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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
On the basis of crystal field theory. Write the electronic confirguration of `d^(6)` in terms of `t_(2g) " and " e_(g)` in an octahedral field when `D_(0) lt P.` |
| Answer» Correct Answer - `t_(2)g^(4) eg^(2)` | |
| 102. |
What is meant by crystal field splitting energy? On the basis of crystal field theory, write the electronic configuration of `d^(4)` in terms of `t_(2g) and e_(g)` in an octahedral field when (i)`Delta_(0)gtP` (ii) `Delta_(0)ltP` |
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Answer» The splitting energy of the degenerate orbitals due to the. presence of ligands in a definite geometry is known as crystal field splitting and the difference of energy between two sets of degenerate orbitals. (i) If `Delta_(0)gt P,` it becomes more energetically favourable for the fourth electron to occupy as `t_(2g)` orbital with configuration `t_(2g)^(4).e_(g)` Thus ligands for which `Delta_(0)gtP` are known as strong field ligands and form low spin complex. (ii) If `Delta_(0)ltP`, the fourth electron enters one of the `e_(g),` orbital giving the configuration `t_(2g)^(3)e_(g),` Ligands for which `Delta_(0)ltP` are known as weak field ligands and form high spin complexes. |
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| 103. |
(a) Based on the nature of intermolecular forces, classify the following solids: Silicon carbide, Argon (b) ZnO turns yellow on heating. Why? (c) What is meant by groups 12-16 compounds? Give an example. |
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Answer» (a) Silicon carbide (sic)=Covalent or network Argon-Molecular (non polar) (b) When ZnO is heated, it loses oxygen `ZnOtoZn^(2+)+(1)/(2)O_(2)+2e^(-)` `Zn^(2+)` ions are entrapped in the interstitial voids and `e^(-)` s in the neighbouring interstitial voids to maintain electrical neutrality. this gives rise to metal excess defect. due to the presence of `e^(-)`s in voids, the colour is yellow. (c) Semiconductors which are prepared by combination of elements of group 12 and group. |
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| 104. |
`(i)` When an `AC` source is connected to an ideal inductor show that the average power supplied by the source ever a complete cycle is zero. `(ii)` A lamp is connected in series with an inductor and an `AC` source. What happens to the brightness of the lamp when the key is plugged in and an iron rod is inserted the indcutor ? Explain. |
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Answer» `(i)` In an ideal inductor current lags by `pi//2` `V=V_(0)sin(wt-pi//2)=-I_(0)sin(pi//2-wt)=-I^(@)coswt` Work done in small time `dt` `dw=Pdt=-V_(0)I_(0)sinwt cos wt dt` `=-(V_(0)I_(0))/(2)sin2wtdt` Average power associated per cycle `P_(av)=(W)/(T)=(I)/(T)int_(0)^(T)dw=-(V_(0)I_(0))/(2T)int_(0)^(T)sin2wt dt=(V_(0)I_(0))/(2T)[(cos2wt)/(2w)]_(0)^(T)` `=(V_(0)I_(0))/(2T)[(cos4pi-cos0)/(2w)]=0`. `(ii) L` will increase `mu_(r)` times, this will increase `X_(L)` and hence, current decrease. So brightness decreases. |
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| 105. |
(i) Define the term drift velocity . (ii) On the basis of electron drift , derive an expression for resistivity of a conductor in terms of number density of free electrons and relaxation time. On what factors does resistivity of a coductor depend ? (iii) Why alloys like constantan and manganin are used for making standard restores ? |
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Answer» (i) Drift velocity is defined as the average velocity with which the free electron gets drifted f in the direction of external electric field applied. (ii) See Q. 27 2012 Set-I O.D., [Page 153] (iii) Low value of temperature coefficient and high specific resistance . |
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| 106. |
`(i)` Derive an expression for drift velocity of free electrons. `(ii)` How many drift velocity of electrons in a metallic conductor vary with increase in temperature ? Explain. |
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Answer» `(i)` Expression for drift velocity : When a potential difference is applied across a conductor, an electric field is produced and free electrons are acted upon by an eletric force `(= -Ee)`. Due to this, electrons accelerate and keep colliding with each other and acquire a constant (average) velocity, `v_(d)` `:. Fe= -Ee=-((V)/(l))e` `:. E=(V)/(l)` As `a=(-F)/(m)=(-ev)/(lm)` and also `v=u+at` `:. u=0`, `t=tau`(relaxation time) `v_(d)=-a tau` `v_(d)=(-eV)/(lm)tau` `(ii)` As temperature is increased no. of collision increases hence `tau` relaxation time decrease but `V_(d)xxtau` so, `V_(d)` decreases. |
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| 107. |
Name and explain the technique that helps in the separation of DNA fragments for DNA recombinant technology experiments. How can these separated DNA fragments be visualised ? |
| Answer» Gel electrophoresis is the technique that helps in the separated of DNA fragments DNA fragments are negatively charged molecules and they can be separated by forcing them to move towards anode under an electic field through medium/matrix. Separation is based on size. The separated DNA fragments can be visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiation. | |
| 108. |
Name the enzymes that are used for the isolation of DNA from bacterial and fungal cells for recombinant DNA technology. |
| Answer» The enzymes used are Lysozyme (bacteria) and Chitinase (fungi). | |
| 109. |
Write any four ways used to introduce a desired DNA segment into a bacterial cell in recombinant technology experiments. |
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Answer» i) The desired DNA segment is inserted into a cloning vector and the bacterial cells can be made to take it up after making them competent by treating them with specific concentration of divalent cations such as calcium. ii) Microinjection iii) Biolistics or gene gun. iv) Disarmed pathogen vector |
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| 110. |
Name the source of the DNA polymerase used in PCR technique. Mention why it is used. |
| Answer» The source is the bacterium Thermus aquatics. It is used because it is thermostable and does not denature at high temperatures. | |
| 111. |
Name the bacterium responsible for the large holes seen in "Swiss Cheese" What are these holes due to? |
| Answer» Swiss cheese is ripened by bacterium Propionibacterium sharmanii which produce `CO_(2).CO_(2)` cause the large holes. | |
| 112. |
Write the events that take place when a vaccine for any disease is introduced into the human body. Or " " Why is a person with cuts and bruises following an accident administered tetanus antitoxin? Give a reasons. |
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Answer» When a vaccine is introduced, it induces the production of antibodies in the body against the antigens of the disease. These antibodies neutralise the antigens at the time of actual infection. They also cause the productionof B and T cells which recognize the pathogen quickly on subsequent exposure. Or " " Tetanus is caused by a deadly bacterium which require quick response to neutralise. Therefore, preformed antitoxin is administrated to neutralise the effect of the bacterial toxin. |
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| 113. |
Explain the role of each of the following : (i) NaCN in the extraction of silver (ii) `SiO_(2)` in the extraction of copper |
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Answer» (i) During roasting copper pyrites are converted in to mixture of FeO and `Cu_(2)O` To remvoe Fe(basic) an acidic flux silica is added during smelting .FeO then combines with Si `O_(2)` to form ferrous silicate `(Fe SiO_(3))` slag which floats over molten matter (ii) Role of Na CN in he extraction of silver is to do the leaching of silver ore in the presence of air from which the silver is obtained later by replacement `4Ag(s)+8CN^(-)(aq)+2H_(2)O(aq)+O_(2)(g)rarr4[Ag(CN)_(2)]^(-)(aq)+4OH^(-)(aq)` `2[Ag(CN_(2))^(-)](aq)+Zn(s)rarr2Ag(s)+[Z(CN)_(4)^(2-)(aq)]` |
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| 114. |
What is the total number of atoms per unit cell in a face centred cubic (fcc) structure ? |
| Answer» Total number of atoms per unit cell in (face centred cubic) fcc structurs=4 | |
| 115. |
Describe the role of (i) `NaCN` in the extraction of gold from gold ore. (ii) `SiO_(2)` in the extraction of copper from copper matter. (iii) Iodine in the refining of zirconium. Write chemical equations for the involved reactions. |
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Answer» (i) Role of NaCN in the extraction of gold is to do leaching of gold ore in the pressence of air from which the gold is obtained later by replacement. `4Au(s)+8CN^(-)(aq)+2 H_(2)O+O_(2)(g) rightarrow 4[Au(CN)_(2)]^(-)+4 OH^(-)` (ii) `SiO_(2)` is added in copper matter to convert the remaining FeS, FeO to slag `FeO+Si O_(2) rightarrow underset(("slag")) (Fe Si O_(3))` (iii) Iodine is heated with Zirconium to form a volatile-compound which on further heating decompose to give pure zirconium `Zr(impure)+2 I_(2)rightarrowZr I_(4)` `Zr I_(4) rightarrow Zr(pure)+2 I_(2)` |
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| 116. |
Describe the following : - (i) The role of cryolite in electro metallurgy of aluminium. (ii) The role of carbon monoxide in the refining of crude nickel. |
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Answer» (i) In the metllurgy of aluminimum, purified `Al_(2)O_(3)` is mixed with cryolite lowers melting point of the mix and brings conductivity. (ii) CO-forms a volatile complex (Nickel tetralabonyl) `Ni +4 Co overset(300-350K)rarrNi(CO)_(4)` the carbonyl is subjected to higher temperature so that it is decomposed giving a pure metal. `Ni[CO] overset(450-41 K)rarrNi+4CO`. |
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| 117. |
(i) Name the method of refining of nickel (ii) What is the role of cryolite in the extraction of aluminium ? (iii) What is the role of limestone in the extraction of iron from its oxides ? |
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Answer» (i) Mond process. (ii) It makes aluminium a good conductor of electricity and it lowers the fusion (M.P) temperature both from 2323 k to about 1140 K. (iii) At 1123k, limestone decomposes to form CaO and `CO_(2).` CaO act as flux and combine silica (impurity) to form calcium silicate slag. `CaCO_(3) (s)overset(1123k)(to)CaO(s) + CO_(2)(g)` `CaO(s) + SiO(s) to CaSiO_(3) " Calcium silicate (slag)"` |
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| 118. |
Describe the following: (i) Role of depressant in forth floatation process. (ii) Role of silica in the metallurgy of copper. (iii) Role of cryolite in the metallurgy of aluminium. |
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Answer» (i) Role of depressant is to prevent one type of sulphide ore particles from forming the froth with air bubbles. For example : NaCl is used a depressant to separate PbS ore from ZnS ore. (ii) To remove FeO, Silica is added during smelting which form ferrous silicate `(FeSiO_(3))` slag which floats over molten matte and can be easily removed. (iii) Cryolite is added to alumina to make it a good conductor of electricity and to reduce the melting point of mix to around 1140K. |
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| 119. |
(a) What in plasmid? (b) What is meant by ADA dehciency ? How is gene therapy a solution to this problem ? Why is it not a permanent cure ? |
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Answer» (a) Plasmid refers to the extra chromosomal circular DNA molecule that replicate. autonomously in a bacterial cell. (b) Adenosine deaminase (ADA) deficiency. It is associated with (SCID) severe combined immunodeficiency. ADA is very crucial for immune systems to function. The deficiency of ADA causes severe combined immune deficiency disease. The patient lacks functional T-lymphocyteo and fails to fight the infections pathogens. Using the gene-therapy lymphocytes are extracted from the patient’s bone marrow and a normal functional gene for ADA is introduced into these lymphocytes with the help of the retro virus. The lymphocyctes of bone marrow contains the functional ADA gene and reactivate the patient’e immune system. In some children, ADA deficiency can be treated bone marrow transplantation, in other it can be treatedby enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem with both of these approaches that they are not completely curative. |
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| 120. |
What weight of the non-volatile urea (`NH_2- CO - NH_2`) needs to be dissolved in 100g of water in order to decrease the vapour pressure of water by 25%? What will be molality of the solution? |
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Answer» Here, `(P^o-P_s)/(P^o) =25/100or (P^o-P_s)/P_s=25/75` `W_A=100g,W_B=?` For urea, `M_B=60//mol.` for water, `M_A =18g//mol.` `(P^o-P_s)/P_s=n_B/n_A=(W_A//M_B)/(W_A//M_A)` `25/75=(W_B//60)/(100//18)` `or W_B=111g` Molality of the silution `=(111g)/(60gmol^(-1))xx1/(100g)xx100gkg^(-1)` ot 18.5 m. |
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| 121. |
Give one example of an animal which exhibits Oestrous cycle. |
| Answer» Correct Answer - Cows | |
| 122. |
Identify the correct statement : (a) Female of many birds has a pair of dissimilar ZW chromosomes, while the males posses a pair of similar ZZ chromosomes. |
| Answer» Correct Answer - 1 | |
| 123. |
State one reason why breast-feeding the baby acts as a natural contraceptive for the mother. |
| Answer» Breast feeding leads to absence of menstruation (Lactational amenorrhoea) following child birth. Therefore, it acts as a natural method of contraception. However, this method is effective only upto six months following child birth. | |
| 124. |
The conductivity of 0.001 `"mol" L^(-1)` solution of `CH_(3)COOH " is " 3.905 xx 10^(-5) "S" cm^(-1)`. Calculate its molar conductivity and degree of dissociation `(alpha)`. `"Given" lambda^(@) (H^(+)) = 349.6 "S" cm^(2) "mol"^(-1) " and " lambda^(0) (CH_(3)COO^(-)) = 40.9 "S" cm^(2) "mol"^(-1)` (b) Define electrochemical cell. What happens if external potential applied becomes greater than `E_(cell)^(@)` of electrocemical cell? |
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Answer» `wedge_(m) = (K("conductivity") xx 1000)/(M)` `= (3.905 xx 10^(-5) xx 1000)/(0.001)` `=39.055 " cm"^(2)"mol"^(-1)` `=(wedge^(c)m)/(wedge^(@)m) = (39.05)/(wedge^(@)m) " " [wedge_(CH_(3)COOH)^(@) = wedge_(CH_(3)COO^(-))^(@) + wedge _(H)^(@)+` `= 349.6 + 6 +0.9` `=390.5 "S"cm^(2)"mol"^(-1)]` ` = (39.5 xx 10)/(390.5 xx 100) = 0.1` (b) Electrochemical Cell : It is a device to convert chemical energy into electrical energy. It is based upon the redox reaction which is spontaneous. The electrode on which oxidation takes place is called the anode and the electrode, where reduction takes place is called cathode. If, external potential applied becomes greater than `E_(cell)^(@)` of electrochemical cell, then the cell behave as electrolytic cell. |
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| 125. |
Why is Agrobacterium tumefaciens a good cloning vector ? Explain. |
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Answer» The tummer inducing plasmid of Agrobacterium tumefaciens Ti-plasmid has now been modified into a cloning vector which is no more phthogenic to the plants but is still able to use the mechanism to deliver genes of our interest into a variaty of plants. Agrobacterium tamifaciens is a soil bacterium which causes diseases in meny dicot plants . It is able to deliver a picee of DNA known as T-DNA, to transfrom the normal cells into tumor cells and direct these tumor cells to produce to chemicals required by the pathogen. |
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| 126. |
Your advice is sought to improve the nitrogen content of the soil to be used for cultivation of a non leguminous terrestrial crop (a) Recommend two microbes that enrich the soil with nitrogen (b) why do leguminous crops not requirre such enrichment of the soil ? |
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Answer» (a) Rhiobium Anabaena andazotobacter (b) Because they can fix the atomospheric nitrogen Rhizobioum is a bacteria that lives in the roots of these plants .It converts the nitrogen in to the form that can be absorbed by the plant |
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| 127. |
(i) Write down the IUPAC name of the following complex : `[Co(NH_(3))_(5)Cl]^(2+)` (ii) Write the formula for the following complex : Potassium tetrachloridonickelate (II). |
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Answer» (i) Pentaaminechlorido- Cobalt (III). `K_(2)[Ni(Cl)_(4)].` |
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| 128. |
Arrange the following compounds in increasing order of their property as indicated : (i) `underset("(reactivity toward nucleophilic addition reaction)")underset()(CH_(3)COCH_(3),C_(6)H_(5)COCH_(3),CH_(3)CHO`) (ii) `Cl-CH_(2)-COOH, F-CH_(2)-COOH,CH_(3)-COOH`( acidic character) |
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Answer» (i) Increasing order : `C_(6)H_(5)COCH_(3)ltCH_(3)COCH_(3)ltCH_(3)CHO` (ii) `F-CH_(2)-COOHgt Cl-CH_(2)-COOHgtCH_(3)-COOH` |
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| 129. |
Write the reagents required in the following reactions : (i) `CH_(2)=CH-CH_(2)Ohoverset(?)rarrCH_(2)=CH-CHO` (ii) `CH_(3)-COOHoverset(?)rarrCH_(3)-CONH_(2)` |
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Answer» (i) `CH_(2)=CH-CH_(2)Ohoverset(P"C"C//CH_(2)Cl_(2))rarrCH_(2)=CH-CHO` (ii) `CH_(2)-COOHoverset(NH_(3))underset("Heat")rarrCH_(3)-CONH_(2)` |
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| 130. |
What are emulsions ? What are their different types ? Give an example of each type ? |
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Answer» Colloidal solution of liquid in liquid is called as emulsion We have two types of emulsions Oil in water (o/w):In this type of emulsion water is medium and oil is deispersed phase it soluble in `H_(2)O`,Ef.Milk. (i) Water in oil (w/o): In this type of emulsion oil is medium and water is dispersed in to it it is soluble in oil Eg butter. |
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| 131. |
(b) Write the prodcuts (s) in the following: `CH_(3)-COOHoverset(Br2//p)rarr`? (ii) `CH_(3)-CHOoverset(LiAIH_(4))rarr`? (iii) `CH_(3)-underset(O)underset(||)C-CH_(3)overset(Zn-Hg)underset(concHCI)rarr`? |
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Answer» (i) `CH_(2)CI-COOH` (ii)`CH_(3)CH_(2)OH` `CH_(3)CH_(2)CH_(3)` |
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| 132. |
Define Emulsions |
| Answer» When disperesed phase and disperions medium both are liquid eq milk | |
| 133. |
Examine the given defective crystal : Answer the following questions : (i) Is the above defect stoichiometric or non-stoichiometric ? (ii) Write the term used for this type of defect. Give an example of the compound which shows this type of defect. (iii) How does this defect affect the density of the crystal ? |
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Answer» (i) It is stoichiometric defect. (ii) Schottky defect.eg NaCl and Kcl (iii) Like simple vacaney defect, Schottky defect also decreases the density of the substance. Number of such defects in ionic solids in quite significant. |
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| 134. |
Examiine the given defective crystal (i) What type of stoichiometric defect is shown by the the crystal ? (ii) How is the density of the crystal affected by this defect ? (iii) What type of ionic substance show such defect ? |
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Answer» (i) Schottky defect is shown by the mentioned crystal, as equal number of cations and anions are missing in the crystal lattice. (ii) This defect leads to decrease in density, as equal number of the cations and anions are missing from the crystal lattice. (iii) This kind of defect is shown by those ionic substance in which the cations and anions are of almost similar sizes. Examples : `NaCl, KCl and CsCl` |
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| 135. |
Draw a diagrammatic sectional view of a human seminiferous tubule, and label sertoli cells, primary spermatocyte, sperm-atogonium and spermatozoa init. b) Explain the hormonal regulation of the process of spermatogenesis in humans. |
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Answer» b) GnRH is secreted by the hypothalamus. The increased levels of GnRH stimulates the anterior pituitary which then secretes the FSH(Follicle stimulating hormone) and LH (luteinsing hormone). FSH stimulates Sertoli cells to secrete some factors which help in spermiogenesis. LH acts on the Leydig cells and causes the secretion of testorsterone from the testes. |
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| 136. |
Monochromatic light of frequency `6.0xx10^(14)Hz` is produced by a laser. The power emitted is `2.0xx10^-3W`, (a) What is the energy of a photon in the light beam? (b) How many photons per second, on the average, are emitted by the source? Given `h=6.63xx10^(-34) Js` |
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Answer» (i) Energy of one photon `=hv=6.63xx10^(-34)xx6.0xx10^(14)=39.79xx10^(-20)J` (ii) No. of photons per sec . `=("Total Energy/sec")/("Energy of onephoton")=(2.0xx10^(-3))/(39.78xx10^(-20))=5.0276xx10^(15)`Photons per sec. |
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| 137. |
What do you understand by the rate law and rate constant of a reaction? Identify the order of a reaction if the units of its rate constant are : |
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Answer» Rate Law: The way of expressing rate of reaction in terms of concentration of reactants. `eg: aA + bB tocC +dD` Rate `= k[A]^(lambda)[B]^(beta)` [`lambda,beta to` order of reacticve w.r.t of A and B respectively]. Rate constant: It is equal to the rate of reaction when molar concentraion of reaction is 1.Its unit depends upon the order of readion. (i) Zero order (ii) Second order. |
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| 138. |
Chlorofluorocarbons (CFCs) are widely used as refrigerants. Then why it is suggested to reduce its emission as far as possible ? Explain. |
| Answer» There is a delicate balance between production and degradation of ozone in the stratosphesre. The balance has been disrupted due to enhancement of ozone degradation by chlorofluorocarbons (CFCs). CFCs find wide use as refrigerants. CFCs discharged in the lower part of atmosphere move upward and reach stratosphere. In stratosphere, UV rays act on them releasing Cl atoms. Cl degrades ozone releasing molecular oxygen, with these atoms acting nearly as catalysts, Cl atoms are not consumed in the reaction. Hence, whatever CFCs are added to the stratosphere, they have permanent and continuing affects on Ozone Levels. | |
| 139. |
(a) What happens when : (i) HCl reacts with finely powdered iron. (ii) `Cl_(2)` reacts with hot concentrated solution of NaOH. (b) Give appropriate reason for each of the following : (i) Sulphur vapour exhibits some paramagnetic character. (ii) `NH_(3)` more basic than `PH_(3)`. (iii) Dioxygen is a gas but sulphur a solid. |
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Answer» (i) When HCl reacts with finely powdered iron, it forms ferrous chloride. `Fe+2HClrarrFeCl_(2)+H_(2)` (ii) `underset("(Conc.)")(3Cl_(2)+6NaOH)overset("Hot")rarrunderset("Sodium Chlorate")(5NaCl+NaClO_(3)+3H_(2)O)` (b) (i) In vapour state, sulphur partly exists as `S_(2)` molecules which has two unpaired electrons in the antibonding `pi^(**)`-molecular orbitals like `O_(2)` and hence, `S_(2)` exhibits paramagnetism. (ii) Due to the presence of a long pair of electrons on N and P, both `NH_(3)` and `PH_(3)` act as lewis bases and accept a proton to form an addition `N-H` and `P-H` bonds. However, due to smaller size of N over, P, N-H bond thus formed is much stronger than `P-H` bond. Therefore, `NH_(3)` has higher proton affinity than `PH_(3)`. (iii) Due to small size and high electronegativity, oxygen forms `ppi-ppi` multiple bonds. As a results, oxygen exists as `O_(2)` molecules which are held together by weak Van der Waals forces which can be easily overcome by collisions of molecules at room temperature. Hence, `O_(2)` is a gas at room temperature where as, sulphur has bigger size and lower electronegativity, does not form `ppi-ppi` multiple bond. Instead it prefers to form `S-S` single bond and has greater tendency for catenation and exist as `S_(8)` molecule. These molecules are held together by much stonger bond at room temperatrue. Hence, sulphur is a solid at room temperature. |
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| 140. |
A convex lens of focal length `f_(1)` is kept in contact with a concave lens of focal length `f_(2)`. Find the focal length of the combination. |
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Answer» For convex lens, focal length, `f = f_(1)` and for concave lens, the focal length, `f = -f_(2)`. The equivalent focal length of a combination of convex lens and concave lens is given as : `(1)/(F)=(1)/(f_(1))+(1)/(-f_(2))` `F = (f_(1)f_(2))/(f_(2)-f_(1))`. |
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| 141. |
(a) For a given a.c., `i = i_(m)` sin wt, show that the average power dissipated in a resistor R over a complete cycle is `(1)/(2) i._(m)^(2) R`. (b) A light bulb is rated at 100 W for a 220 V a.c. supply. Calculate the resistance of the bulb. |
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Answer» (a) The average power dissipated `bar(P)=(i^(2).R)=(i_(m)^(2)R sin^(2) omega t)=i_(m)^(2)R(sin^(2)omega t)` `therefore" "sin^(2)omega t=(1)/(2)(1-cos 2 omega t)" "=(sin^(2)omega t)=(1)/(2)(1-(cos 2 omega t))=(1)/(2)" "therefore" "(cos 2 omega t = 0)` `therefore" "bar(P)=(1)/(2)i_(m)^(2)R`. (b) Powet of the bulb, P = 100 W and voltage, V = 220 V. The resistance of the bulb is given as `R=(V^(2))/(P)=(220 xx 220)/(100)= 484 Omega`. |
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| 142. |
In the block diagram of a simple modulator for obtaining an AM signal, shown in the figure, identify the boxes A and B. Write their functions. |
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Answer» In the block diagram of modulator, A is square law device and B is band pass filter. Band pass filter rejects low and high frequencies and allows a band of frequencies to pass through. Square law device is a non linear device. It produces a non linear output of message and carrier signals. The output of square law device is, `y(t) = Bx(t) + Cx^(2)(t)` where B and C are constants and x(t) = message signal `(A_(m)sin omega_(m)t)` + carrier signal `(A_(c)sin omega_(c)t)` |
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| 143. |
A slab of materail of dielectric constant `K` has the same area as the plates of a parallel plate capacitor but has thickness `d//2`, where `d` is the separation between the plates. Find the expression for the capacitance when the slab is inserted between the plates. |
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Answer» Total potential difference between the plates `V = E_(0)(d-t)+Et" "(t=(d)/(2))` `V = E_(0)(d-(d)/(2))+E(d)/(2)" "E_(0)(d)/(2)+(E_(0))/(K).(d)/(2)=E_(0)(d)/(2)(1+(1)/(K))=E_(0)(q)/(A epsilon_(0))(d)/(2)(1+(1)/(K))` As, `C = (q)/(V)=(q)/((q)/(A epsilon_(0))(d)/(2)(1+(1)/(K)))=(2 A epsilon_(0))/(d(1+(1)/(K))) rArr C = (2 K epsilon_(0)A)/(d(K+1))`. |
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| 144. |
A parallel beam of light of 450 nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1.5 m away. It is observed that the first minimum is at a distance of 3 mm from the centre of the screen. Calculate the width of the slit. |
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Answer» The distance of the nth minimum from the centre of the screen, `x_(n)=(n D lambda)/(a)` Where D - distance `lambda` - wave length a - width of the slit For first minimum, `n=1, 3 xx 10^(-3)=(1 xx (1.5)xx(450 xx 10^(-9)))/(a)a=(1 xx (1.5)xx(450 xx 10^(-9)))/(3 xx 10^(-3))a=0.225 mm`. |
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| 145. |
(a) How are Parthenocarpic fruits produced by some plants and apomictic seeds by some others ? Explain. (b) When do farmers prefer using apomictic seeds ? |
| Answer» A commonly preserved non-sterdal oral pill is sachli. It is a once a week pill contraceptives value. | |
| 146. |
Why are some seeed refferred to as apomictic seeds ? Mention one adantage and one disadvantage to a farmer who uses them. |
| Answer» The development of sees without involving meiosis and fertilization is called apomixis .It is kind of asexual reproduction that miminc Sexual Reproduction .It is disadvantgeous because newer traits do not result in absence of sexual reproduction . | |
| 147. |
study the linking of DNA fragments shown above. (i) Name ‘a’ DNA and ‘1” DNA. (ii) Name the restriction enzyme that recognises this Palindrome, (iii) Name the enzyme that can link these two DNA fragments. |
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Answer» (i) a = Vector DNA or Plasmid DNA b = Foreign DNA (ii) The restriction enzyme is ECORI (iii) DNA Ligase. |
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| 148. |
Explain the imapct of removal of thymus gland on the immune system of a human body. |
| Answer» Thymus is a small, irregularly shaped gland situated just under breastbone and between the lungs. The thymus provided micro-environments for the development and maturation of T-lymphocytes. The T-cells themselves do not secrete antibodies but, they help B cells produce them. Therefore, the immunity will be reduced, if thymus is removed. | |
| 149. |
ATV tower has a height of 150m. By how much the height of tower be increased to double its coverage range ? |
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Answer» Here, `h = 150 m`, `d = sqrt(2 Rh) rArr d_(1) = 2d` `sqrt(2RH_(1)) = 2 sqrt(2Rh) rArr 2Rh_(1) = 4 (2Rh)` `h_(1) = 4h` `h = 4 xx 150 = 600 m` `:.` Increase in height of tower `= 600 - 150 = 450m` |
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| 150. |
A garden pea plant (A) Produceed inflated yellow pod, and another plant (B) of the same species produced constricted green pods. Identify the dominant traits. |
| Answer» Dominant traits are green and inflated. | |