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Question: 1
How can the strain energy be determined from the force extension graph?
Answer: 1
1-45Strain energy can be determined from the force extension graph according to the following relation
Strain energy :1/2 l1F1
Question: 2
Define cell unit.
Answer: 2
2-45A crystalline solid consists of three dimensional pattern that repeat itself over and over again,This smallest three dimensional basic structure is called unit cell.
Question: 3
Define volumetric strain.
Answer: 3
3-45When the applied stress change the volume,then the change in volume per unit volume is called volumetric strain.
Question: 4
Define module of elasticity.
Answer: 4
4-45The ratio of stress to strain is constant for a given material ,provided the external applied force is not too great called modulus of elasticity.
modulus of elasticity=stress/strain
Question: 5
Differentiate between ductile and brittle substance,Give their examples.
Answer: 5
5-45Ductile substance:Substance that undergo plastic deformation unit they break are called ductile substance.Lead copper,and wrought iron are ductile.
Brittle substance: The substance which break just after the elastic limit reached are known as brittle substance.Glass and high carbon steel are brittle.
Question: 6
Define crystal lattice.
Answer: 6
6-45The whole structure obtained by the repetition of unit cell is known as crystal lattice.
Question: 7
Distinguished between elasticity and plasticity.
Answer: 7
7-45Elasticity: In deformed crystalline solid,the atoms return to their equilibrium position after the removal of external force.This ability of the body to return to its original shape is called elasticity.
Question: 8
Define polymeric solid with example.
Answer: 8
8-45Polymers are solid materials with a structure that is intermediate between order and disorder,They can be classified as partially or poorly crystalline solids.For example plastic,rubber.
Question: 9
Define stress and strain,What are their units.
Answer: 9
9-45The force applied on unit area to produce any change in the shape,volume or length of the body is called stress,its SI units is pascal.
And strain is the measure of deformation of solid when stress is applied to it.It has no unit.
Question: 10
Define crystalline and amorphous.
Answer: 10
10-45Crystalline: The solid in which there is a regular and periodic arrangements of the atoms and molecule are crystalline solids.
Amorphous: The solid in which there is no regular arrangement of molecules like that in crystalline solids are called amorphous solid. for example ordinary glass.
Question: 11
What is meant by strain energy?
Answer: 11
11-45The amount of P.E stored in a material due to displacement of its molecule from its equilibrium position.under the action of stress is called strain energy,Strain energy can be determined from the force extension graph according to the following reasons<div>Strain energy=1/2L<sub>1</sub>F<sub>1</sub></div>
Question: 12
Define young modulus and shear modulus.
Answer: 12
12-45The ratio of tensile stress to tensile strain is called young modulus.
Question: 13
Differentiate between tensile stress and shear modes of stress and strain.
Answer: 13
13-45Tensile Stress: A stress that cause the change in length of an object is called tensile stress.
Shear stress: A stress that cause the change in shape of an object is called shear stress.
Tensile stain:If the strain is due to tensile stress it is called tensile strain.A strain produced in the object when it is subjected to shear stress is called shear strain.
Question: 14
What are glassy solids?Do they possessed property of flow?
Answer: 14
14-45Amorphous solids are called as glassy solids.Any non-crystalline solid in which the atoms and molecules are not organized in a definite lattice pattern is called glassy solid.NO they do not possess the property of flow.
Question: 15
Describe the difference between proportional limit and elastic limit.
Answer: 15
15-45Proportional Limit: The greatest stress that a material can endure without losing straight line proportionally between stress and strain.Hooke's law is obeyed in this region.
Question: 16
Define Fracture stress.
Answer: 16
16-45Once the limit of ultimate tensile stress (UTS) is crossed,the material breaks and the stress is called fracture stress.
Question: 17
Define UTS of a material.
Answer: 17
17-45The maximum stress that a material can withstand is called ultimate tensile stress.
Question: 18
What is meant by strain energy?How can it be determined from the force extension of graph?
Answer: 18
18-45The amount of P.E stored in a material due to displacement of its molecule from its equilibrium position.under the action of stress is called strain energy,Strain energy can be determined from the force extension graph according to the following reasons
Strain energy=1/2L1F1
Question: 19
How n type semiconductors are formed?
Answer: 19
19-45When a silicon crystal is doped with a pentavalent element,e.g arsenic,antimony or phosphorus etc.four valence electrons of the impurity atom form covalent bond with the four neighbouring Si atoms,while the fifth valence electrons provide a free electron in the crystal.Such a doped semiconductor is called n type semiconductor.
Question: 20
Define elastic limit and Yield point.
Answer: 20
20-45The greatest stress that a material can endure without any permanent deformation is called elastic limit.This kind of behavior is called elasticity.
Yield point: The point on the stress-strain curve beyond which if stress is further increased then permanent deformation takes place in the given specimen.This is called yield point.
Question: 21
Define yield point and ultimate tensile stress.
Answer: 21
21-45Yield point: The point on the stress-strain curve beyond which if stress is further increased then permanent deformation takes place in the given specimen.This is called yield point.
Ultimate tensile stress: The maximum stress that a material can withstand called ultimate tensile stress.
Question: 22
Differentiate between amorphous and polymeric solid.
Answer: 22
22-45Amorphous solid,any non-crystalline solid in which the atoms and molecules are not organized in a definite lattice pattern,such solid include glass ,plastic and gel.
Question: 23
What is the difference between intrinsic and extrinsic semiconductors?
Answer: 23
23-45Intrinsic Semiconductor:A semiconductor in its extremely pure form is known as Intrinsicsemiconductors,Pure elements of silicon and germanium are Intrinsic semiconductors,These semiconductors elements have atoms with four valence electrons.
Question: 24
Describe the energy band picture of semiconductors.
Answer: 24
24-45In semiconductors,valence band and conduction is partially filled and they have a very narrow forbidden energy gap.
Question: 25
Define stress and write its formula.
Answer: 25
25-45It is defined as the force applied on unit are to produce any change in shape,volume or length of a body.Its formula is
Stress=Force/Area
Question: 26
How the conductivity of semiconductor can be raised?
Answer: 26
26-45The conductivity of a semiconductor can be raised by the process of doping in which small number of impurity atoms are added to pure semiconductors.
Question: 27
Explain what is curie temperature?
Answer: 27
27-45The temperature at which the domains of ferromagnetic material start losing their orderliness is called Curie temperature,For example the curie temperature of iron is 750oC.
Question: 28
Write the used of superconductors.
Answer: 28
28-45Superconductors can be used in :
- Magnetic Resonance Imaging
- Powerful but small electric motors
- Fast computer chips
- Magnetic Levitation Trains
Question: 29
Define superconductors.
Answer: 29
29-45The materials whose resistivity becomes zero below a certain temperature are called superconductors.For example mercury becomes super conductor below 4.2 k temperature.
Question: 30
Distinguished between a valence and a conduction band.
Answer: 30
30-45Valence bond: The energy band occupied by valence electrons is called the valence band.
Question: 31
Define insulators ,conductors and semiconductors.
Answer: 31
31-45Insulator: Those substance which have valence electrons tightly bound to their atoms are called insulators.
Conductors: Those substance which have plenty of free electrons for electrical conduction are called conductors,
Semiconductors:Those substance which have intermediate range of conductivities are called semiconductors e.g germanium and silicon.
Question: 32
Describe energy band picture of insulators.
Answer: 32
32-45Insulators are those materials in which valence electron are bound to very tight to their atoms and are not free.In terms of energy bands,it means that an insulator has:
- An empty conduction band
- A full valence band
- A large energy gap
Question: 33
What is critical temperature in super conductivity?
Answer: 33
33-45The temperature below which the resistivity of a material falls to zero is called critical temperature.For example mercury.
Question: 34
Compare the electrical behavior of conductor and semiconductor in terms of energy band theory.
Answer: 34
34-45On the basic of energy band theory
In conductors,free electrons are available for conduction,Valence and conduction bands largely overlap each other and In semiconductors ,valence band and conduction band is partially filled and they have a very narrow forbidden energy gap.
Question: 35
Define polymerization,write two examples of polymeric solid
Answer: 35
35-45Polymers are found by polymerization reaction,.In these reaction relatively simple molecule are chemically combined into massive long chain molecule or three dimensional structure.
Polythene and nylon are example of polymeric solids.
Question: 36
What are paramagnetic Substance?Give an example
Answer: 36
36-45The solid in which the orbital and spin axes of the electrons in an atom are so oriented that their magnetic field support each other are called paramagnetic substance.For example ozone,platinum etc
Question: 37
What does are of hysteresis loop tell?
Answer: 37
37-45The area of the loop is the measure of the energy needed ti magnetize and demagnetize the specimen during each cycle of the magnetizing current,This is the energy required to do work against internal friction of the domains.This work is dissipated as heat.It is called hysteresis loss.
Question: 38
Define coercivity of a material.
Answer: 38
38-45To demagnetize the material the magnetizing current is reserved and increased to reduce the magnetization to zero.This is known as coercive current,And this process is called coercivity.
Question: 39
What is meant by hysteresis loss?
Answer: 39
39-45The area of the loop is the measure of the energy needed to magnetize and demagnetize the specimen during each cycle of the magnetizing current.This is energy required to do work against internal friction of the domains,this work is dissipated as heat.It is called hysteresis loss.
Question: 40
Distinguished between p-type semiconductor and n-type semiconductor.
Answer: 40
40-45p-type semiconductor:When a trivalent impurity such as aluminium is added into the semiconductor,holes are generated and p type semiconductor is formed.Holes are positive charge carrier.
Question: 41
Define retantivity.
Answer: 41
41-45When the current is reduced to zero,the material still remains strongly magnetized which is known as retantivity.
Question: 42
Define Saturation and Remanence of Hysteresis Loop.
Answer: 42
42-45Saturation: The material is said is reduced to magnetically saturated when magnetic flux density reaches a maximum value.
Remanence: When the current is reduced to zero,the material still remains strongly magnetize.It is due to the tendency of domains to stay partly in line,once they have been aligned,It is called remanence or relativity.
Question: 43
Distinguished between soft magnetic material and hard magnetic materials.
Answer: 43
43-45Soft magnetic: The materials in which their domains can be easily orientated on applying external magnetic field and also return to original positions when field is removes.E.g iron.
Question: 44
What is meant by para and ferromagnetic substance?
Answer: 44
44-45The orbits and the spin axes of the electrons in an atom are so oriented that their field spot each other and the atom behaves like a tiny magnet.Substance with such atoms are called paramagnetic substance e.g iron.
There are some solid substance in which the atom cooperate with each other in such a way so as to exhibit a strong magnetic field there are called ferromagnetic substance.
Question: 45
What is meant by Ferromagnetic substance?
Answer: 45
45-45In ferromagnetic substance the atoms cooperate with each other in such a away so as to exhibit a strong magnetic field.In ferromagnetic substance there exists a small region called domain.
