MATERIALS SCIENCE AND ENGINEERING DEPARTMENT FALL 2016-2017 MSE 427- ELECTRONIC, OPTİC and MAGNETIC MATERIALS and DEVICES

HOMEWORK-I

1. Write equations for the (a) macroscopic and (b) microscopic forms of Ohm’s law.

Define the symbols in each of the equations and indicate their SI units.

2.A wire 0.40 cm in diameter must carry a 25 A current. (a) If the maximum power dissipation along the wire is 0.025 W/cm, what is the minimum allowable electrical conductivity of the wire (give answer in SI units)? (b) What is the current density in the wire?

3. Discuss the effect of followings on resistivity of pure metals - temperature - structural defects - elements that form solid solutions 4. Tin-bronze has a composition of 89wt% Cu and 11wt% Sn, and consists of two phases at room temperature: 25 wt.% -phase and 75 wt.% -phase. Compute the room temperature conductivity of this alloy.

Phase Electrical resistivity (-m) Density (g/cm3)

1.88x10-8 8.94

5.32x10-7 8.25

5. Explain the electrical conductivity of metals, insulators and semiconductor by use of proper energy-band

diagram.

6. How conductivitiy occurs in intrinsic and extrinsic semiconductor materials (both for n- and p-type) Explain

using schematic drawings? Compare their conductivities () by use of conductivity equation.

7. If n-doped and p-doped Silicon is trying to be produced, what elements can be used for each? Which group of

elements, either IIIA or IVA group is suitable?

8. Discuss the variables which effect carrier concentration and carrier mobility. 9.A semiconductor is made by adding boron to silicon to give an electrical resistivity of 1.90 m. Calculate the concentration of carriers per cubic meter in the material. Assume p = 0.048 m2/(V s). 10.1023 m-3 arsenic atoms are added to high-purity silicon.

a) Is this material n-type or p-type? b) Calculate the room temperature electrical conductivity of this material c) Compute the electrical conductivity at 100oC.(Hint: make use of attached figures)

impurity concentration (m-3)

MATERIALS SCIENCE AND ENGINEERING DEPARTMENT FALL 2016-2017 MSE 427- ELECTRONIC, OPTİC and MAGNETIC MATERIALS and DEVICES

HOMEWORK-II

1. (a) A simple plate capacitor is desired to store 6.5x10-5 C at a potential of 12.000 V. If the area of the plates

is 3.0x10-5 m2 and the distance between the plates is 0.18 mm, which of the following dielectric material

given in Table you may choose?

(b) In addition to dielectric constant, what other variables play important role when choosing a dielectric

materials in capacitors? Explain briefly.

(b) Why is BaTiO3used for high-value small, flat disc capacitor?

2. By use of schematic drawings, describe the piezoelectric effect for producing an electrical response with

the application of pressure. Do the same for producing a mechanical response by the application of an

electrical force. Gives examples of applications for two cases.

3. Explain briefly why ferroelectric behavior ceases above curie temperature.

MATERIALS SCIENCE AND ENGINEERING DEPARTMENT FALL 2016-2017 MSE 427- ELECTRONIC, OPTICAL and MAGNETIC MATERIALS and DEVICES

HOMEWORK-III

1- (a) Draw electromagnetic spectrum and label the regions according to wavelength of radiation

(b) Write equation relating the energy of electromagnetic radiation to its wavelength and frequency, and

also compare the relative energies of visible light, ultraviolet light and infrared radiation.

2- If ordinary light is transmitted from air into a 1 cm thick sheet of polymethacrylate (n=1.5), is the light

sped up or slowed down upon entering the plastic? Explain.

3- Explain why cut diamonds sparkle.

4- (a) Light travels from air into an optical fiber with an index of refraction of 1.44. If the angle of incidence

on the end of the fiber is 22o, what is the angle of refraction inside the fiber? (b) Suppose that light travelling in optical fiber. What is the critical angle for light to be totally reflected

when leaving fiber and entering the air.

5- Explain why gold is yellow in color and silver is ‘’silvery’’.

6- Ordinary light strikes the flat surface of a transparent material with a linear absorption coefficient () of

0.04 cm-1. If the plate of the material is 0.80 cm thick, calculate the fraction of light absorbed by the plate.

7- Calculate the transmittance for a flat glass plate 6.00 mm thick with an index of refraction (n) of 1.51 and

linear absorption coefficient () of 0.03 cm-1.

8- Explain the luminescence effect operating in a fluorescent lamp.

9- (a) Show the basic elements of an optical-fiber communication system and describe the function of each

element briefly.

(b) What types of impurities are detrimental to light loss in optical fibers?

(c) How do GeO2 and F affect the refractive index of the silica glass?

(d) How is light loss minimized in optical fibers? Explain showing the structure of fibers.

10- What is the significance of Tc, Hc, and Jc for a superconductor?

11- Describe Meisner effect and the difference between type I and type II superconductors.

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MATERIALS SCIENCE AND ENGINEERING DEPARTMENT FALL 2016-2017 MSE 427- ELECTRONIC, OPTICAL and MAGNETIC MATERIALS and DEVICES

HOMEWORK-IV

1-What is the origin of magnetism and how do we observe magnetic field lines?

2- Define Magnetic permeability, Magnetic Susceptibility. 3-What are the types of magnetism? Define each of them. 4- What are the well known metallic ferromagnetic materials? Why do they display ferromagnetic behavior? Explain in terms of electronic structure. 5-How temperature effects ferromagnetic behavior? 6-What is magnetic domain and how are they effected from external field(H)? Use proper drawings. 7-How most stable domain structure is obtained in a ferromagnetic material? 8-Define total potential energy of a ferromagnetic material. Write down each components affecting total potential energy. 9-Draw hysteresis loop of a magnetic material and define each critical point on the curve. 10-Compare and contrast hysteresis loops of hard and soft magnetic materials? Give examples for hard and soft magnetic materials. 11-Discuss the effect of magnetic annealing on magnetic behavior of ferromagnetic materials.

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