Recent questions in JEEMAIN and NEET

A granite rod of 60 cm length is clamped at its middle point and is set into longitudinal vibrations. The density of granite is $2.7 \times 10^3 kg/m^3$ and its Young's modulus is $9.27 \times 10^{10}$ Pa. What will be the fundamental frequency of the longitudinal vibrations?

asked Dec 11, 2018 by pady_1

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A telephonic communication service is working at carrier frequency of 10 GHz. Only 10% of it is utilized for transmission. How many telephonic channels can be transmitted simultaneously if each channel requires a bandwidth of 5 kHz?

asked Dec 11, 2018 by pady_1

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For an RLC circuit driven with voltage of amplitude $v_m$ and frequency $\omega_o = \frac{1}{\sqrt{LC}}$ the current exhibits resonance. The quality factor, Q is given by :

asked Dec 11, 2018 by pady_1

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A parallel plate capacitor of capacitance $90\; pF$ is connected to a battery of emf $20V$ . If a dielectric material of dielectric constant $K = \frac{5}{3}$ is inserted between the plates, the magnitude of the induced charge will be :

asked Dec 11, 2018 by pady_1

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An electron, a proton and an alpha particle having the same kinetic energy are moving in circular orbits of radii $r_e, r_p, r_{\alpha}$ respectively in unifrom magnetic field B. The relation between $r_e, \; r_p, \; r_\alpha$ is :

asked Dec 11, 2018 by pady_1

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The reading of the ammeter for a silicon diode in the given circuit is :

asked Dec 11, 2018 by pady_1

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An electron from various excited states of hydrogen atom emit radiation of come to the ground state. Let $\lambda_n\; \lambda_g$ be the de Broglie wavelength of the electron in the $n^{th}$ state and the ground state respectively. Let $\bigwedge_{n}$ be the wavelength of the emitted photon in transition from the $n^{th}$ state to the ground state. For large $n$ (A, B are constants)

asked Dec 11, 2018 by pady_1

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Unpolarized light of intensity I passes through an ideal polarized A. Another identical polarizer B is placed behind A. The intensity of light beyond B is found to be $\frac{I}{2}$ . Now another identical polarizer C is placed between A and B. The intersity beyond B is now found to be $\frac{I}{8}$ . The angle between polarizer A and C is :

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If the series limit frequency of the Lyman series is $v_{_L}$ , then the series limit frequency of the Pfund series is :

asked Dec 11, 2018 by pady_1

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Two masses $m_ = 5\; kg$ and $m_2 = 10 kg$ connected by an inextensible string over a frictionless pulley are moving as shown in the figure . The coefficient of friction of horizontal surface is 0.15. The minimum weight m that should be put on top of $m_2$ to stop the motion is :

asked Dec 11, 2018 by pady_1

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A particle is moving in a circular path of radius a under the action of an attractive potential $U = - \frac{k}{2r^2}$ . Its total energy is :

asked Dec 11, 2018 by pady_1

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Two batteries with e.m.f 12 V and 13 V are connected in paralled across a load resistor of $10 \Omega$ . The internal resistance of the two batteries are $1 \Omega$ and $2 \Omega$ respectively. The voltage across the load lies between :

asked Dec 11, 2018 by pady_1

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A solid sphere of radius r made of a soft material of bulk modulus K is surrounded by a liquid in a cylindrical container. A massless piston of area a floats on the surface of the liquid, covering entire cross section of cylindrical container. When a mass m is placed on the surface of the piston to compress the liquid, the fractional decrement in the radius of the sphere $(\frac{dr}{r})$ is

asked Dec 11, 2018 by pady_1

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The mass of a hydrogen molecule is $3.32 \times 10^{-27} kg$ . If $10^{23}$ hydrogen molecules strike, per second, a fixed wall of area $2\;cm^2$ at an angle of $45^{\circ}$ to the normal, and rebound elastically with a speed of $10^3 m/s$ , then the pressure on the wall is nearly :

asked Dec 11, 2018 by pady_1

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It is found that if a neutron suffers an elastic collinear collision with deuterium at rest, fractional loss of its energy is $p_d$ , while for its similar collision with carbon nucleus at rest, fractional loss of energy is $p_c$ . The values of $p_d$ and $p_c$ are respectively :

asked Dec 11, 2018 by pady_1

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Sodium salt of an organic acid 'X' produces effervescence with conc. $H_2SO_4$ . 'X' reacts with the acidified aqueous $CaCl_2$ solution to give a white precipitate which decolourises acidic solution of $KMnO_4$ . 'X' is :

asked Dec 11, 2018 by pady_1

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Which of the following, upon treatment with tert-BuONa followed by addition of bromine water, fails to decolourize the colour of bromine ?

asked Dec 11, 2018 by pady_1

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A water sample has ppm level concentration of following anions $F^- = 10, \; SO_4^{2-} = 100; \; NO_3^- = 50$ The anion/anions that make/makes the water sample unsuitable for drinking is/are :

asked Dec 11, 2018 by pady_1

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A metal crystallises in a face centred cubic structure. If the edge length of its unit cell is 'a', the closest approach between two atoms in metallic crystal will be :

asked Dec 11, 2018 by pady_1

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Which of the following reactions is an example of a redox reaction ?

asked Dec 11, 2018 by pady_1

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The major product obtained in the following reaction is :

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The radius of the second Bohr orbit for hydrogen atom is : (Planck's constant $h= 6.6262 \times 10^{-34} Js$ ; mass of electron = $9.1091 \times 10^{-31} kg$ ; charge of electron $e = 1.60210 \times 10^{-19}C$ ; permittivity of vacuum $\in_0 = 8.854185 \times 10^{-12} kg^{-1}m^{-3}A^{2}$ )

asked Dec 11, 2018 by pady_1

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The group having isoelectronic species is :

asked Dec 11, 2018 by pady_1

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Which of the following molecules is least resonance stabilized ?

asked Dec 11, 2018 by pady_1

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Two reactions $R_1$ and $R_2$ have identical pre-exponential factors. Activation energy of $R_1$ exceeds that of $R_2$ by $10\;kJ\; mol^{–1}$ . If $k_1$ and $k_2$ are rate constants for reactions $R_1$ and $R_2$ respectively at $300\; K$ , then $ln(k_2/k_1)$ is equal to : $(R = 8.314 \;J mol^{–1} K ^{–1} )$

asked Dec 11, 2018 by pady_1

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3-Methyl-pent-2-ene on reaction with HBr in presence of peroxide forms an addition product. The number of possible stereoisomers for the product is :

asked Dec 11, 2018 by pady_1

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Which of the following compounds will form significant amount of meta product during mono-nitration reaction ?

asked Dec 11, 2018 by pady_1

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The products obtained when chlorine gas reacts with cold and dilute aqueous NaOH are :

asked Dec 11, 2018 by pady_1

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The correct sequence of reagents for the following conversion will be :

asked Dec 11, 2018 by pady_1

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Both lithium and magnesium display several similar properties due to the diagonal relationship; however, the one which is incorrect, is :

asked Dec 11, 2018 by pady_1

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The increasing order of the reactivity of the following halides for the $S_N1$ reaction is :

asked Dec 11, 2018 by pady_1

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$pK_a$ of a weak acid (HA) and $pK_b$ of a weak base $(BOH)$ are $3.2$ and $3.4$ , respectively. The pH of their salt (AB) solution is :

asked Dec 11, 2018 by pady_1

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On treatment of $100 \;mL$ of $0.1 \;M$ solution of $CoCl_3.6H_2O$ with excess $AgNO_3;\; 1.2 \times 10^{22}$ ions are precipitated. The complex is :

asked Dec 11, 2018 by pady_1

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Which of the following species is not paramagnetic?

asked Dec 11, 2018 by pady_1

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The major product obtained in the following reaction is :

asked Dec 11, 2018 by pady_1

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Whcih of the following compounds will behave as a reducing sugar in an aqueous KOH solution?

asked Dec 11, 2018 by pady_1

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In the following reactions, $ZnO$ is respectively acting as a/an : (a) $ZnO + Na_2O \to Na_2ZnO_2$ (b) $ZnO + CO_2 \to ZnCO_3$

asked Dec 11, 2018 by pady_1

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The Tyndall effect is observed only when following conditions are satisfied : (a) The diameter of the dispersed particles is much smaller than the wavelength of the light used. (b) The diameter of the dispersed particles is not much smaller than the wavelength of the light used (c) The refractive indices of the dispersed phase and dispersion medium are almost similar in magnitude. (d) The refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude.

asked Dec 11, 2018 by pady_1

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Given : $E^{\circ}_{Cl_2/Cl^-} = 136 \; V, \; \; \; E^{\circ}_{Cr^{3+} / Cr} = -0.74 \; V$ $E^{\circ}_{Cr_2O_7^{2-}/Cr^{3+}} = 1.33\; V, \; \; \; E^{\circ}_{MnO_4^- / Mn^{2+}} = 1.51 \; V$ Among the following, the strongest reducing agent is :

asked Dec 11, 2018 by pady_1

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The formation of which of the following polymers involves hydrolysis reaction ?

asked Dec 11, 2018 by pady_1

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$\Delta U$ equal to :

asked Dec 11, 2018 by pady_1

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The most abundant elements by mass in the body of a healthy human adult are : Oxygen (61.4%); Carbon (22.9%), Hydrogen (10.0%) ; and Nitrogen (2.6%). The weight which a 75 kg person would gain if all $^1H$ atoms are replaced by $^2H$ atoms is :

asked Dec 11, 2018 by pady_1

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The freezing point of benzene decreases by $0.45^{\circ}C$ when $0.2\; g$ of acetic acid is added to $20 \;g$ of benzene. If acetic acid associates to form a dimer in benzene, percentage association of acetic acid in benzene will be : $(K_f$ for benzene = $5.12\; K \;kg\; mol^{–1} )$

asked Dec 11, 2018 by pady_1

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Given : $C_(graphite) + O_2(g) \to CO_2 (g) ; \; \; \; \; \Delta_r H^{\circ} = -393.5\; kJ \; mol^{-1};$ $H_2(g) + \frac{1}{2}O_2(g) \to H_2O(l); \;\;\;\; \; \; \; \; \Delta_rH^{\circ} = -285.8 \; kJ\; mol^{-1};$ $CO_2(g) + 2 H_2O (l) \to CH_4(g) + 2O_2 (g); \; \; \; \; \Delta_r H^{\circ} = + 890.3 \;kJ\; mol^{-1}$ Based on the above thermochemical equations, the value of $\Delta_r H^{\circ}$ at 298 K for the reaction

asked Dec 11, 2018 by pady_1

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1 gram of a carbonate $(M_2CO_3)$ on treatment with excess HCl produces $0.01186 \;mole$ of $CO_2$ . The molar mass of $M_2CO_3$ in $g\; mol^{–1}$ is :

asked Dec 11, 2018 by pady_1

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A body of mass $m = 10^{-2} kg$ is moving in a medium and experiences a frictional force $F= -kv^2$ . Its initial speed is $v_0 = 10\; ms^{-1}$ . If after 10 s, its energy is $\frac{1}{8} mv_0^2$ , the value of $k$ will be :

asked Dec 11, 2018 by pady_1

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A diverging lens with magnitude of focal length 25cm is placed at a distance of 15 cm from a converging lens of magnitude of focal length 20 cm. A beam of parallel light falls on the diverging lens. The final image formed is :

asked Dec 11, 2018 by pady_1

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An external pressure P is applied on a cube at $0^{\circ}C$ so that it is equally compressed from all sides. $K$ is the bulk modulus of the material of the cube and $\alpha$ is its coefficient of linear expansion. Suppose we want to bring the cube to its original size by heating. The temperature should be raised by :

asked Dec 11, 2018 by pady_1

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The variation of acceleration due to gravity g with distance d from centre of the earth is best represented by (R = Earth's radius)

asked Dec 11, 2018 by pady_1

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When a current of $5 \;mA$ is passed through a galvanometer having a coil of resistance $15 \; \Omega$ , it shows full scale defection. The value of the resistance to be put in series with the galvanometer to convert it into a voltmeter of range $0 – 10\; V$ is :

asked Dec 11, 2018 by pady_1

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