Ee 3903: Electronic Materials - Practice Quiz I
This practice quiz has been created for the students taking Electronic Materials (EE 3903) course offered in Spring 2015 in the Department of Electrical Engineering at Kennesaw State University. The quiz aims to help self evaluate student's preparation on the understanding of the subject matter in an efficient way and does NOT contribute to the final grade.
- 1.
Which of the following can NOT be determined from the Hall measurement?
- A.
Carrier mobility
- B.
Carrier type
- C.
Carrier lifetime
- D.
Carrier concentration
Correct Answer
C. Carrier lifetimeExplanation
The Hall measurement technique is used to determine the carrier mobility, carrier type, and carrier concentration in a material. However, it cannot directly determine the carrier lifetime. Carrier lifetime is typically measured using other techniques such as transient photocurrent or time-resolved photoluminescence. Therefore, the correct answer is carrier lifetime.Rate this question:
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- 2.
Consider a CuZn antisite defect formed in a CZTS film. Here CuZn means –
- A.
A copper atom is replaced by a zinc atom
- B.
A zinc atom is replaced by a copper atom
- C.
Sulfur atoms replace both copper and zinc atoms
- D.
Tin atoms replace both copper and zinc atom
Correct Answer
B. A zinc atom is replaced by a copper atomExplanation
In a CuZn antisite defect, a zinc atom is replaced by a copper atom. This means that in the CZTS film, there is a substitution of a copper atom for a zinc atom. This type of defect can occur due to the similar size and charge of copper and zinc atoms, allowing for their interchange in the crystal lattice.Rate this question:
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- 3.
For a non-polar covalent bond between two atoms A and B, which of the following is true?
- A.
A is more electronegative than B
- B.
B is more electronegative than A
- C.
Both A and B have same electronegativity
- D.
Both A and B must be metals
Correct Answer
C. Both A and B have same electronegativityExplanation
In a non-polar covalent bond, the two atoms share electrons equally because they have the same electronegativity. This means that neither atom is more electronegative than the other. The electronegativity of an atom determines its ability to attract electrons in a bond. Therefore, if both atoms have the same electronegativity, it indicates that they have an equal ability to attract electrons, resulting in a non-polar covalent bond.Rate this question:
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- 4.
Si has the following crystal structure:
- A.
Simple Cubic
- B.
Face Centered Cubic
- C.
Body Centered Cubic
- D.
Diamond
Correct Answer
D. DiamondExplanation
The given crystal structure, diamond, is a type of lattice structure in which each carbon atom is bonded to four other carbon atoms in a tetrahedral arrangement. This results in a highly symmetric and tightly packed structure. Diamond is known for its exceptional hardness and high refractive index, making it a valuable material for various industrial applications and jewelry.Rate this question:
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- 5.
Edge Dislocation is a –
- A.
Zero dimensional defect
- B.
One dimensional defect
- C.
Two dimensional defect
- D.
Three dimensional defect
Correct Answer
B. One dimensional defectExplanation
An edge dislocation is a type of crystal defect that occurs when an extra half-plane of atoms is inserted into a crystal lattice. This results in a region where the atomic arrangement is disrupted and creates a one-dimensional defect line along the edge of the extra half-plane. Therefore, an edge dislocation is considered a one-dimensional defect.Rate this question:
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- 6.
In XRD pattern, we observe a peak when scattered X-rays from the atoms in the crystal –
- A.
Do not interfere at all
- B.
Are completely out of phase
- C.
Make constructive interference
- D.
Make destructive interference
Correct Answer
C. Make constructive interferenceExplanation
In an XRD pattern, when scattered X-rays from the atoms in the crystal make constructive interference, it means that the waves are combining in a way that results in a peak. This occurs when the X-rays are in phase and their peaks and troughs align, amplifying the intensity of the scattered X-rays. This constructive interference pattern provides information about the arrangement of atoms in the crystal lattice and can be used to determine the crystal structure.Rate this question:
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- 7.
Atomic number of Phosphorus is 15. The number of valence electrons in Phosphorus is –
- A.
3
- B.
4
- C.
5
- D.
6
Correct Answer
C. 5Explanation
The atomic number of an element represents the number of protons in its nucleus. Phosphorus has an atomic number of 15, indicating that it has 15 protons. The number of valence electrons in an atom is equal to the number of electrons in its outermost energy level. In the case of Phosphorus, its electron configuration is 2-8-5, meaning it has 5 valence electrons.Rate this question:
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- 8.
If the mean scattering time of electrons in a metal increases, then –
- A.
Mobility increases
- B.
Drift velocity increases
- C.
Conductivity increases
- D.
All of the above
Correct Answer
D. All of the aboveExplanation
If the mean scattering time of electrons in a metal increases, it means that the electrons spend more time between collisions. This leads to an increase in their mobility, as they have more time to move before being scattered. With increased mobility, the drift velocity of electrons also increases, as they can move faster in the presence of an electric field. Additionally, increased mean scattering time implies that there are fewer collisions, allowing the electrons to move more freely and enhancing the overall conductivity of the metal. Therefore, all of the above options are correct.Rate this question:
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- 9.
A deep level impurity creates an electronic energy level at the following position –
- A.
Within the bandgap and very close to the valence band
- B.
Within the bandgap and very close to the conduction band
- C.
Within the bandgap and away from both conduction and valence bands
- D.
Above the conduction band
Correct Answer
C. Within the bandgap and away from both conduction and valence bandsExplanation
A deep level impurity creates an electronic energy level within the bandgap but away from both the conduction and valence bands. This means that the impurity level is not close to either the valence band (where electrons are bound to atoms) or the conduction band (where electrons are free to move and conduct electricity). The impurity level being away from both bands suggests that it is neither donating nor accepting electrons, but rather creating a localized energy state within the bandgap.Rate this question:
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- 10.
Which of the following information can be obtained by X-ray diffraction (XRD) analysis of a crystalline solid?
- A.
Lattice parameters
- B.
Residual Strain
- C.
Crystallinity
- D.
All of the above
Correct Answer
D. All of the aboveExplanation
X-ray diffraction (XRD) analysis is a technique used to study the structure of crystalline solids. It involves shining X-rays onto a sample and analyzing the resulting diffraction pattern. From this analysis, various information about the crystalline solid can be obtained. Lattice parameters refer to the dimensions and arrangement of the crystal lattice, which can be determined by XRD. Residual strain, which is the strain that remains in a material after external forces have been removed, can also be measured using XRD. Additionally, XRD can provide information about the crystallinity of a sample, which refers to the degree of order and regularity in the crystal structure. Therefore, all of the given options can be obtained through XRD analysis.Rate this question:
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- 11.
Grain boundary is a –
- A.
Point defect
- B.
Line defect
- C.
Surface/Plane defect
- D.
Volume defect
Correct Answer
C. Surface/Plane defectExplanation
Grain boundary is a surface/plane defect because it refers to the interface between two grains in a polycrystalline material. It is a region where the crystal structure of one grain transitions to the crystal structure of another grain. This boundary is considered a defect because it disrupts the regular arrangement of atoms within the crystal lattice.Rate this question:
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- 12.
With the increase in temperature, the concentration of vacancies in a crystalline solid –
- A.
Decreases
- B.
Increases
- C.
Remains constant
- D.
Increases till 300K and then decreases
Correct Answer
B. IncreasesExplanation
As the temperature of a crystalline solid increases, the atoms gain more thermal energy and become more mobile. This increased mobility leads to an increase in the number of vacancies, which are empty spaces where atoms should be. However, at very high temperatures, the atoms become so energetic that they can overcome the energy barriers and fill in the vacancies, causing the concentration of vacancies to decrease. Therefore, the concentration of vacancies in a crystalline solid increases with temperature until a certain point (around 300K) and then decreases.Rate this question:
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- 13.
Electrons in a crystal could be scattered by –
- A.
Atoms vibrating due to thermal energy
- B.
Impurity atoms present in the crystal
- C.
Defects present in the crystal
- D.
All of the above
Correct Answer
D. All of the aboveExplanation
Electrons in a crystal can be scattered by various factors. Atoms in the crystal vibrate due to thermal energy, causing the electrons to scatter. Additionally, impurity atoms present in the crystal can also scatter the electrons. Furthermore, defects present in the crystal can also cause scattering of electrons. Therefore, all of the given options - atoms vibrating due to thermal energy, impurity atoms, and defects present in the crystal - can lead to the scattering of electrons.Rate this question:
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- 14.
Hall voltage increases with the increase of –
- A.
Applied magnetic field
- B.
Injected current
- C.
Hall coefficient
- D.
All of the above
Correct Answer
D. All of the aboveExplanation
The Hall voltage is generated when a magnetic field is applied perpendicular to the direction of current flow in a conductor. The Hall voltage is directly proportional to the applied magnetic field, meaning that as the magnetic field increases, the Hall voltage also increases. Additionally, the Hall voltage is inversely proportional to the injected current, so as the current decreases, the Hall voltage increases. Finally, the Hall voltage is also influenced by the Hall coefficient, which is a material-specific property. Therefore, all of the given factors - the applied magnetic field, injected current, and Hall coefficient - affect the Hall voltage.Rate this question:
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- 15.
Defects in a crystalline solid can influence:
- A.
Optical properties
- B.
Electronic properties
- C.
Mechanical properties
- D.
All of the above
Correct Answer
D. All of the aboveExplanation
Defects in a crystalline solid can influence its optical properties by causing light to scatter or absorb differently. They can also affect the electronic properties by introducing energy levels within the band gap or altering the conductivity. Additionally, defects can impact the mechanical properties of a crystalline solid by reducing its strength, ductility, or hardness. Therefore, all of the mentioned properties can be influenced by defects in a crystalline solid.Rate this question:
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- 16.
Which of the following material can achieve highest magnetization?
- A.
Paramagnetic
- B.
Ferrimagnetic
- C.
Ferromagnetic
- D.
Diamagnetic
Correct Answer
C. FerromagneticExplanation
Ferromagnetic materials can achieve the highest magnetization because they have strong permanent magnetic moments that align in the same direction, resulting in a strong overall magnetic field. This alignment is due to the presence of unpaired electrons in the material, which allows for a high degree of magnetization. Paramagnetic materials also have unpaired electrons but their magnetic moments do not align as strongly as in ferromagnetic materials. Ferrimagnetic materials have a combination of aligned and anti-aligned magnetic moments, resulting in a weaker overall magnetization. Diamagnetic materials have all their electrons paired, resulting in a very weak magnetization.Rate this question:
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- 17.
Maximum number of electrons allowed in the L Shell:
- A.
6
- B.
2
- C.
4
- D.
8
Correct Answer
D. 8Explanation
The L shell is the second shell in an atom and can hold a maximum of 8 electrons. Each shell has a specific capacity for electrons, with the first shell (K shell) holding a maximum of 2 electrons, and subsequent shells holding more. Therefore, the correct answer is 8.Rate this question:
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- 18.
The 2nd ionization energy is:
- A.
Equal to the 1st ionization energy
- B.
Less than the 1st ionization energy
- C.
Higher than the 1st ionization energy
- D.
A universal constant for all elements
Correct Answer
C. Higher than the 1st ionization energyExplanation
The second ionization energy refers to the energy required to remove a second electron from an atom or ion. It is generally higher than the first ionization energy because removing a second electron requires overcoming the increased electrostatic forces between the remaining electrons and the positively charged nucleus. This means that it takes more energy to remove a second electron compared to the first. Therefore, the correct answer is "Higher than the 1st ionization energy."Rate this question:
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- 19.
What is the miller indices of the following crystal plane (shaded)?
- A.
(111)
- B.
(001)
- C.
(100)
- D.
(010)
Correct Answer
D. (010)Explanation
The Miller indices represent the orientation of a crystal plane in a crystal lattice. In this case, the shaded crystal plane can be described by the Miller indices (010). The first index (0) indicates that the plane does not intersect the x-axis, the second index (1) indicates that the plane intersects the y-axis at a unit distance, and the third index (0) indicates that the plane does not intersect the z-axis. Therefore, the correct answer is (010).Rate this question:
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- 20.
Which of the following XRD characteristic signifies a higher degree of crystallinity?
- A.
Broad peaks
- B.
Sharp peaks
- C.
Large number of closely spaced peaks
- D.
Showing only (100) and (111) peaks
Correct Answer
B. Sharp peaksExplanation
Sharp peaks in XRD signify a higher degree of crystallinity. This is because sharp peaks indicate that the crystal lattice is highly ordered and the atoms are arranged in a regular pattern. On the other hand, broad peaks suggest a lower degree of crystallinity, indicating that the crystal lattice is less ordered and the atoms are arranged in a more random manner. Large number of closely spaced peaks also indicate a higher degree of crystallinity as it implies that there are multiple planes of atoms in the crystal structure. Showing only (100) and (111) peaks does not provide enough information to determine the degree of crystallinity.Rate this question:
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- 21.
Screw dislocation is a –
- A.
Zero dimensional defect
- B.
One dimensional defect
- C.
Two dimensional defect
- D.
Three dimensional defect
Correct Answer
B. One dimensional defectExplanation
A screw dislocation is a type of linear defect that occurs in crystalline materials. It is characterized by a shear deformation along a single line, resulting in a spiral or helical motion of the crystal lattice. This defect only affects the material in one dimension, as it involves the movement of atoms along a specific line or axis. Therefore, the correct answer is "One dimensional defect."Rate this question:
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- 22.
Two different polycrystalline materials A and B has grain size numbers of 3 and 5 respectively. Which of the following is true?
- A.
A has relatively smaller grains
- B.
B has relatively larger grains
- C.
A has more grains per unit area
- D.
B has more grains per unit area
Correct Answer
D. B has more grains per unit areaExplanation
The grain size number is inversely proportional to the grain size, meaning that a smaller grain size number corresponds to a larger grain size. Therefore, material A with a grain size number of 3 has relatively larger grains compared to material B with a grain size number of 5. Since material B has larger grains, it will have fewer grains per unit area compared to material A. Therefore, the correct answer is that B has more grains per unit area.Rate this question:
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- 23.
Which of the following is NOT correct for indirect bandgap semiconductors?
- A.
CBM and VBM mismatch in the k-space
- B.
Ideal for optoelectronic devices (such as LEDs)
- C.
Recombination process is mediated by phonons
- D.
Recombination process is inefficient
Correct Answer
B. Ideal for optoelectronic devices (such as LEDs)Explanation
Indirect bandgap semiconductors have a mismatch between the conduction band minimum (CBM) and valence band maximum (VBM) in the k-space. This means that electrons cannot easily transition between the two bands without the assistance of phonons. The recombination process in indirect bandgap semiconductors is mediated by phonons, making it less efficient compared to direct bandgap semiconductors. However, indirect bandgap semiconductors are not ideal for optoelectronic devices like LEDs because the inefficient recombination process leads to low emission efficiency.Rate this question:
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- 24.
In a metal, as temperature is increased, mobility of the electrons –
- A.
Increase
- B.
Decrease
- C.
Does not change
- D.
Increases from 0K-273K, then decreases
Correct Answer
B. DecreaseExplanation
As temperature increases in a metal, the mobility of the electrons decreases. This is because as the temperature rises, the atoms in the metal vibrate more vigorously, causing more collisions between the electrons and the atoms. These collisions impede the movement of the electrons, reducing their mobility. Therefore, as temperature increases, the ability of the electrons to move freely within the metal decreases.Rate this question:
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- 25.
If frequency increases, the skin depth of a metal conductor –
- A.
Increases
- B.
Decreases
- C.
Remains same
- D.
Rapidly increases
Correct Answer
B. DecreasesExplanation
When the frequency increases, the skin depth of a metal conductor decreases. Skin depth refers to the depth at which the current density is reduced to approximately 37% of its value at the surface of the conductor. As the frequency increases, the current tends to flow more towards the surface of the conductor, resulting in a decrease in the skin depth. This phenomenon is due to the skin effect, which causes higher frequency currents to concentrate near the surface of the conductor, reducing their penetration into the conductor's interior.Rate this question:
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- 26.
In general, if the electrical conductivity of a metal A is higher than a metal B, which one of the following is true?
- A.
Metal B has higher thermal conductivity
- B.
Metal A has higher thermal conductivity
- C.
There is no relation between electrical & thermal conductivity of metals
- D.
Thermal conductivity of Metal A is exactly half of metal B
Correct Answer
B. Metal A has higher thermal conductivityExplanation
The statement suggests that there is a relationship between electrical conductivity and thermal conductivity in metals. Specifically, if the electrical conductivity of metal A is higher than metal B, then metal A also has higher thermal conductivity. This implies that metals with better electrical conductivity also tend to have better thermal conductivity.Rate this question:
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- 27.
Above the Curie temperature, a ferromagnetic material would behave like a –
- A.
Superconductor
- B.
Diamagnetic material
- C.
Antiferromagnetic material
- D.
Paramagnetic material
Correct Answer
D. Paramagnetic materialExplanation
Above the Curie temperature, a ferromagnetic material loses its magnetic properties and becomes paramagnetic. In the ferromagnetic state, the material has aligned magnetic domains which create a strong magnetic field. However, when the temperature exceeds the Curie temperature, the thermal energy disrupts the alignment of these domains, causing the material to lose its magnetization. In the paramagnetic state, the material still exhibits weak magnetic properties, but they are not as strong or ordered as in the ferromagnetic state.Rate this question:
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- 28.
If the frequency of AC supply is 50 Hz, what would be the corresponding frequency of the humming noise in a power transformer?
- A.
50 Hz
- B.
60 Hz
- C.
100 Hz
- D.
25 Hz
Correct Answer
C. 100 HzExplanation
The humming noise in a power transformer is typically twice the frequency of the AC supply. Since the frequency of the AC supply is 50 Hz, the corresponding frequency of the humming noise would be 100 Hz.Rate this question:
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- 29.
A soft ferromagnetic material must have which of the following property?
- A.
High Coercivity
- B.
Large area within the hysteresis loop
- C.
Low coercivity
- D.
Low remenance
Correct Answer
C. Low coercivityExplanation
A soft ferromagnetic material must have low coercivity. Coercivity refers to the ability of a material to resist changes in its magnetization. In the case of soft ferromagnetic materials, they are easily magnetized and demagnetized with low applied magnetic fields. This low coercivity property allows for efficient and easy manipulation of the magnetic domains in the material, making it suitable for applications such as transformers, electric motors, and magnetic recording devices.Rate this question:
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- 30.
Domain walls in a ferromagnetic material are formed in order to –
- A.
Increase magnetization
- B.
Increase saturation flux density
- C.
Decrease magnetostatic energy
- D.
Decrease hysteresis loss
Correct Answer
C. Decrease magnetostatic energyExplanation
Domain walls in a ferromagnetic material are formed to decrease magnetostatic energy. In a ferromagnetic material, the magnetic domains have different orientations, causing a nonuniform distribution of magnetic field. This leads to a high magnetostatic energy, which is the energy associated with the interaction between these magnetic fields. By forming domain walls, the material can minimize this energy by allowing the domains to align in a more uniform manner. Therefore, the formation of domain walls decreases the magnetostatic energy in the material.Rate this question:
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.PNG "What is the miller indices of the following crystal plane (shaded)?")
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