JEE Advance - Physics (2015 - Paper 2 Offline)

1
Consider a uniform spherical charge distribution of radius $${R_1}$$ centred at the origin $$O.$$ In this distribution, a spherical cavity of radius $${R_2},$$ centred at $$P$$ with distance $$OP=a$$ $$ = {R_1} - {R_2}$$ (see figure) is made. If the electric field inside the cavity at position $$\overrightarrow r $$ is $$\overrightarrow E \overrightarrow {\left( r \right)} ,$$ then the correct statement(s) is (are)

답변
(D)
$$\overrightarrow E $$ is uniform and both its magnitude and direction depend on $$\overrightarrow a $$
2
A spherical body of radius R consists of a fluid of constant density and is in equilibrium under its own gravity. If P(r) is the pressure at r (r < R), then the correct option(s) is(are)
답변
B
C
3
The densities of two solid spheres A and B of the same radii R vary with radial distance r as $${\rho _A}(r) = k\left( {{r \over R}} \right)$$ and $${\rho _B}(r) = k{\left( {{r \over R}} \right)^5}$$, , respectively, where k is a constant. The moments of inertia of the individual spheres about axes passing through their centres are $${I_A}$$ and $${I_B}$$, respectively. If, $${{{I_B}} \over {{I_A}}} = {n \over {10}}$$, the value of n is
답변
6
4
The energy of a system as a function of time t is given as E(t) = $${A^2}\exp \left( { - \alpha t} \right)$$, where $$\alpha = 0.2\,{s^{ - 1}}$$. The measurement of A has an error of 1.25 %. If the error in the measurement of time is 1.50 %, the percentage error in the value of E(t) at t = 5 s is
답변
4
5
In terms of potential difference V, electric current I, permittivity $${\varepsilon _0}$$, permeability $${\mu _0}$$ and speed of light c, the dimensionally correct equation(s) is(are) :
답변
A
C
6
Four harmonic waves of equal frequencies and equal intensities I₀ have phase angles 0, $${\pi \over 3},{{2\pi } \over 3}$$ and $$\pi$$. When they are superposed, the intensity of the resulting wave is nI₀. The value of n is
답변
3
7
For a radioactive material, its activity A and rate of change of its activity R are defined as $$A = - {{dN} \over {dt}}$$ and $$R = - {{dA} \over {dt}}$$, where N(t) is the number of nuclei at time t. Two radioactive source P(mean life $$\tau $$) and Q (mean life 2$$\tau $$) have the same activity at t = 0. Their rate of change of activities at t = 2$$\tau $$ are R_P and R_Q, respectively. If $${{{R_P}} \over {{R_Q}}} = {n \over e}$$, then the value of n is
답변
2
8
A monochromatic beam of light is incident at 60$$^\circ$$ on one face of an equilateral prism of refractive index n and emerges from the opposite face making an angle $$\theta$$(n) with the normal (see figure). For n = $$\sqrt 3 $$ the value of $$\theta$$ is 60$$^\circ$$ and $${{d\theta } \over {dn}} = m$$. The value of m is

답변
2
9
In the following circuit, the current through the resistor R(=2$$\Omega$$) is I amperes. The value of I is :

답변
1
10
An electron in an excited state of Li²⁺ ion has angular momentum $${{3h} \over {2\pi }}$$. The de Broglie wavelength of the electron in this state is p$$\pi$$a₀ (where a₀ is the Bohr radius). The value of p is
답변
2
11
A large spherical mass M is fixed at one position and two identical masses m are kept on a line passing through the centre of M (see figure). The point masses are connected by a rigid massless rod of length l and this assembly is free to move along the line connecting them.

All three masses interact only through their mutual gravitational interaction. When the point mass nearer to M is at a distance r = 3l from M the tension in the rod is zero for m = $$k\left( {{M \over {288}}} \right)$$. The value of k is
답변
7
12
In plotting stress versus strain curves for two materials P and Q, a student by mistake puts strain on the y-axis and stress on the x-axis as shown in the figure. Then, the correct statements is/are

답변
A
B
13
A parallel plate capacitor having plates of area S and plate separation d, has capacitance C₁ in air. When two dielectrics of different relative permittivities ($$\varepsilon $$₁ = 2 and $$\varepsilon $$₂ = 4) are introduced between the two plates as shown in the figure, the capacitance becomes C₂. The ratio $${{{C_2}} \over {{C_1}}}$$ is

답변
(D)
$${7 \over 3}$$
14
An ideal monoatomic gas is confined in a horizontal cylinder by a spring loaded piston (as shown in the figure). Initially the gas is at temperature T₁, pressure P₁ and volume V₁ and the spring is in its relaxed state. The gas is then heated very slowly to temperature T₂, pressure P₂ and volume V₂. During this process the piston moves out by a distance x.

Ignoring the friction between the piston and the cylinder, the correct statements is/are

답변
B
C
A
15
A fission reaction is given by $$_{92}^{236}U \to _{54}^{140}Xe + _{38}^{94}Sr + x + y$$, where x and y are two particles. Considering $$_{92}^{236}U$$ to be at rest, the kinetic energies of the products are denoted by $${K_{Xe}},{K_{Sr}},{K_x}(2MeV)$$ $$ \text { and } \mathrm{K}_{\mathrm{y}}(2 \mathrm{MeV}) $$, respectively. Let the binding energies per nucleon of $$_{92}^{236}U$$, $$_{54}^{140}Xe$$ and $$_{38}^{94}Sr$$ be 7.5 MeV, 8.5 MeV and 8.5 MeV, respectively. Considering different conservation laws, the correct options is/are
답변
(A)
x = n, y = n, K_sr = 129 MeV, K_Xe = 86 MeV
16
Two spheres P and Q for equal radii have densities $$\rho$$₁ and $$\rho$$₂, respectively. The spheres are connected by a massless string and placed in liquids L₁ and L₂ of densities $$\sigma$$₁ and $$\sigma$$₂ and viscosities $${\eta _1}$$ and $${\eta _2}$$, respectively. They float in equilibrium with the sphere P in L₁ and sphere Q in L₂ and the string being taut (see figure) If sphere P along in L₂ has terminal velocity v_P and Q alone in L₁ ha terminal velocity v_Q, then

답변
A
D
17
For two structures namely S₁ with n₁ = $${{\sqrt {45} } \over 4}$$ and n₂ = $${3 \over 2}$$, and S₂ with n₁ = $${8 \over 5}$$ and n₂ = $${7 \over 5}$$ and taking the refractive index of water to be $${4 \over 3}$$ and that to air to be 1, the correct options is/are :
답변
A
C
18
If two structures of same cross-sectional area, but different numeral apertures NA₁ and NA₂ (NA₂ < NA₁) are joined longitudinally, the numerical aperture of the combined structure is
답변
(D)
$$N{A_2}$$
19
Consider two different metallic strips (1 and 2) of the same material. Their lengths are the same, widths are w₁ and w₂ and thickness are d₁ and d₂, respectively. Two points K and M are symmetrically located on the opposite faces parallel to the x-y plane (see figure). V₁ and V₂ are the potential differences between K and M in strips 1 and 2, respectively. Then, for a given current I flowing through them in a given magnetic field strength B, the correct statements is/are
답변
A
D
20
Consider two different metallic strips (1 and 2) of same dimensions (length l, width w and thickness d) with carrier densities n₁ and n₂, respectively. Strip 1 is placed in magnetic field B₁ and strip 2 is placed in magnetic field B₂, both along positive y-directions. Then V₁ and V₂ are the potential differences developed between K and M in strips 1 and 2, respectively. Assuming that the current I is the same for both the strips, the correct options is/are :
답변
A
C