Topic:- DU_J18_PHD_PHY_Topic01
- An infinite long wire carries a time independent current I=1 Ampere. The wire is bent and a semi-circle detour of radius R = 1 cm is made with the centre at the origin. The magnitude of magnetic field at the origin is [Question ID = 19633]
- 25 µ? ? / 4p [Option ID = 48525]
- 2.5 µ? ? [Option ID = 48523]
- 25 µ? ? / p [Option ID = 48524]
- 2.5 µ? ? / 4p [Option ID = 48526]
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- In a rotational structure of electronic bands (the transition between rotational levels of the different electronic levels) having larger rotational constant of the upper electronic level than the lower one, [Question ID = 19617]
- band head appears in R-branch [Option ID = 48460]
- band head appears in P-branch [Option ID = 48459]
- band head appears in Q-branch [Option ID = 48461]
- no band head appears [Option ID = 48462]
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- In a bistable multivibrator, commutating capacitors are used to [Question ID = 19610]
- change the frequency of the output [Option ID = 48433]
- provide a.c. coupling [Option ID = 48432]
- increase the base storage output [Option ID = 48434]
- increase the speed of response [Option ID = 48431]
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- In the Geiger Muller (GM) region, when the applied voltage is increased, which of the following happens: [Question ID = 19623]
- The pulse amplitude increases but the counting rate remains nearly constant. [Option ID = 48483]
- The pulse amplitude remains nearly constant and the counting rate increases. [Option ID = 48484]
- Both the pulse amplitude and the counting rate increases. [Option ID = 48485]
- Both the pulse amplitude and counting rate remain nearly constant. [Option ID = 48486]
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- In the absorption spectra of harmonic vibrating diatomic oscillator, only one spectral line is observed. It is because [Question ID = 19618]
- Separation between any two adjacent E-level is same [Option ID = 48465]
- All other lines are very weak in intensity [Option ID = 48466]
- Only one molecule is present in a particular E-level [Option ID = 48464]
- Only one transition is possible from ground E level to higher E level [Option ID 48463]
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- Magnetic field required to bend a non-relativistic charge particle of energy E in an arc of radius R is [Question ID = 19632]
- inversely proportional to vE and directly proportional to R. [Option ID = 48520]
- directly proportional to E and inversely proportional to R². [Option ID = 48521]
- directly proportional to vE and inversely proportional to R. [Option ID = 48519]
- inversely proportional to vE and directly proportional to R². [Option ID = 48522]
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- The number of ways in which two particles can be distributed in six states, if the particles are indistinguishable and only one particle can occupy any one state, is [Question ID = 19612]
- 31 [Option ID = 48440]
- 36 [Option ID = 48439]
- 21 [Option ID = 48442]
- 25 [Option ID = 48441]
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- Consider a 2-D harmonic oscillator with mass m and frequency w. A perturbation H' = bxy is applied to the system, where x and y are the two spatial coordinates. The first order correction to the ground state energy is [Question ID = 19635]
- 0 [Option ID = 48531]
- bh / 2mw [Option ID = 48534]
- bh / 2mw [Option ID = 48532]
- bh / 2mw [Option ID = 48533]
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- An electron of charge -e is decelerated at a constant rate from an initial velocity vo to rest over a distance d (vo << c). The energy lost to radiation is given by [Question ID = 19630]
- µ? e² vo³ / 6 pcd [Option ID = 48512]
- µ? e² vo³ / 3 pcd [Option ID = 48511]
- Cannot be determined from the information supplied. [Option ID = 48514]
- µ? e² vo³ / 12 pcd [Option ID = 48513]
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- The lattice constant and saturation magnetization of BCC iron at 0 K are 2.87 Å and 1950 kAm?¹, respectively. The net magnetic moment per iron atom in the crystal is [Question ID = 19597]
- 2.30 x 10?²³ A m² [Option ID = 48380]
- 0.67 x 10?²¹ A m² [Option ID = 48382]
- 7.30 x 10?²5 A m² [Option ID = 48379]
- 1.87 x 10?²² A m² [Option ID = 48381]
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- Consider the density matrix of a two level system given by p= |1?1| + |2?2|. Then [Question ID = 19615]
- The expectation value of the operator O2 = |1?2| + |2?1| is h / 2 [Option ID = 48452]
- The expectation value of the operator O1 = |1?1| - |2?2| is h / 2 [Option ID = 48451]
- The system is in a pure state. [Option ID = 48453]
- (O1) = 0, where O1 = |1?1| - |2?2|. [Option ID = 48454]
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- A quantum-mechanical particle of mass m and charge q is subjected to a potential of the form V(x) = ½ mw²x², where w is a constant. An electric field E = E0x is now switched on (E0 being a constant). What is the consequent change, upto second order in E0, in the energy of the second excited state? [Question ID = 19594]
- qE0 / mh? [Option ID = 48368]
- q²E0 ?x²? / (mh?)² [Option ID = 48370]
- q²E0 / 2mw² [Option ID = 48367]
- 2q²E0 / m? [Option ID = 48369]
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- For the infinite square well potential the unperturbed wave functions are ?(x) = v(2/a) sin(np/a x) If the floor of the well is raised by V0, the first order correction to the energy is [Question ID = 19591]
- V0 / 4 [Option ID = 48358]
- V0 / 2 [Option ID = 48356]
- V0 / 3 [Option ID = 48357]
- V0 [Option ID = 48355]
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- Lead (Pb) starts superconducting at 7.19 K when the applied magnetic field is zero. When a magnetic field of 0.074 Tesla is applied at 2 K, superconductivity disappears. The critical magnetic field for Lead (Pb) is [Question ID = 19599]
- 0.04 T [Option ID = 48388]
- 0.08 T [Option ID = 48390]
- 0.034 T [Option ID = 48387]
- 0.068 T [Option ID = 48389]
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- If A and B are two linear operators, then the commutator bracket [A, B?¹] is equal to [Question ID = 19586]
- A?¹[A, B] B?¹ [Option ID = 48335]
- -A?¹[A, B] A?¹ [Option ID = 48336]
- B?¹[A, B] A?¹ [Option ID = 48337]
- -B?¹[A, B] B?¹ [Option ID = 48338]
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- For a simple harmonic oscillator of mass m and angular frequency w, let |n? represent the n-th energy eigenstate so that H |n? = h? (n + ½) |n?. The physical state at time t = 0 is represented by |?(0)? = |2? - |3? - |1?. If one makes a measurement of the energy of the system at any subsequent time t, the probability of finding the energy to be 3h?/2: [Question ID = 19589]
- depends on time t. [Option ID = 48350]
- is ½ [Option ID = 48348]
- is 1/6. [Option ID = 48349]
- is 0. [Option ID = 48347]
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- For temperatures 10 K and 20 K, a superconductor has the critical magnetic field as 0.15 Tesla and 0.60 Tesla, respectively. The transition temperature for this superconductor in Kelvin is [Question ID = 19596]
- 23.3 [Option ID = 48378]
- 15.0 [Option ID = 48376]
- 22.4 [Option ID = 48377]
- 4.2 [Option ID = 48375]
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- A theory has equally spaced nondegenerate energy levels starting from Emin = E0 all the way upto E8. The system of many such particles is at equilibrium at a temperature T. If the average energy-squared of the particles is given by ?E²? = 5E0², What is T? [Question ID = 19614]
- T = E0/2k? [Option ID = 48449]
- T = 2E0/k? [Option ID = 48448]
- T = 3E0/2k? [Option ID = 48450]
- T = E0/k? [Option ID = 48447]
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- The Hamiltonian for a spin ½ particle of mass m in an external field is given by H = p²/2m + g(t)s.p where g(t) is a time-dependent coupling constant and s are the Pauli matrices. Which of the following statements is true? [Question ID = 19590]
- The energy and all the components of the spin angular momentum of the particle are conserved. [Option ID = 48351]
- The linear momentum and all the components of the spin angular momentum of the particle are conserved. [Option ID = 48354]
- The linear momentum and the magnitude of the spin angular momentum of the particle are conserved.
- The linear momentum and the energy of the particle are conserved. [Option ID = 48352]
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- A solid contains N spin-half magnetic atoms. At sufficiently high temperatures, the atoms are randomly oriented, while at sufficiently low temperatures, they are perfectly aligned. The heat capacity is given by C(T) = C0(e^(T0/T) - 1)?¹, T0 = T = 3T0, 0, Otherwise where C0 and T0 are constants. Determine the maximum value of C0. [Question ID = 19613]
- NkB ln2 / (2-ln3) [Option ID = 48445]
- NkB ln2 / 2 [Option ID = 48443]
- 2NkB ln2 / (2+ln3) [Option ID = 48446]
- NkB ln2 / ln3 [Option ID = 48444]
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- Green's function corresponding to the Laplacian operator ?² is G(r, r') = 1 / (4p|r - r'|) The value of f(0) corresponding to the solution of the inhomogeneous differential equation ?²f = A exp(-ßr) / r (where A and ß are positive numbers) is equal to, [Question ID = 19625]
- 0 [Option ID = 48491]
- A / 4pß [Option ID = 48494]
- A / ß [Option ID = 48492]
- A / pß [Option ID = 48493]
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- A star is pulsating isotropically. Its gravitational force on any body, at distances much larger than its own mean radius, is given by F(r) = (k/r) + (a/r²) r^ where k and a are positive constants. Which of the following is true about the motion of the body? [Question ID = 19604]
- Any bounded motion is described by a precessing ellipse. [Option ID = 48407]
- No bounded motion exists at all. [Option ID = 48410]
- Any bounded motion is described by a pulsating ellipse. [Option ID = 48408]
- Any bounded motion is still in an elliptical path, but the parameters of the ellipse are shifted from those in the Newtonian case. [Option ID = 48409]
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- The Hamiltonian for a particle in one dimension is given by H(x, p) = p²/2m + ?px + ½?²x² where m, ? are constants. The corresponding Lagrangian is [Question ID = 19603]
- L = ½m(?)² - ?m?x - ½?²x² [Option ID = 48405]
- L = ½m(? - ?x)² - ?m?x - ½?²x² [Option ID = 48406]
- L = ½m(? - ?x)² - ½?²x² [Option ID = 48404]
- L = ½m(?)² - ½?²x² [Option ID = 48403]
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- Consider the 2p -periodic function f(x) defined as f(x) = x(p - x), x ? [0,p] x(x - p), x ? [p,0] Which of the following is true? [Question ID = 19627]
- f(x) = - S(k=0 to 8) 4p / (2k+1)³ sin[(2k+1)x] [Option ID = 48502]
- f(x) = S(k=0 to 8) 8 / pk sin(kx) [Option ID = 48500]
- f(x) = S(k=0 to 8) 4 / pk² sin(kx) + cos(kx) [Option ID = 48499]
- f(x) = S(k=0 to 8) 4p / (2k+1)8 sin[(2k+1)x] [Option ID = 48501]
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- In 3-dimensional space, a particle of mass m moves in a potential A cos²ßr where r is the distance of the particle from the origin, A and ß are real constants. Which of the following statements are correct? [Question ID = 19600]
- The motion is periodic in r with an oscillation distance p/ß. [Option ID = 48394]
- The motion is periodic in r with an oscillation distance 2p/ß. [Option ID = 48392]
- The trajectory of the particle is always confined to some plane passing through the origin. [Option ID = 48391]
- The radial momentum p? is conserved because of the periodic nature of the potential. [Option ID = 48393]
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- The ?°Sr ? ?°Y ? ?°Zr chain decays with a half-life of 28 years and 64 hours, respectively. If 1g of pure ?°Sr is allowed to decay, then the ratio (Nsr/Ny) after 1 hour is [Question ID = 19621]
- 3.56 × 104 [Option ID = 48477]
- 3.56 × 105 [Option ID = 48475]
- 4.56 × 104 [Option ID = 48478]
- 4.56 × 105 [Option ID = 48476]
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- For the electronic configuration 2p3d, the complete spectroscopic terms in Russel-Saunders coupling scheme are [Question ID = 19587]
- ¹P, ¹D, ¹F, ¹G, ¹H, ³P, ³D, ³F, ³G, ³H [Option ID = 48339]
- ²P, ²D, ²F, 4P, 4D, 4F [Option ID = 48342]
- ²S, ²P, ²D, ²F, 4S, 4P, 4D, 4F [Option ID = 48340]
- ¹P, ¹D, ¹F, ³P, ³D, ³F [Option ID = 48341]
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- The Hamiltonian of a two-level system is given by H = ½h?sz. At time t = 0 the system is in the eigenstate of sz having the largest eigenvalue. The expectation values ?sx?(t), ?sy?(t) and ?sz?(t) (where s? are Pauli matrices) are respectively [Question ID = 19592]
- sin(?t/2), 0, and cos(?t/2) [Option ID = 48361]
- cos(?t/2), sin(?t/2) and 0 [Option ID = 48359]
- 0, cos(?t/2) and sin(?t/2) [Option ID = 48360]
- cos(?t/2), 0, and sin(?t/2) [Option ID = 48362]
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- The Lagrangian for a system is given by L = q1q2 - ?²q1q2 where ? is a constant and q? = d/dt q?. L is invariant under the following transformations q1 ? e^(a)q1 and q2 ? e^(a)q2, a is a constant. The conserved quantity corresponding to this symmetry transformation is [Question ID = 19601]
- q1q1 + q2q2 [Option ID = 48398]
- q1q2 - q2q1 [Option ID = 48395]
- q1q2 + q2q1 [Option ID = 48396]
- q1q1 - q2q2 [Option ID = 48397]
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- An integral is defined to be, I = ?(0 to 8) sinx / x dx. Then I is equal to: [Question ID = 19628]
- p / cosv2 [Option ID = 48506]
- p / 2 [Option ID = 48503]
- 2 / p cosv2 [Option ID = 48505]
- p / cosv2 [Option ID = 48504]
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- In the given astable multivibrator, the frequency of the square wave generated is [Question ID = 19607]
- 32.4 kHz [Option ID = 48421]
- 3.5 kHz [Option ID = 48419]
- 324 Hz [Option ID = 48422]
- 3.5 Hz [Option ID = 48420]
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- A point mass m is attached, through a massless incompressible rod of length l, to a fixed point. The mass is allowed to have any motion consistent with the above. If ? be the instantaneous angle of the rod with the vertical, which of the following is necessarily true? (Here ? = 0 is an arbitrary constant) [Question ID = 19605]
- ?¨ + ?/l sin? = 0 [Option ID = 48412]
- ?¨ + (? sin?) / (ml²) + (g/l) sin? = 0 [Option ID = 48413]
- ?¨ + (g/l) sin? = 0 [Option ID = 48411]
- ?¨ + (?cos?) / (ml²) + (g/l) sin? = 0 [Option ID = 48414]
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- Neutrons are captured by ¹°B to form ¹¹B, which breaks into an alpha particles and the 7Li nucleus. Then, the kinetic energy of the 7Li and the Q value of the reaction are (Given M(¹°B) = 10.01611 amu; M(n) = 1.008987 amu; M(7Li) = 7.01822 amu; M(4He)= 4.003879 amu) [Question ID = 19620]
- 1.01 MeV and 2.59 MeV [Option ID = 48473]
- 1.78 MeV and 2.79 MeV [Option ID = 48472]
- 1.01 MeV and 2.79 MeV [Option ID = 48471]
- 1.78 MeV and 2.59 MeV [Option ID = 48474]
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- An ultrafast laser produces a sequence of pulses with a repetition time of T. The pulse is a wavepacket of energy E and a central wavelength of ?. The laser beam hits a mirror at an angle ? to the normal and is reflected. The average force on the mirror is [Question ID = 19629]
- None of these [Option ID = 48510]
- 2 E cos ? / cT [Option ID = 48509]
- E cos ? / cT [Option ID = 48507]
- E cos 2? / cT [Option ID = 48508]
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- The canonical partition function for a system of N non interacting particles is given by (akT)³?, where a and k are constants. The internal energy of the system is (large N) [Question ID = 19616]
- 3NkT [Option ID = 48457]
- NkT / 2 [Option ID = 48455]
- 2NkT [Option ID = 48456]
- 6NkT [Option ID = 48458]
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- The acceleration of the system given in the figure, where k is the spring constant and x is the displacement relative to the relaxed length of the spring, is [Question ID = 19626]
- (-kx + m1g) / (m1 + m2) [Option ID = 48497]
- (kx - m2g) / (m1 + m2) [Option ID = 48496]
- (-kx + m2g) / (m1 + m2) [Option ID = 48495]
- (kx - m1g) / (m1 + m2) [Option ID = 48498]
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- A system, in three dimensions, is described by the Lagrangian L = ½m(?² + ?² + z²) + ? sin(t) - ½k(x² + y²) + x cos(t) where k is constant. Of energy (E), linear momentum (p) and angular momentum (J), which are conserved? [Question ID = 19602]
- p2 alone [Option ID = 48399]
- E, p, and J. alone. [Option ID = 48402]
- E, p, J [Option ID = 48401]
- p alone [Option ID = 48400]
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- For a simple harmonic oscillator of mass m and angular frequency w, if |n? represents the n-th energy eigenstate, then the expectation value ?n|p²|n? is equal to: [Question ID = 19588]
- mhnw [Option ID = 48345]
- mhw (n + ½) [Option ID = 48343]
- mhw (2n + 1) [Option ID = 483
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