JEE Main 2017 Question Paper (09-Apr-2017)

Question 1

The electric field component of a monochromatic radiation is given by $ \overrightarrow{E} = 2 E_0 \cos(kz) \cos(\omega t) \, \widehat{\imath}. $ Its magnetic field $\overrightarrow{B}$ is then given by:

Accepted Answer

$ \frac{2E_{0}}{c} \sin kz \sin \omega t \quad \widehat{\mathbf{j}} $

Answer

$ \frac{2E_0}{c} \cos kz \cos \omega t \quad \widehat{\mathbf{j}} $

Answer

$ \frac{2E_0}{c} \sin kz \cos \omega t \quad \widehat{\mathbf{j}} $

Answer

$ \frac{-2E_{0}}{c} \sin kz \sin \omega t \quad \widehat{j} $

Question 2

$N$ moles of diatomic gas in a cylinder is at a temperature $T$. Heat is supplied to the cylinder such that the temperature remains constant but $n$ moles of the diatomic gas get converted into monoatomic gas. The change in the total kinetic energy of the gas is

Accepted Answer

$\frac{1}{2} nRT$

Answer

$0$

Answer

$ \frac{5}{2} nRT $

Answer

$\frac{3}{2} nRT$

Question 3

A circular hole of radius $ \frac{R}{4} $ is made in a thin uniform disc having mass and radius $ R $, as shown in the figure. The moment of inertia of the remaining portion of the disc about an axis passing through the point $ O $ and perpendicular to the plane of the disc is-

Accepted Answer

$\frac{237M R^{2}}{512}$

Answer

$\frac{219M R^{2}}{256}$

Answer

$\frac{197M R^{2}}{256}$

Answer

$\frac{19 M R^{2}}{512}$

Question 4

A block of mass $0.1 \mathrm{kg}$ is connected to an elastic spring of spring constant $640 \mathrm{N} \mathrm{m}^{-1}$ and oscillates in a damping medium of damping constant $10^{-2} \mathrm{kg} \mathrm{s}^{-1}$. The system dissipates its energy gradually. The time taken for its mechanical energy of vibration to drop to half of its initial value is closest to-

Accepted Answer

$7 \mathrm{s}$

Answer

$2 \mathrm{s}$

Answer

$5 \mathrm{s}$

Answer

$3 \mathrm{s}$

Question 5

A steel rail of length $5 \mathrm{m}$ and area of cross section $40 \mathrm{cm}^2$ is prevented from expanding along its length while the temperature rises by $10^\circ \mathrm{C}$. If the coefficient of linear expansion and Young's modulus of steel are $1.2 	imes 10^{-5}  \mathrm{K}^{-1}$ and $2 	imes 10^{11} \mathrm{N} \, \mathrm{m}^{-2}$ respectively, the force developed in the rail is approximately:

Accepted Answer

$1 	imes 10^{5} \mathrm{N}$

Answer

$2 	imes 10^{7} \mathrm{N}$

Answer

$2 	imes 10^{9} \mathrm{N}$

Answer

$3 	imes 10^{-5} \mathrm{N}$