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CSIR UGC NET, 2012 June 17, Question Paper, Download, Answer Key, Answers, solutions, Explanations, Comment Here

► CSIR UGC NET, 2012 June 17, Question Paper, Download, Answer Key, Answers, solutions, Explanations, Comment Here

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UGC CSIR NET 2012 June 17 Answer Key Comment here with explanation
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250 comments :

  1. Anonymous17 June, 2012

    comment the questions from your memory to construct full question paper.

    ReplyDelete
    Replies
    1. Anonymous18 June, 2012

      Which of the following would be the possible blood of child if the parents have O and AB blood groups?

      Ans: A and B

      Delete
    2. Anonymous19 June, 2012

      it should be A or B. NOT O

      Delete
    3. Anonymous19 June, 2012

      A and B is correct. A and O is possible only when parents have a combination of A & O. Refer Surekha Tomar's guide on Physical sciences.

      Delete
    4. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : A , B BLOOD GROUPS

      Delete
  2. Anonymous17 June, 2012

    d' < 2d

    ReplyDelete
    Replies
    1. since force*distance is constant. therefore it should be d=2d'

      Delete
    2. @Raja you are wrong look question no 100 at100 Questions

      Delete
    3. Anonymous19 June, 2012

      Since the force is force perpendicular to the rod d=2d' is valid( here rod weight is negligible). In the 100th question (you prescribed) rod weight is not negligible.It is comparable to the wight of hanging body. So I d=2d' is correct answer in general question.

      Delete
    4. @SREEJITH P
      raja is correct, its just balance of moments (torque) about the point of support which easily gives d=2d'.

      Delete
    5. In the question it is a bar. Then it can be consider the mass. If mass is not considering the answer as per Raja.
      If we consider the mass of the bar, ?

      Delete
    6. the mass of rod was not given in the question...........so we cann't consider the mass.

      Delete
    7. In the question it is a bar. for a bar there will be a thickness and width. Also in the figure it shown as a thick line (not a thin line). so we need to consider the mass of the bar. d=2d' is an approximation. we need to select more accurate answer.
      please reply ..

      Delete
    8. however in ques mass was not given but it was mentioned that bar is not massless but of uniform mass/length.

      Delete
  3. eigen value of matrix [1 2 3;2,4,6;3,6,9] is 0,0,14,

    ReplyDelete
    Replies
    1. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      MATRIX 1 2 3
      2 4 6
      3 6 9

      CORRECT ANSWER : 0,0,14 are the correct eigen values

      Delete
  4. Anonymous18 June, 2012

    weight is same
    slope 1<m<root3

    paper was very very tough

    ReplyDelete
  5. Anonymous18 June, 2012

    person in center of disc rotating with angular momentum Omega(in up direction)- 2v*Omega to his left
    S is proportional to T^3. So entropy increases 8 times
    Digital electronics question- output in both cases is 1 (1,1)
    Dominant multipolarity - E2 and M3

    ReplyDelete
    Replies
    1. for angular momentum question direction of rotation is not specified,so data is insufficient.

      Delete
    2. Omega was given vertically upward so disc was rotating anticlockwise as seen from above the disc.

      Delete
    3. can u plz explain the question dominant multipolarity.. i didnt get it

      Delete
  6. Anonymous18 June, 2012

    i heard that questions in part c was so tough and most of them are from advanced topics

    ReplyDelete
  7. shyam sundar pareek18 June, 2012

    answer to question lorentz invarients is Esquare2Bsqaure2.

    op-amp output volate is -1volt

    in h parameter ans is voltage gain is 35 and curret gain is -35

    ReplyDelete
    Replies
    1. Anonymous18 June, 2012

      no shyam if you will see Irodo's book of electromagnetism ,there it is wriiten that E^2 -c^2b^2 is lorentz invariant.

      Delete
    2. Mr shyam for your third ans i want to tell you that voltage gain for CE configu
      -tion is always negative thats why ans should be -35, and current gain is 35

      Delete
    3. it is also correct,

      Delete
    4. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : E^2 * B^2 is lorentz invariant

      Delete
  8. PhotoSynthesis is more on the sea level compare with high altitude.

    The rate of photosynthesis increases as the humidity increases.

    ReplyDelete
    Replies
    1. why??plz explain...why not pressure?

      Delete
    2. Anonymous19 June, 2012

      because photosynthesis depends on atmospheric CO2 and H2O . concentration of both are high at sea level.

      Delete
    3. Why only the humidity and the pressure factor is there ? The intensity may play the factor in case of grwth . .. .

      Delete
    4. Anonymous19 June, 2012

      Is it not intensity of light which is more at see level?

      Delete
    5. http://fhs-bio-wiki.pbworks.com/w/page/12145771/Factors%20effecting%20the%20rate%20of%20photosynthesis

      Friends, go through this for better understanding on photosynthesis

      Delete
    6. Anonymous23 June, 2012

      The right answer is pressure. The pressure at sea level is high... due to which the density of air is high. It means the number of CO2 molecules per unit volume of air is more. So the CO2 uptake will be more and hence the rate of photosynthesis.Hope itz the answer of the question.

      Delete
  9. Anonymous18 June, 2012

    What about the velocity time graph

    ReplyDelete
    Replies
    1. Anonymous18 June, 2012

      straight line

      Delete
    2. Anonymous18 June, 2012

      option a

      Delete
    3. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : straight line graph

      Delete
    4. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : straight line graph with negative slope is the correct answer to the velocity time graph

      Delete
  10. Anonymous18 June, 2012

    part A maths (1) ratio of population B to A is 1.44 (2) perimeter of triangle is 47.32 (3) area of shaded portion is pi-2 (4) angle of semi circle <APB=<AQB (5) figure suggest that (a+b)2=a2 + b2 +2ab (6) ice melts due to shoes presure of sketer ans is first

    ReplyDelete
    Replies
    1. @ anonymous...perimeter is 40
      i think the question was the sides of a right angled triangle are in AP . its smallest side is 10cm then calculate its perimeter?

      Delete
    2. angles are in AP or sides are in AP ????

      Delete
  11. opamp ans -1
    digital electronics ans 111

    ReplyDelete
  12. Replies
    1. Anonymous19 June, 2012

      17 is correct. I myself could count 16 and there was no option with 16 and hence can't be less than 16.

      Delete
    2. Anonymous21 June, 2012

      They are asking for squares , not rectangles, Still can we count 17 ?

      Delete
    3. Anonymous25 June, 2012

      Yes 17 are there

      Delete
    4. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : 15 squares

      EXPLANATION : number of small squares = 9
      number of squares with sides twice that of small squares = 5 (one common is redundent)
      number of squares with sides three times that of small squares = 1
      therefore total number of squares = 9 + 5 + 1 = 15

      Delete
  13. Anonymous18 June, 2012

    gypsum-plaster of paris
    porcelain- clay
    limestone-cement
    silica sand- glass

    ReplyDelete
    Replies
    1. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      above mentioned matches are absolutely correct

      Delete
  14. How many square was there?

    ReplyDelete
    Replies
    1. total no. of square is 17

      Delete
    2. Anonymous19 June, 2012

      No Bist that will be wrong answer. The right answer is 15 squares...

      Delete
  15. [ X2,P2] = ?


    Ans: 2ih[px+xp]

    ReplyDelete
    Replies
    1. Anonymous18 June, 2012

      it should be 2ihxp

      Delete
    2. This comment has been removed by the author.

      Delete
    3. Anonymous18 June, 2012

      @MUTHU is correct

      Delete
    4. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : 2i(h/2pi)[px=xp]

      Delete
  16. Anonymous18 June, 2012

    output of digital circuit (1,1)

    ReplyDelete
    Replies
    1. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT

      Delete
  17. Anonymous18 June, 2012

    weight is equal of both jar A and B

    ReplyDelete
  18. opamp output should be -0.5 V becoz there is voltage divider at the output with equal resistance so the output will be half.

    ReplyDelete
    Replies
    1. ravi kumar g raj nair absolutely right

      Delete
    2. Anonymous23 June, 2012

      nair g
      for that question
      ans is -1 v
      bcz in parallel voltage remain same

      Delete
    3. Anonymous24 June, 2012

      we can solve the ckt using th econcept of kirchoff's law.Then we get answer is -1 V

      Delete
  19. Anonymous18 June, 2012

    In velocity time graph, option (a) was correct because in that fig slope was negative (use this formula v=u-gt)

    ReplyDelete
  20. Anonymous18 June, 2012

    Part C: Eigen values of antisymmetric matrix
    Ans: 0, i, -i

    ReplyDelete
    Replies
    1. Anonymous20 June, 2012

      wrong. ryt ans is 0,0,0

      Delete
    2. Anonymous23 June, 2012

      mr anonymous
      correct ans is:0,i -i as calculated
      bcz jaruri nahi ke antisymm matrix ki e.v.sirf zero ho
      they may be imaginary

      Delete
    3. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      MATRIX : 0 L M
      -L 0 N
      -M -N 0

      where L, M, N are the components of a unit vector

      CORRECT ANSWER : o, i and -i

      Delete
  21. Anonymous18 June, 2012

    0, -i, i correct

    ReplyDelete
  22. What abt d ans of qs..in jet chewing gum helps us?

    ReplyDelete
    Replies
    1. Anonymous18 June, 2012

      pressure balances
      Chew gum. Chewing gum stretches muscles in the jaw and throat that can cause the eustachian tubes to open. This allows air into the middle ear and equalizes the pressure. Keep chewing gum as long as the pressure is changing.

      Delete
    2. Anonymous18 June, 2012

      maintenance of pressure on both the sides of the person who chewings the chewing gum.

      Delete
    3. Anonymous20 June, 2012

      pressure balance is the right answer..

      Delete
  23. ALL PHYSICS STUDENTS COME HERE.. WE RECONSTRUCT THE PAPER. FIRST LET US RECOLLECT 20 QUESTIONS.
    1. WEIGHT OF TWO JARS QUESTION
    2. BLOOD GROUP OF CHILDREN FOR O-AB
    3. VELOCITY GRAPH
    4. PRESSURE ON EAR DRUMS
    5. Y NT SOLAR ECLIPSE ON EACH FULL MOON DAY
    6. PHOTOSYNTHESIS N ALTITUDE RELATION
    7. AVERAGE SLOPE OF LINE
    8. INCENSE STICK SMELL SPREADS FASTER IN H/L ALTITUDE AND H/L TEMP
    9. SEISMIC FOCUS OF S-WAVE N P-WAVE
    10. SATURATED SOLUTION PREPARATION OF SUGAR ---- GRAPH
    11. AA' AT EQUATOR N BB' AT 60* WTS D RELATION

    COMMON FRNDS COMPLETE THE REMAINING 9 QUESTIONS THEN VL DISCUSS ANS

    ReplyDelete
    Replies
    1. 12. MASS OF SAND PILE AS FUNCTION OF HEIGHT
      13.CARBON DATING
      14.NUMBER of SQUARES

      Delete
    2. ratio of daughter parent nuclei after 2 half lifes

      Delete
    3. Ratio of daugter parent nuclei after 2 half lifes is 3.

      Delete
    4. Suppose any number of nuclei e.g. 1500, (one can take any number instead 1500).
      After one half life: No. of parent nuclei left= No. of daughter nuclei formed= 750
      and after one more half life No. of parent nuclei left = 750/2 = 375
      and No. of daughter nuclei formed = 375 + 750(previous one) = 1125,

      So the ratio is 1125/375=3

      Delete
    5. In the sand pile question there is a word "pile of same geometry" ...
      then , is it mean if the height increase the width also increase? please comment...

      Delete
    6. Same geometry refers that
      1/3*pi*r1^2*h1 : 1/3*pi*r2^2*h2
      therefore h1:h2 = r2^2:r1^2. correct?

      Delete
    7. that is ratio of volume = ratio of the cube of height..

      Delete
    8. Anonymous20 June, 2012

      itz mentioned only about height.so no consideration is given to radius

      Delete
  24. Frpm Part A regarding carbon dating

    Because the half-life of carbon-14 is 5,700 years, it is only reliable for dating objects up to about 60,000 years old.

    So the answer is that the c-14 would have all decayed (dont remember which option -i think D )

    ReplyDelete
    Replies
    1. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : Almost all of the C-14 atoms would have decayed

      Delete
  25. although CO2 concentration is same in the atmosphere, give reason why rate of photo synthesis is more in the surface as compared to higher altitude?

    ReplyDelete
    Replies
    1. Can you see in top? already, it is there.

      Delete
  26. the reaction between hadron, leptons and decay are strong, electromagnetic and weak....

    ReplyDelete
  27. IF two different sizes of sand are kept with same height, then volume will be proportional to.....

    ReplyDelete
  28. a match stick is burnt then where it will smelt quickly...at surface or at higher altitude?

    ReplyDelete
    Replies
    1. Temperature is responsible to spread some quantity, depends on density also. so surface.

      Delete
  29. N bosons has to place in two different energy levels...how many ways u can place them?

    ReplyDelete
    Replies
    1. Anonymous20 June, 2012

      is it sure

      Delete
    2. the bosons are identical.

      If number of bosons are two, then the possible ways are, (1)two bosons in 1st state, (2)two bosons in 2nd state (3)one in 1st another in 2nd. Hence possible ways 3.

      If number of bosons are three, (1)three are in 1st state (2) two in 1st state, one in 2nd state (3)one in 1st state, other two in 2nd state (4)three are in 2nd state . Hence possible ways 4.

      If number of bosons are four, (1)four in 1st state (2) 3 in 1st state, 1 in 2nd state (3)2 in 1st state, 2 in 2nd state (4) 1 in 1st state 3 in 2nd state (5)all in 2nd state. Hence possible ways 5.

      and so on...

      Is it correct??!

      Delete
    3. Anonymous22 June, 2012

      i would like to know the explanation behind this answer...

      Delete
    4. @Vijay I did the same way you explained by taking diff values for N.The answer is correct there r N+1 ways.

      check out this wiki page - http://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_statistics

      From that page - "It is easy to see that there are (n+1) ways of distributing n particles in two sublevels..........."

      Delete
    5. This comment has been removed by the author.

      Delete
    6. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : N+1 ways
      @Vijay Raghvan has given right explanation

      Delete
  30. find the perpendicular vector to the surface X+Y+Z=5 (Result may be i+j+k=0)

    ReplyDelete
  31. two white balls and 3 black balls in one container and two black ball and 3 white ball are kept in another container...find the probability to get one white ball from the two containers??

    ReplyDelete
    Replies
    1. Anonymous19 June, 2012

      41/70

      Delete
    2. Anonymous20 June, 2012

      I too got 41/70

      Delete
  32. a frame is moving with a velocity x m/s with respect to another inertial frame. the separation between the two frames are given y m...find the time interval between them?

    ReplyDelete
  33. find the correct operator used in quantum mechanics...-ih (del del phy), -ih/sin (theta) (del del phy) etc...

    ReplyDelete
    Replies
    1. -ih/sin(thetha)(del del phy)

      Delete
    2. Anonymous25 June, 2012

      Question was which one of them is hermitian operaor and the answer was -ihcross del operator

      Delete
    3. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : -(ih/2pi)d/d@

      Delete
  34. ans of the question of accuracy and precision will be A: Poor accuracy and high precision and B: poor accuracy and poor precision.

    ReplyDelete
  35. LED with volts 5mV and current 2mp is given. find the no. of photons emitted?

    ReplyDelete
  36. A streamline flow of a liquid is shown with a pipe with both ends with same area but the middle area is made lesser...is pressure will b same throughout the pipe or more in the middle?

    ReplyDelete
    Replies
    1. Pressure is low at middle..

      Delete
    2. Bernouli's theorm

      Delete
    3. Anonymous19 June, 2012

      use the link Click here So answer is pressure is same at A and C

      Delete
  37. Which of these remains invariant under Lorentz transformation?
    Ans. E.B

    Ratio between two moment of inertia
    Ans. 1.032

    SCATTERING CROSS SECTION
    Ans. it is increased by four times

    FOR an analytic function if u= x+(x^2/2) then the value of v is...
    Ans. y+xy

    A man on rotating disc fires a bullet with velocity v horizontally. direction of disc's angular velocity w is upwards. acceleration of the bullet is...
    Ans. 2mwv in the left direction.

    PLEASE COMMENT

    ReplyDelete
    Replies
    1. is it 2mwv to the right

      Delete
    2. Anonymous19 June, 2012

      invariant is |E|^2-|B|^2 ( Ebar.Bbar was not in the options)

      http://en.wikipedia.org/wiki/Classification_of_electromagnetic_fields

      Delete
  38. Anonymous19 June, 2012

    What is the answer to the beaker and iron problem in csir net math ?

    ReplyDelete
  39. What will be the pattern of waves of a simple harmonic oscillator when immersed in water...graphs were given..

    ReplyDelete
    Replies
    1. it is just like damping oscillator. The answer is the spiral towards the origin.

      Delete
    2. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      ABSOLUTELY CORRECT

      Delete
  40. there are two normal mode of vibrations one with frequency w1 and other is 2w1.what is the probability of getting energies less than 4h(cross)w1?

    ReplyDelete
  41. the fundamental lines of two molecules are given..what is the ratio of their moment of inertia?

    ReplyDelete
    Replies
    1. yes thats it!!!! B1/B2=I2/I1

      Delete
  42. Weight of jar A and B is same.
    Because if we suppose both jars were filled upto brim with water then certainly both would have same weight. Now if we put a block of weight w in jar B, ( as the actual question in paper) then the amount of water that will go out of jar B will have same weight as that of block immersed in jar B (Archimedes Principle) , so effectively there is no net change in the weight of jar B. Hence both jar A and B had same weight.

    ReplyDelete
    Replies
    1. but if u place an iron block in one jar and water is upto brim in both case then? as per Archimedes pinciple the loss of weight of the material when immersed in water is equal to the displaced water......

      Delete
    2. Iron block will sink into the water as in that case weight of iron block is more than the weight of maximum water displaced by iron block, hence upward buoyant force could not keep iron block floating and iron block sink down. Then jar B would have been heavy than jar A. However for a floating body (e.g. wood block) ( as the figure was in exam) my above given explanation will work.

      Delete
    3. aman is correct,this problem can be explained using the principle of floatation,That is the weight of the displaced liquid is equal to the total weight of the body/

      Delete
    4. yes,Aman is correct.This can be explained using priciple of floatation which is the weight of the displaced liquid is equal to the total weight of the body.

      Delete
  43. what is the the answer of part c probability problem??? is it N(N+1)/2

    ReplyDelete
    Replies
    1. Anonymous19 June, 2012

      It is N(N-1)/2

      Delete
    2. This comment has been removed by the author.

      Delete
    3. devender is right. total no.=N(N+1)/2.when we take tha average
      it will come (N+1)/2

      Delete
  44. can anyone suggest what is the answer of part c probability question??? is it N(N+1)

    ReplyDelete
    Replies
    1. Anonymous19 June, 2012

      No it is wrong because it is applicable for BEC probability, but it is asked for maxwellian distribution probability.

      Delete
    2. Anonymous23 June, 2012

      how could u say that it was asked for MAXWELL DIST.
      it was clearly mentioned that for bosons find etc etc.
      so ans is n+1

      Delete
  45. Anonymous19 June, 2012

    1)Ratio of inertia for isotope substitution. Answer is 1.08
    2)energy 1eV, and two Temperatuers are given. Then ratio of number of particles proportional to Exp[-30]
    3) BEC condensate. Helium gas 21.7mK

    ReplyDelete
    Replies
    1. Anonymous21 June, 2012

      Ratio of inertia for isotopic substitution is 1.046. It is given in Benwell chapter-microwave spectroscopy.

      Delete
  46. Anonymous19 June, 2012

    Blood Group Answer A & O

    ReplyDelete
    Replies
    1. Anonymous19 June, 2012

      the answer for blood group is A and B

      Delete
    2. Anonymous22 June, 2012

      wrong....it's A & B

      Delete
  47. chemical sciences qs:hw nu- attack at the double bond?

    ReplyDelete
  48. Anonymous19 June, 2012

    chem sc que: for d5 system microscopic states are: (c) 7*6'2

    ReplyDelete
    Replies
    1. who is Anonymous, why he is replying all the questions.. he has been doing this since last three four year....
      do't mislead your junours..

      Delete
  49. Comment all questions completely.. there is a lot of visitor who are not attended the exam make the discussion useful to all ..

    ReplyDelete
    Replies
    1. which one is the best eigen functions for the angular momentas......
      the options are:
      H, Lz,
      H, L2, Lz
      Lx, Ly, Lz
      Lx, Ly

      Delete
    2. The value of magnetic field for a straight wire carrying current I, for a large distanca is varies as

      Delete
    3. If the function as f= 1/(Z-1)(Z-2) then find its laurentz expansion between Z is less than 3/2

      Delete
    4. If Free energy of the system is given then find out the value of system energy
      I have not remember the exact function of free energy value?

      Delete
    5. If the energy of the system is given 14pihcross square/2ml2then find the best combination of the wavefunctions

      Delete
    6. Find the commutation relation of [|r|, |p|]
      1.|r||p|
      2.r^.p^
      3.3
      4.1

      Delete
    7. Best eigen functions of angular momentas are that of L2,LZ and H

      Delete
    8. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : L2 AND LZ

      Delete
    9. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      QUESTION : poission bracket {!r! !p!}

      CORRECT ANSWER : r^ . p^

      Delete
    10. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      QUESTION : Expression for free energy F is given. Calculate the Internal energy

      CORRECT ANSWER : 5/2 NKT

      Delete
    11. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      QUESTION : The magnetic field at a point at adistance R from aconductor carrying current I is
      proportional to

      CORRECT ANSWER : I/R

      Delete
  50. Anonymous20 June, 2012

    answer for double potential well

    ReplyDelete
  51. Anonymous20 June, 2012

    saturated solutin graph

    ReplyDelete
    Replies
    1. Graph was similar to that of charging curve of a capacitor through resistor.

      Delete
    2. This comment has been removed by the author.

      Delete
  52. Anonymous20 June, 2012

    free energy given find internal energy ?is it 3/2kt

    ReplyDelete
  53. 1.if the black body is enclosed in a box of temperature T and then the temp is raised to 2T what is the increase in entropy..a)2times b)4 c)8 d)16

    ReplyDelete
    Replies
    1. The entropy in the case of black body radiation is proportional to T^3 . hence the correct option is 8 times.

      Delete
    2. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : 8 TIMES

      Delete
  54. eigenvalues are 0,0,14

    ReplyDelete
  55. hey what will be this year cut-off for clearing JRF+LS and only LS....please enlighten me

    ReplyDelete
    Replies
    1. Last time it was 35% for LS and 40% for JRF+LS.This time it may go up a bit like 40% for LS and 45% for JRF+LS

      Delete
  56. what is the answer for eigen values of antisymmetric matrix {0 -n2 n3; n2 0 -n1; -n3 n1 0} where n1, n2 & n3 are unit vectors?

    ReplyDelete
  57. Three charges -2Q ,Q ,Q are placed each at the three vertex of an equilateral triangle having side lenght = a .
    Find the dipole moment for this charge configuration independent of the choice of origin.


    A) -2Q*a B) -root3*Q*a C) +root3*Q*a D)0

    Answer is B) -root3*Q*a

    Let us place the origin mid-way between the two positive charges Q such that they lie on the X-axis at equal distance from the origin (a/2)
    So the charge -2Q is at a distance (root3)*a/2 from the origin


    dipole moment p = summation (q * d) = -2Q * (root3)*a/2 + Q*a + Q*(-a) = -root3*Q*a.

    You will get the same answer with any choice of origin you take because when the total charge is zero(monopole moment) then the dipole moment is independent of the origin (Griffith page 151)

    ReplyDelete
  58. atul kumar singh21 June, 2012

    answer for the possible blood group will be A & B.

    ReplyDelete
  59. Hi raj,
    How can u consider, in the dipole moment summation, the 3rd term Q*(-a) it should be Q(+a) i guess. I guess the choise of origin should be considered at the middli of the equilateral triangle. Plz confirm.

    ReplyDelete
  60. what is the vale of poission bracket {|r||p|} is

    ReplyDelete
    Replies
    1. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

      CORRECT ANSWER : r^ . p^

      Delete
  61. Anonymous23 June, 2012

    @Raj nair; just conforming:
    p= -2Q *(root3)*a/2+Q*a/2+Q*(-a/2)=....
    {-------------}this part

    ReplyDelete
  62. how differential scattering cross setion varies when sacttering amplitude doubles in a scatering potential V0

    ReplyDelete
  63. Q: 3-D particle in a box have energy 14∏^2ħ^2/2mL^2 . its wave function
    Ans: (2/L)^3/2 sin(x/L)sin(2x/L)sin(3x/L)

    is it correct

    ReplyDelete
    Replies
    1. no it is not correct........

      Delete
    2. Why is it not correct?

      isnt it like this nx^2 + ny^2 + nz^2 = n^2 we are given n^2 = 14 so (nx,ny,nz) = (1,2,3).

      Delete
    3. Anonymous26 June, 2012

      @ devendra can you explain the reason please?

      Delete
  64. (2/L)^3/2sin(3x/L)sin(5x/L)sin(6x/L)

    ReplyDelete

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