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

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1. Anonymous17 June, 2012

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

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

2. Anonymous19 June, 2012

it should be A or B. NOT O

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.

4. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

CORRECT ANSWER : A , B BLOOD GROUPS

2. Anonymous17 June, 2012

d' < 2d

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

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

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.

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

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, ?

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

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.

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

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

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

4. Anonymous18 June, 2012

weight is same
slope 1<m<root3

paper was very very tough

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

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

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

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

4. @Rani George : Q) Find the allowed multipole transitions between the states (5/2)^- and (1/2)^-
were the raised to minus sign indicates an odd parity for booth the states.
A) E2 M2 B) E2 M3 C)E3 M2 D) E3 M3

Ans) Multipole transition are given by E(l) and M(l) were l is the angular momentum difference between initial and final state.So l = 2 or 3.
If there is no change in parity we have only even electric and odd magnetic.
In our case there is no change in parity so E2 and M3 is the answer.

Also option A) and D) are never possible in any case becoz if electric is even then magnetic has to be odd and vice-verse.

6. Anonymous18 June, 2012

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

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

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.

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

3. it is also correct,

4. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

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

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

The rate of photosynthesis increases as the humidity increases.

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

2. Anonymous19 June, 2012

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

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

4. Anonymous19 June, 2012

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

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

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.

9. Anonymous18 June, 2012

What about the velocity time graph

1. Anonymous18 June, 2012

straight line

2. Anonymous18 June, 2012

option a

3. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

CORRECT ANSWER : straight line graph

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

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

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?

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

11. opamp ans -1
digital electronics ans 111

12. no of suares is 15

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.

2. Anonymous21 June, 2012

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

3. Anonymous25 June, 2012

Yes 17 are there

4. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

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

13. Anonymous18 June, 2012

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

1. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

above mentioned matches are absolutely correct

14. How many square was there?

1. total no. of square is 17

2. Anonymous19 June, 2012

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

15. [ X2,P2] = ?

Ans: 2ih[px+xp]

1. Anonymous18 June, 2012

it should be 2ihxp

2. This comment has been removed by the author.

3. Anonymous18 June, 2012

@MUTHU is correct

4. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

16. Anonymous18 June, 2012

output of digital circuit (1,1)

1. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

CORRECT

17. Anonymous18 June, 2012

weight is equal of both jar A and B

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.

1. ravi kumar g raj nair absolutely right

2. Anonymous23 June, 2012

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

3. Anonymous24 June, 2012

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

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)

20. Anonymous18 June, 2012

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

1. Anonymous20 June, 2012

wrong. ryt ans is 0,0,0

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

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

21. Anonymous18 June, 2012

0, -i, i correct

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

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.

2. Anonymous18 June, 2012

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

3. Anonymous20 June, 2012

pressure balance is the right answer..

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

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

2. ratio of daughter parent nuclei after 2 half lifes

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

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

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...

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?

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

8. Anonymous20 June, 2012

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 )

1. yes option D

2. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

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

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?

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

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

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

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

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

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

1. N+1 ways.

2. Anonymous20 June, 2012

is it sure

3. 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??!

4. Anonymous22 June, 2012

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

5. @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..........."

6. This comment has been removed by the author.

7. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

@Vijay Raghvan has given right explanation

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

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??

1. Anonymous19 June, 2012

41/70

2. Anonymous20 June, 2012

I too got 41/70

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?

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

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

2. Anonymous25 June, 2012

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

3. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

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

1. yes you are correct

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

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?

1. Pressure is low at middle..

2. Bernouli's theorm

3. Anonymous19 June, 2012

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.

1. is it 2mwv to the right

2. ratio 1.048

38. Anonymous19 June, 2012

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

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

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

2. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

ABSOLUTELY CORRECT

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?

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

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

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.

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......

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.

3. the ans is Vpg-w

4. 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/

5. 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.

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

1. No it is N+1/2

2. Anonymous19 June, 2012

It is N(N-1)/2

3. This comment has been removed by the author.

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

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

1. Anonymous19 June, 2012

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

2. it will be N+1

3. it will be n+1

4. 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

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

1. Anonymous21 June, 2012

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

46. Anonymous19 June, 2012

Blood Group Answer A & O

1. Anonymous19 June, 2012

the answer for blood group is A and B

2. Anonymous22 June, 2012

wrong....it's A & B

3. Anonymous26 June, 2012

Its A and B.

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

48. Anonymous19 June, 2012

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

1. who is Anonymous, why he is replying all the questions.. he has been doing this since last three four year....

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

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

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

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

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?

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

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

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

8. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

CORRECT ANSWER : L2 AND LZ

9. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

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

CORRECT ANSWER : r^ . p^

10. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

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

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

50. Anonymous20 June, 2012

51. Anonymous20 June, 2012

saturated solutin graph

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

52. Anonymous20 June, 2012

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

1. internal energy is 5/2kt

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

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

2. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

54. eigenvalues are 0,0,14

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

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

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?

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

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)

58. atul kumar singh21 June, 2012

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

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.

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

1. DEPTT OF PHYSICS, JAMMU UNIVERSITY26 June, 2012

CORRECT ANSWER : r^ . p^

61. Anonymous23 June, 2012

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

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

63. LED - no: of photons

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

is it correct

1. no it is not correct........

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).

3. Anonymous26 June, 2012

@ devendra can you explain the reason please?

4. Yes Right answer. n^2 = nx^2 +ny^2 + nz^2 = 1^2 + 2^2 + 3^2 = 1 + 4 + 9 = 14.
So the above Shhna mentioned wave funciton is right answer.

65. (2/L)^3/2sin(3x/L)sin(5x/L)sin(6x/L)