Instructions

For the following questions answer them individually

Question 51

A student performed the experiment of determination of focal length of a concave mirror by u-v method using an optical bench of length 1.5 meter. The focal length of the mirror used is 24 cm. The maximum error in the location of the image can be 0.2 cm. The 5 sets of (u, v) values recorded by the student (in cm) are : (42, 56), (48, 48), (60, 40), (66, 33), (78, 39). The data set(s) that cannot come from experiment and is(are) incorrectly recorded, is (are)

Question 52

$$C_v$$ and $$C_p$$ denote the molar specific heat capacities of a gas at constant volume and constant pressure, respectively. Then

Instructions

Scientists are working hard to develop nuclear fusion reactor. Nuclei of heavy hydrogen, $$_{1}^{2}H$$, known as deuteron and denoted by D, can be thought of as a candidate for fusion reactor. The D-D reaction is $$_{1}^{2}H + _{1}^{2}H \rightarrow _{2}^{3}He + n +$$ energy. In the core of fusion reactor, a gas of heavy hydrogen is fully ionized into deuteron nuclei and electrons. This collection of $$_{1}^{2}H$$ nuclei and electrons is known as plasma. The nuclei move randomly in the reactor core and occasionally come close enough for nuclear fusion to take place. Usually, the temperatures in the reactor core are too high and no material wall can be used to confine the plasma. Special techniques are used which confine the plasma for a time $$t_0$$ before the particles fly away from the core. If n is the density (number/volume) of deuterons, the product nt0 is called Lawson number. In one of the criteria, a reactor is termed successful if Lawson number is greater than $$5 \times 10^{14}$$ s/cm$$^3$$.

It may be helpful to use the following. Boltzmann constant $$k = 8.6 \times 10^{-5}$$eV/K; $$\frac{e^2}{4 \pi \varepsilon_0} = 1.44 \times 10^{-9}$$ eVm.

Question 54

Assume that two deuteron nuclei in the core of fusion reactor at temperature T are moving towards each other, each with kinetic energy 1.5 kT, when the separation between them is large enough to neglect Coulomb potential energy. Also neglect any interaction from other particles in the core. The minimum temperature T required for them to reach a separation of $$4 \times 10^{-15}$$ m is in the range-

Question 55

Results of calculations for four different designs of a fusion reactor using D-D reaction are given below. Which of these is most promising based on Lawson criterion ?

Instructions

When a particle is restricted to move along x-axis between x = 0 and x = a, where a is of nanometer dimension, its energy can take only certain specific values. The allowed energies of the particle moving in such a restricted region, correspond to the formation of standing waves with nodes at its ends x = 0 and x = a. The wavelength of this standing wave is related to the linear momentum p of the particle according to the de Broglie relation. The energy of the particle of mass m is related to its linear momentum as $$E = \frac{p^2}{2m}$$. Thus, the energy of the particle can be denoted by a quantum number 'n' taking values 1, 2, 3, . . . . . (n = 1, called the ground state) corresponding to the number of loops in the standing wave.

Use the model described above to answer the following three questions for a particle moving in the line x = 0 to

$$x = a$$. Take $$h = 6.6 \times 10^{-34}$$J-s and $$e = 1.6 \times 10^{-19}$$ C.

Question 57

If the mass of the particle is $$m = 1.0 \times 10^{-30}$$ kg and a = 6.6 nm, the energy of the particle in its ground state is closest to -

Instructions

This section contains 2 questions. Each question contains statements given in two columns, which have to be matched. The statements in Column I are labelled A, B, C and D, while the statements in Column II are labelled p, q, r, s and t. Any given statement in Column I can have correct matching with ONE OR MORE statement(s) in Column II. The appropriate bubbles corresponding to the answers to these questions have to be darkened as illustrated in the following example.

If the correct matches are A - p, s and t; B - q and r; C - p and q; and D - s and t; then the correct darkening of bubbles will look like the following.

Question 59

Six point charges, each of the same magnitude q, are arranged in different manners as shown in Column II. In each case, a point M and a line PQ passing through M are shown. Let E be the electric field and V be the electric potential at M (potential at infinity is zero) due to the given charge distribution when it is at rest. Now, the whole system is set into rotation with a constant angular velocity about the line PQ. Let B be the magnetic field at M and $$\mu$$ be the magnetic moment of the system in this condition. Assume each rotating charge to be equivalent to a steady current.

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Question 60

Column II shows five systems in which two object are labelled as X and Y. Also in each case a point P is shown. Column I gives some statements about X and/or Y. Match these statements to the appropriate system(s) from Column II.

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