferromagnetism: antiparallel equal moments
   • Temperature dependence and Neel temperature
9. 7 Marks
   aWhat is superconductivity? What are its applications?
   How to answer

   • Definition of superconductivity and critical parameters
   • Zero resistivity and Meissner effect
   • Types and critical temperature
   • Applications: magnets, MRI, power cables
10. 7 Marks
    bWhy $SF_6$ gas is used for GIS application? What are its advantages?
    How to answer

    • Properties of $SF_6$ gas: dielectric strength, inertness
    • Suitability for Gas Insulated Switchgear (GIS)
    • Advantages: compactness, safety, low maintenance
    • High voltage insulation and arc quenching
11. 7 Marks
    aDescribe the testing for transformer oils.
    How to answer

    • Purpose of transformer oil testing
    • Tests: breakdown voltage, acidity, moisture, viscosity
    • Procedure for each test
    • Permissible limits and interpretation
12. 7 Marks
    bExplain photoconductive cells and photovoltaic cells.
    How to answer

    • Principle of photoconductivity and photovoltaic effect
    • Construction and working of photoconductive cell
    • Construction and working of photovoltaic cell
    • Characteristics and applications
13. 7 Marks
    aExplain conductor materials used in electrical machines.
    How to answer

    • Requirements of conductors in machines: conductivity, strength
    • Copper, aluminium, winding wires, brushes
    • Insulated conductors and commutator materials
    • Selection criteria for machines
14. 7 Marks
    bWhat are ultralight materials and metallic foams? Explain.
    How to answer

    • Definition of ultralight materials
    • Definition and structure of metallic foams
    • Properties: low density, high strength-to-weight
    • Applications
15. 14 Marks
    Write short notes on the following (any two):

    1. a)Avalanche photodiode
    2. b)Materials for Busbar.
    3. c)Varister
    4. d)Magnetization curve
    5. e)MHD generator
    How to answer

    • Select any two topics from list
    • Principle, construction and working for each
    • Key characteristics/formula/curve
    • Applications with neat diagram where needed