JEE Main 2020 Question Paper (08-Jan-2020) (Shift 1)

Question 1

The critical angle of a medium for a specific wavelength, if the medium has relative permittivity $3$ and relative permeability $\frac{4}{3}$ for this wavelength, will be:

Accepted Answer

$30^{\circ}$

Answer

$15^{\circ}$

Answer

$45^{\mathrm{o}}$

Answer

$60^{\circ}$

Question 2

Effective capacitance of parallel combination of two capacitors $ C_{1} $ and $ C_{2} $ is $ 10\,\mu\mathrm{F} $. When these capacitors are individually connected to a voltage source of $ 1\,\mathrm{V} $, the energy stored in the capacitor $ C_{2} $ is 4 times that of $ C_{1} $. If these capacitors are connected in series, their effective capacitance will be:

Accepted Answer

$1.6\,\mu\mathrm{F}$

Answer

$4.2\,\mathrm{\mu F}$

Answer

$3.2\,\mathrm{\mu F}$

Answer

$8.4\,\mu\mathrm{F}$

Question 3

The coordinates of the centre of mass of a uniform flag-shaped lamina (thin flat plate) of mass $4 \mathrm{kg}$ (The coordinates of the same are shown in the figure) are:

Accepted Answer

$\left(0.75\ \mathrm{m},\ 1.75\ \mathrm{m}\right)$

Answer

$\left(1.25\ \mathrm{m},\ 1.50\ \mathrm{m}\right)$

Answer

$\left(0.75\ \mathrm{m},\ 0.75\ \mathrm{m}\right)$

Answer

$\left(1\ \mathrm{m},\ 1.75\ \mathrm{m}\right)$

Question 4

A particle of mass $m$ is fixed to one end of a light spring having force constant $k$ and unstretched length $l$. The other end is fixed. The system is given an angular speed $\omega$ about the fixed end of the spring such that it rotates in a circle in gravity-free space. Then the stretch in the spring is:

Accepted Answer

$\frac{ml{\omega }^{2}}{k - m{\omega }^{2}}$

Answer

$\frac{m l \omega^{2}}{k - \omega m}$

Answer

$\frac{ml \omega^{2}}{k + m \omega^{2}}$

Answer

$ \frac{m l \omega^{2}}{k + m \omega} $

Question 5

A thermodynamic cycle $xyzx$ is shown on a $V$ - $T$ diagram. The $P$ - $V$ diagram that best describes this cycle is: (Diagrams are schematic and not to scale)

Accepted Answer

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Answer

Answer

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