InterviewSolution
Saved Bookmarks
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.
| 251. |
Which reducing agent is employed to get copper from the leached low-grade copper ore ? |
|
Answer» Copper can be obtained from low-grade ore through the process of leaching using acid or bacteria (leaching is a proces in which ore is treated with suitable reagent that dissolves ore but not impurities). The solution containing copper can be reduced with the help of reducing agents such as scrap iron or `H_(2)` to get copper metal. `Cu^(2+)(aq)+Fe to Cu (s) + Fe^(2+)(aq)` `Cu^(2+)(aq)+H_(2)(g) to Cu (s) + 3H^(+)(aq)` |
|
| 252. |
How would you account for the following : (i) Among lanthanoids , Ln(III) compounds are predominant , However, occasionally in solutions or in solid compounds , +2 and +4 ions are also obtained . (ii) The `E_(M2+//M)^(@)` for copper is positive (0.34V ) . Copper is the only metal in the first series of transition elements showing this behaviour . (iii) The metallic radii of the third (5d) series of transition metals are nearly the same as those of the corresponding members of the second series . |
|
Answer» `""_(58)Ce, _(59)Pr , _(60)Nd , _(65)Tb, _(66)Dy + 2 = _(60)Nd , _(62)Sm , _(63)Eu , _(69)Tm , _(70)Yb . +2` = oxidation state in exhibited when the lanthanoid has the configuration `5d^(@) 6s^(2)` so that 2 electrons are easily lost , +4 oxidations state is exhibited when the configuration left is close to `4f^(@)`(e.g.,`5f^(@), 4f^(1), 4f^(2)`) or close to `4f^(7)` (e.g., `4f^(7)` or `4f^(8)`). (ii) The `E_(M^(2+)//M)^(@)` for copper is positive (0.34V) . Copper is the only metal in the first series of the transition elements showing this behaviour . Due to its high enthalpy of atomisations and low hydration enthalpy . Hence high energy to transform Cu(S) to `Cu^(2+)` (aq) is not balanced by its hydration enthalpy (iii) The metallic radii of the third (5d) series of transition metals are nearly the same as those of the corresponding members of the second series because of lanthanoid contraction 4f orbital is filled before 5d due to that atomic radii decreases . Which compensates the expected increase in atomic size with increasing atomic numbers. |
|
| 253. |
Explain the following terms giving a suitable example for each : (i) Aerosol (ii) Emulsion (iii) Micelle |
| Answer» (ii) Emulsion : Emulsions are colloidal systems in which both the dispersed phase an dispersion medium are liquid . There are two type of emulsion such as , oil in water type emulsion , e.g., milk and water is oil type emulsion , e.g. , butter . | |
| 254. |
The reaction , `N_(2)(g) + O_(2) (g) hArr 2 NO(g)` contribute to air pollution whenever a fuel is burnt in air at a high temperature . At 1500 K , quilibrium constant K for its is `1.0 xx 10^(-5)` . Suppose in a case `[N_(2)] = 0.80 mol L^(-1)` and `[O_(2)] = 0.20 mol L^(-1)` before any reaction occurs . Calculate the equilibrium concentrations of the reactants and the product after the mixture has been heated to 1500 K. |
|
Answer» `N_(2)(g) + O_(2)(g) hArr 2NO(g) T = 1500 K K = 1.0 xx 10^(-5)` `{:([N_(2)]_(i) = 0.80 M [O_(2)] = 0.20 M " "N_(2) " "+ " "O_(2)hArr 2NO) , (t = O " "a " " b " "O), (t=t " "a-x " " b-x " "ax):}` `K = ([2x]^(2))/((a-x) (b-x))` `1.0 xx 10^(-5) = (4x^(2))/((0.80-x)(0.20 -x))` `4 xx 105 x^(2) + x - 0.16 = 0` Using quardratic formula `x = + 6.3 xx 10^(-4)` `therefore " "` [No]= `2x = 1.26 xx 10^(-3)M` `[N_(2)] = 0.80 - 6.3 xx 10^(-4) = 0.799M` `[O_(2)] = 0.20 - 6.3 xx 10^(-4) = 0.199 M` |
|
| 255. |
What are food preservatives ? Name two such substances . |
|
Answer» These are the chemical substances which are added to the food material to prevent food spoilage due to microbial growth the most commonly used preservative include table salt , vegetable oil , sugar , potassium metabisulphite and sodium benzoate. The most common preservations are sugar table , salt , sodium benzoate , propaoic acid. |
|
| 256. |
Where are fimbriae present in a human female reproductive system? Give their function. |
| Answer» The fimbriae are the finger-like projections present on the edge of infundibulum (fallopian tubes). They help in collection of ovum after ovulation | |
| 257. |
Banana is a parthenocarpic fruit where oranges show polyembryony. How are they different from each other with respect to seeds? |
| Answer» Banana develops from an ovary without fertilisation having non-viable seeds so it is called parthenocarpic fruit. An orange contain seeds with more than one embryo thus, it shows polyembryony | |
| 258. |
Name the organism commercially used for the production of single cell protein |
| Answer» Correct Answer - Spirulina | |
| 259. |
Mention the pollinating agent of an inflorescence of small dull coloured floweres with well exposed stamens and large feathery stigma. Give any one characteristic of pollen grains produced by such flowers. |
| Answer» Pollinating agent is wind. Pollen grains are light, dry and non-sticky. | |
| 260. |
Outline the principples behind the refining of metals by the following methods : (i) Zone refining method (ii)Chormatographaphic method |
|
Answer» (i) Zore refining Method : Zone refining method is based on the principle that impurities are more soluble in the molten state then in the solid state of a metal. This method is used in the purification of elements like Germanium (Ge), Silicon (Si), Indium (In) etc. (ii) Chromatography method : Chromatography is the technique used for separation of the compoenents of a mixture that are soluble in the same solvent and are differently adsorbed on an adsorbent. This teachnique was first used for separation of colurs and hence, the name. There are two phases in chromatography - the stationary phase and the mobile phase. The components of the mixture are absorbed differently in the stationary phase, thus leading to their separation. There are many different types of chromatography-paper chromatography, thin-layar chromatography, gas chromatography etc. |
|
| 261. |
(a) Why are the fruit juices brought from market clearer as compared to those made at home? (b) Name the bioactive molecule produced by Trichoderma polysporum. |
|
Answer» (a) The fruit juices available in the market are made clarified by treating them with the enzymes- pectinases and proteases. So, they are clearer as compare to those made at home. (b) Trichoderma polysporum is used to produce immuno suppressive agent cyclosporine A. Monascus purpureus is used to produce blood-cholesterol lowering agents statins. |
|
| 262. |
(i) Deficiency of which vitamin causes night-blindness ? (ii) Name the base that is found in nucleotide of RNA only. (iii) Glucose on reaction with HI gives n-hexane. What does it suggest about the structure of glucose ? |
|
Answer» (i) Night blindness is caused due to the deficiency c. vitamin A. Uracil is the base that is found only in the nucleotide of RNA. (iii) The reaction of glucose with HI giving n-hexane suggests that all the six carbon atoms are linked in a straight chain, as shown in the reaction given below : `CHO-(CHOH)_(4)-CG_(2)OH+HI overset DeltatoCH_(3)-CH_(2)-CH_(2)-CH_(2)-CH_(2)-CH_(2)` |
|
| 263. |
Mention the target cells of luteinising hormone in human males and females. Explain the effect and the changes which the hormone induces in each case. |
| Answer» The target sells ofluteinsing hormone in males are the leydig ceHs and in females are the mature growing follicles LH in males stimulates the leydig cells of tests to synthesise and secrete Androgens which in turn stimulate the process of spermatogenesis .LH in femalales stimulatethe otimulate the ovulation, transformation of graafian follicle into corpus luteum to secrete progesterone which prepares the endometrium to receive and implant blastocyst | |
| 264. |
Draw the microscopic structure of human sperm and relate its different parts with their functions. |
| Answer» See Q.19. Set-I., Delhi Board-2008. | |
| 265. |
(a) Draw the longitudinal section of a flower showing growth of pollen tube upto the embryo sac.Label the following parts : (i) Stigma (ii) Pollen tube (iii) Integument (iv) Chalazal end (v) Nucelllus (vi) Synergids (b) What is double fertilisation in Angiosperms? Why is it so called ? |
|
Answer» (a) See Q.29, Set-II.., Outside Delhi-2014 (Comptt.) [Page-245]. (b) The second male gamete moves towards the polar nuclei in the central cell and fuses with them the produce a triploid primary endosperm nucleous. Since syngamy and triple fusion occur in the embryo sec. The process is called double fertilisation. |
|
| 266. |
Explain the following phases in the menstrual cycle of a human female : (i) Menstrual phase (ii) Follicular phase (iii) Luteal phase |
|
Answer» (a) (i) The cycle starts with the menstrual phase when menstrual flow occurs and its losts for 3-5 days . The menstrual flow results due to break down of endometrial lining of the uterus and its blood vessels which forms liquid that comes out through vagina. (ii) The menestrual phase is followed by the follicular phase. During this phase , the primary follicles in the ovary grown to become a fully mature graffian follicle and simutaneusely the endometrium of uterus regenerates through proliferation . the secretion of gonadotropins increase gradually during the follicule phase and stimulates follicular development as well as secretion of estrogens by the growing follicles. (iii) Luteal phase during which the remairing part of the graffian follicle transfrom as the corpus luteum . the corpus luteum secretes large amounts of progesterone which is essential for maintenance of the endometrium. |
|
| 267. |
Explain the following phases in the menstrual cycle of a human female : (i) Menstrual phase (ii) Follicular phase (iii) Luteal phase |
|
Answer» (a) (i) The cycle starts with the menstrual phase when menstrual flow occurs and its losts for 3-5 days . The menstrual flow results due to break down of endometrial lining of the uterus and its blood vessels which forms liquid that comes out through vagina. (ii) The menestrual phase is followed by the follicular phase. During this phase , the primary follicles in the ovary grown to become a fully mature graffian follicle and simutaneusely the endometrium of uterus regenerates through proliferation . the secretion of gonadotropins increase gradually during the follicule phase and stimulates follicular development as well as secretion of estrogens by the growing follicles. (iii) Luteal phase during which the remairing part of the graffian follicle transfrom as the corpus luteum . the corpus luteum secretes large amounts of progesterone which is essential for maintenance of the endometrium. |
|
| 268. |
(a) Compare , giving reasons , the J- shaped and S- shaped models of population growth of a species. (b) Explain " fitness of a species " as mentioned by Darwin. |
|
Answer» (a) J- shaped - When the responses are not limiting the growth plot is exponential. Darwin showed how even a slow growing animals like elephant could reach enormous numbers in the absence of checks. dN/dt =rN The above equation describes the exponential or geometric growth pattern of a population and results in J- shaped curve. `dN//dt=rN((K-N)/(K))` where, N= population density at time t. r= intrinsic rate of natural increase. K= carrying capacity. (b) When Darwin spoke of the struggle for existence and survival of the fittest in nature . He was cominced convinced that interspecific competition occurs when closely related species compete for same resource that are limiting but this is entively not true. (1) Unrelated species could also compete for the same . For example . in some shallow South American lakes visiting flamingoes and resident fishes compete for their common food, the zooplankton in the lake. (2) Resources need not to be limiting for competition to occur in interference. |
|
| 269. |
(a) Write the formula and describe the structure of a noble gas species which is isostructural with (i) `"Ibr"_(2)^(-)` (ii) `BrO_(3)^(-)` (b) Assign reasons for the following : (i) `SF_(6)` is kinetically inert. (ii) `NF_(3)` is an exothermic compound whereas `NCl_(3)` is not. (iii) HCl is a stronger acid than HF though fluorine is more electronegative than chlorine. |
|
Answer» (a) (i) `XeF_(2)`=liner (ii) `XeO_(3)` =Pyramidal (b) (i) Because sulphur is stericoly protected by six Fatoms. (iii) H-X bond length increases for HCl, bond dissociation energy decreases. Hence HCl is strong acid than HF |
|
| 270. |
Write the equations for the preparation of 1-bromobutane from : `(i) "1-butanol"" "(ii)"but -1-ene"` |
|
Answer» (i) Butanol `to` bromobutane `CH_(3)CH_(2)CH_(2)CH_(2)OHoverset(SOCl_(2))toCH_(3)CH_(2)CH_(2)CH_(2)Cl` (ii) But -1-ene `to` Brombutane `CH_(3)CH_(2)CH_(2)CH_(2)+HBroverset("Peroxide")toCH_(3)CH_(2)CH_(2)CH_(2)Br` |
|
| 271. |
Find the value of `lambda` , if four points with position vectors `3 hati + 6 hatj + 9 hatk, hati + 2 hatj + 3 hatk, 2 hati + 3 hatj + hatk and 4 hati + 6 hatj + lambdahat k` are coplanar. |
|
Answer» `AB=(-2,-4,-6)`, .`AC=(-1,-3,-8)` `AD=(1,0,lambda-9)` As, all these vectors are coplanar, So`|(-2,-4,-6), (-1.-3,-8),(1,0,lambda-9)|=0`Hence,`Lambda=2` |
|
| 272. |
If A is a skew-symmetric matrix of order 3, then prove that det `A = 0`. |
|
Answer» `A^T=-A` as A is a skew symmetric matrix. `|A|=|A^T|` `|A|=|-A|=-|A|` `2|A|=0` `|A|=0` |
|
| 273. |
A criminal blew himself up in a local market when was chased by cops. His face was beyond recognition. Suggest and describes a modern technique that can help establish his identity? |
|
Answer» The technique of DNA Finger printing was initially deveoped by Alec Jeffreys. He used to satellite DNA as probe that shows very high of polymorphism. It was calle as Variable Number of Tandem Repeats (VNTR). The technique as used earlier, involved Southern blot hybridisation using radiolabelled VNTR as a probe. It included: i) Isolation of DNA ii) digestion of DNA by restriction endonucleases. iii) separation of DNA fragments by electrophoresis |
|
| 274. |
A number of passengers were severely burnt beyond recognition during a train accident. Name and describe a modern technique that can help hand over the dead to their relatives. |
| Answer» A modern technique that can help in DNA fingerprinting. The technique of DNA fingerprinting was initially developed by Alec Jeffreys. He used a satellite DNA as probe the shows very high degree of polymophism. It was called as Veriable Number of Tandem Repeat (VNTR). The VNTR belongs to a class of satellite. DNA referred as a mini satellite since DNA same degree of polymorphism, they become use tool in forensic applications. | |
| 275. |
Following the collision of two trains a large number of passengers are killed A majority of them are beyond recognition .Authorities want to hand over the dead to their relatives .Name a modern scientific method and write the procedure that would hepl in the identification of kinship . |
| Answer» Dna fingerpriting is the modern scientific menthod used for the identificaion of kinship | |
| 276. |
How do monocytes act as a cellular barrier in humans to provide innate immunity ? |
| Answer» Monocytes are mononuclear phagocytic leucocytes that cirulate briefly in the blood stream before migrating into the tissues where it becomes macrophages or into dendritic cells. They protect against infections, kills micro-organisms, ingest foreign particles , remove dead cells and boost immune system. | |
| 277. |
Why is the structure of an antibody molecule represented as `H_(2)L_(2)` ? Name any two types of antibodies produced in a human body. |
| Answer» Human antibodies or immunoglobulins are designated as `H_(2)L_(2)` as they have w heavy chains and 2 light chains. An antibody is a Y-shaped structure. `IgCr` and `IgA` antibodies are produced in a human body. | |
| 278. |
You are conducting artificial hybridization on papaya and potato. Which one of them would require the step of emasculation and why? However for both you will use the process of bagging. Justify giving one reason. |
|
Answer» Potato plant require the step of emasculation, papaya plant do not because potato is a monoecious (hermaphrodite) and papaya is dioecious. However, for both flowers bagging is required to avoid undesired pollination because of insects or air. |
|
| 279. |
(a) How many codons code for amino acids and how many are unable to do so ? (b) Why are codes said to be (i) degenerate and (ii)unambigous ? |
|
Answer» 61 codons code for amino acids and 3 are unable to do so. See Q.29 (or) (b), Set III, outside Delhi 2008. |
|
| 280. |
What did Meselson and Stahl observe when They cultured E. coli in a medium containing `""^15Nh_4CL` for a few generations and centrifuged the content? they transferred one such bacterium to the normal medium of `NH_4Cl` and cultured for 2 genretion ? What did Meselson and Stahl conclude from this experiment? Explain With the help of diagram Which is the first geretic material? Give reasons in support of your answer. |
|
Answer» Meselson and Stahl obsered that in the E. coli bacterium the DNA becomes completely labelled with `N^15` medium by centrifugation for few genretion ·After two genretion density changed and showed equal amount of light DNA(`N^14`) and dark hybrid DNA `(N^14-N^15)`. They concluded that DNA replicates semi-conservately.[For Figure See Q. 30. Set-I. Outside Delhi, 2008]. .RNA is the first genetic material. RNA is highly reactive, and acts as a catalyst as well as genetic material. Essential life processes such as metabolism, translation and splicing evolved around RNA. |
|
| 281. |
(a) Write the fate of egg cell and polar nuclei after fertilization. |
|
Answer» (a) When the pollen grains falls on the stigma, the pollen tube enters one of the synergids and releases two male gametes. (i) One of the male gametes moves towards the egg cell and fuses with it to complete syngamy to form the zygote. (ii) The other male gamete fuses with the two polar nuclei and forms triploid primary endosperm nucleus (PEN). This is termed as triple fusion. (iii) Since two kinds of fusion-syngamy and triple fusion-takes place, the process is known as double fertilisation and is chracteristic of flowering plants. |
|
| 282. |
Name an IUD that you would recommend to promote the cervix hostility to the sperms. |
| Answer» Correct Answer - Progestasert/LNg20 | |
| 283. |
(i) Why are grasshopper and Drosophila said to show male heterogamity ? Explain. (ii) Explain female heterogamity with the help of an example. |
|
Answer» (i) Drosophilia exhibit XY type of sex determination. Males produce two types of sperms, one having X chromosome and one having Y chromosome. Whereas females have only X-type of chromosomes. Grasshoppers exhibit XO type of sex determination. Males produce two types of gametes, one with X chromosome and other with no chromosome. Thus, both show male heterogamety. (ii) Female heterogamety can be seen in female birds. In these, the females have one Z and one W chromosome whereas males have a pair of Z-chromosomes beside the autosomes. |
|
| 284. |
"Intra-cytoplasmic sperm injection" and "Gamete intra fallopian transfer" are two assisted reproductive technologies. How is one different from the other ? |
| Answer» In Intra-cytoplasmic sperm injection sperm is drectly injected into the ovum in the laboratory. In gamete intrafallopian transfer ovum is callected from a donor and transferred into the fallopian tube of surrogate mother. | |
| 285. |
A person in your colony has recently been diagnosed with AIDS. People/residents in the colony want him to leave the colony for the fear of spread of AIDS. a) Write your view on the situation, giving reasons. b) List the possible preventive measures that you would suggest to the residents of your locality in a meeting organised by you so that they understand the situation. c) Write the symptoms and the causative agents of AIDS. |
|
Answer» a) Recently by chance, AIDS is diagonosed in our area. It is fatal disease. We should create awareness among the people to combat such situation and not to isolate the AIDS infected person from the society. b) It is important that HIV/AIDS is not spread by more touch or physical contact, it spreads only through body fluids. It is, hence, imperative, for the physical and psychological well being, that the HIV/AIDS infected persons are not isolated from family and society. c) AIDS is caused by the Human Immuno deficiency Virus (HIV), a member of a group of viruses called retrovirus. Transmission of HIV-infection generally occurs due to: a) Sexual contact with an infected person. b) by transfusion of contaminated blood and blood products. c) by sharing infected needles as in the case of intravenous drug abusers. d) from infected mother to her child through Placenta. Symptoms of AIDS: HIV-AIDS is characterized by a decrease in T-helper (T-H) lymphocytes. The patient suffers bouts of fever, diarrhea and weight loss. Due to decrease in the number of T-helper lymphocytes, the person starts suffering from opportunistic infections like, mycobacterial infections, toxoplasmosis, fungi and virsues. |
|
| 286. |
Account for the following (i) Reducing character decreases from `SO_(2)` to `TeO_(2).` (ii) `HClO_(3)` is a stronger acid than HClO. (iii) Xenon forms compounds with fluorine and ozygen only. (b) Complete the following equations : (i) `4NaCl+MnO_(2)+4H_(2)SO_(4)to` (ii) `6XeF_(4)+12H_(2)Oto` |
|
Answer» (a) (i) Since +6 oxidiation state of S is more stable than +4, therefore, `SO_(2)` act as a reducing agent. Since the stability of +6 oxidatin decreases from S to Te, therfore, reducing character decreases from `SO_(2)` to `TeI_(2).` (ii) `overset(+5)(HClO_(3)),overset(+1)(HClO)` Greater the number of oxygen atoms in anion (formed by the removal of Hydrogen ) greater will be the dispersal of negative charge through p `pi-d pi` back bonding and hence greater will be the stability of anions, greater will be the acidity. Hence `HClO_(3)` is stronger acid than HClO. (iii) Fluorine and oxygen are the most electronegative elements and hence are very reactive. Therefore, Xenon forms compounds with flurine and oxygen only. (b) (i) `4NaCl+MnO_(2)+4H_(2)SO_(4)to MnCl_(2)+4NaHSO_(4)+2H_(2)O+Cl_(2)` (ii) `6XeF_(4)+12H_(2)O to4Xe+2XeO_(3)+24HF+3O_(2)` |
|
| 287. |
Write the reaticon involved in the Hoffmann bromamide degradation raction . |
| Answer» `RCONH_2+Br_2+4NaOH rarr R-NH_2+Na_2CO_3+2NaBr+2H_2O` | |
| 288. |
Name the type of evolution that has redulted in the development of structures like wings of butterfly and bird. What are such structures called ? |
| Answer» Convergent evolution. | |
| 289. |
Explain commensalism, with the help of an example. |
| Answer» Commensalism - commensalism is an interaction in which smaller partner, called commensal, is benefitted while the large partner, called host, is neither benefitted nor harmed e.g. orchids as epiphytes on a mango branch. | |
| 290. |
These pictrues show the gynaeceum of (A) Papaver and (B) Michellia flowers. Write the difference in the structure of their ovaries. |
| Answer» In Papaver the gynaecium is multicarpellary, syncarpous. While in Michelia flower the gynoecium is multicarpellary, apocarpous. | |
| 291. |
(a) What are the after effects of the degradation of ozone ? (b) How does it affect human health ? |
|
Answer» (a) Effects of degradation of ozone : (1) UV-B damages DNA and proteins of living organisms causing mutation. (2) It causes skin ageing, skin cell damage and skin cancer. (b) CFCs release active chlorine which react with UV rays and degrade ozone releasing molecular oxygen. Depletion of ozone allows the entry of UV-B radiation to the earth which damages DNA causes mutation leading to the skin cancer in human and also rate of photosynthesis decreases in plants. |
|
| 292. |
Our farmers still use DDt. How is the affecting the local bird population ? |
|
Answer» Our farmers still use DDT. Mercury and DDT are well known for biological magnification. Calcium metabolism in birds is disturbed which results in thinning of egg shell. This leads to decline in birds population. If DDT leaches from the agricultural field, it gets into the water body (the concentration is 0.0003 ppm) and enters the food chain: zooplanktons (0.4ppm)-small fish (0.05ppm)-large fish (2ppm)- any fish eating birds (5ppm). Concentration of DDT increases along the food chain, reaching a high level in the top carnivore bird. DDT concentration disturbs `Ca^(++)` metabolism, egg shells become thin, premature breaking resulting in decline in bird population. |
|
| 293. |
Name the enzyme that transcribes hnRNA in eukaryotes. |
| Answer» The RNA polymerase II transcribes precursor of mRNA, the heterogeneous nuclear RNA (hnRNA). | |
| 294. |
Give an example of a plant which came into India as a contaminant and is a cause of pollen allergy. |
| Answer» Pollen grains of many species cause servere allergies and bronchial conditions such as carrot grass that came into India as a contaminant with imported wheat. | |
| 295. |
(i) Write two characteristics of a material used for making permanaent magnets. (ii) Why is core of an electromagnet made of ferromagnetic materials ? |
|
Answer» (i) The materials chosen to make permanent magnets should have (ii) High retentivity so that the magnet is strong. (b) High permeability so that the magnet can be magnetished easily. (i) The core of electromagnets are made of ferromagnetic materials, which have high permeability and low retentivity. Soft iron is a suitable material for this purpose. |
|
| 296. |
Answer the following : (a) Why are the connections between the resistors in a meter bridge made of thick copper strips? (b) Why is it generally preferred to obtain the balance point in the middle of the meter bridge wire? ( c) Which material is used for the meter bridge wire and why? |
|
Answer» (a) The resistivity of a copper wire of very low. Also, the connections are thick, so that the area is quite large and hence the resistance of the wire is almost negligible. (b) It is preffered to obtain the balance point in the middle of the meter bridge wire because it improves the sensitivity of the meter bridge. (c) Constantan is used for meter bridge wire because its temperature coefficient of resistance is almost negligible due to which the increase in temperature of the wire due to flow of current. |
|
| 297. |
A coil, of areas A, carrying a steady current I, has a magnetic moment, `vecm`, associated with it. Write the relation, between `vecm`, I am A in vector form. |
| Answer» Correct Answer - `vecm=Ivecm` | |
| 298. |
Ravi is a student of mechanical engineering studying in one of the engineering colleges. The other day he saw an old man who suddenly collapsed as he walked out of the house in his neighbourhood. Ravi the emergency ward of the hospital. On getting the medical aid, the old man soon goy recovered. He did not forget to thank Ravi for the timely help he rendered. He was wondering that in his times to get the telephone connection. One had to wait for years whereas these days it takes no time to get the connection. Ravi told him it was all because of the technological progress/deveolpement due to which the simple phenomenon in physics could be easily used. Answer the following questions based on the above : (a) To which phenomenon in physics was Ravi referring to, which made the land line links so easily accessible? (b) What are the essential conditions required to observe this phenomenon ? (c) Write two values displayed by Ravi and the old man in this episode. |
|
Answer» (a) (i) Total internal reflection. (b)(i) Light should go from denser mdeium to rarer medium. (ii) Angle of incidence should be greaterf than critical angle. (c) Values displayed by Ravi (i) Helpful (helping attitude),(ii) Knows how to use modern technology. By old man : (i) Thankful , (ii) Surprised to see changes in technology. |
|
| 299. |
The following data was obtained for a given transistor: For the data, calcalate the input resistance of the given transistor. |
|
Answer» Input resistance `=(DeltaV_(BE))/(DeltaI_(B))=(0.82-0.72)/((80-30)xx10^(-6))=(.10)/(50xx10^(-6))=(10xx10^(-2)xx10)/(50)` `=(100000)/(50)=2000Omega`. |
|
| 300. |
A proton and alpha particle are accelerated through the same accelerating potential. Which one of the two has (a) greater value of de-broglie wavelength associated with it, and (b) less kinetic energy? justify your answer. |
|
Answer» (a) De-Broglie wavelenth of a particle depends upon its mass and chargbe for same accelerating potential, such that `lambda prop (1)/(sqrt("mass"xx "charge")` Mass and charge of a deuteron are `2m_(rho)and e` respectively and mass and charge of an alpha particle are `4m^(rho)` and 2e respectively. Where, `m_(rho)` is the mass of a proton and e is the charge of an electron. `(lambda_(d))/(lambda_(prop))=(sqrt(4mp.2e))/(sqrt(2mp.e))=2` `rArr" "lambda_(d)=2lambda_(prop)`. |
|