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Ece 152: Electrical Engineering Materials Question Paper

Ece 152: Electrical Engineering Materials

Course:Bachelor Of Engineering In Electrical And Computer Engineering

Institution: Moi University question papers

Exam Year:2012

MOI UNIVERSITY
DEPARTMENT OF ELECTRICAL AND COMMUNICATIONS ENGINEERING

ECE 152: ELECTRICAL ENGINEERING MATERIALS

Answer all questions

1. An electrical capacitor is to be made with a sheet of polythene of thickness 0.1mm between the capacitor plates. The dielectrica strength is 4x10^7 V/m

i. Define dielectric strength of a material and the breakdown voltage of a capacitor made from the material. (4mks)

ii. What is the breakdown voltage of the capacitor above? (3mks)

iii. A multi-layer capacitor is to be designed using a BaTiO3 formulation containing SrTiO3. The dielectric constant of the material is 3000. Calculate the capacitance of a multi-layer capacitor consisting of 100 layers connected in parallel using nickel electrodes. The area of each layer is 10mm x 5mm and the thickness of each layer is 10 micrometre. (3mks)

2.
i. Briefly describe the phenomenon of refraction as relates to a media. (2mks)

ii. Define refractive index for light travelling from material A to material B. (2mks)

iii. A beam of red light with a wavelength in vacuum of 650 nm enters an insulator with an effective dielectric constant of 1.7 at the frequencies of visible light. What will be the frequency, angular frequency, velocity and wavelength of this light when travelling within the insulator? (3mks)

iv. What is electromagnetic constant? Explain its significance. (3mks)

3.
i. Explain the differences in diamagnetic, paramagnetic materials and ferromagnetic and ferrimagnetic materials using their relative permeabilities. Give examples of each material and its practical application. (6mks)

ii. Explain the importance of the Curie temperature in ferromagnetic materials. What is the behavior of the dielectric constant of ferroelectric materials at the curie temperature? (4mks)

Ece 152: Electrical Engineering Materials Question Paper

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