Recent questions tagged past papers

If the electric flux entering and leaving an enclosed surface respectively is $\phi_1$ and $\phi_2$, the electric charge inside the surface will be :

asked Dec 11, 2018 by pady_1

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Three forces start acting simultaneously on a particle moving with velocity $\overrightarrow{v}$. These forces are represented in magnitude and direcction by the three sides of a triangle ABC (as shown). The particle will now move with velocity :

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The physical quantities not having same dimensions are :

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An ammeter reads upto $1A$. Its internal resistance is $0.81 \Omega$. To increase the range to $10 \;A$, the value of the required shunt is:

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A boy playing on the roof of a 10 m high building throws a ball with a speed of 10 m/s at an angle of $30^{\circ}$ with the horizontal. How far from the throwing point will the ball be at the height of $10 \;m$ from the ground ? [$g = 10\; m/s^2, \; \sin 30^{\circ} = 1/2,\; \cos 30^{\circ} = \sqrt{3}/2]$

asked Dec 11, 2018 by pady_1

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A car moving with a speed of $50\; km/h$, can be stopped by brakes after at least $6 \;m$. If the same car is moving at a speed of $100\; km/h$, the minimum stopping distance is :

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The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the :

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Two spherical bodies of mass M and 5M and radii R and 2R respecitvely are released in free space with initial separation between their centres equal to 12 R. If they attract each other due to gravitational force only, then the distance covered by the smaller body just before collision is :

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When $U^{238}$ nucleus originally at rest, decays by emitting an alpha particle having a speed $u$, the recoil speed of the residual nucleus is :

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Which of the following radiations has the least wavelength ?

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A particle performing uniform circular motion has angular momentum L. If its angular frequency is doubled and its kinetic energy halved, then the new angular momentum is :

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The time period of a satellite of earth is 5 hours. If the separation between the earth and the satellite is increased to 4 times the previous value, the new time period will become :

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A circular disc $X$ of radius $R$ is made from an iron plate of thickess $t$, and another disc $Y$ of radius $4R$ is made from an iron plate of thickness $t/4$. Then the relation between the moment of inertia $I_X$ and $I_Y$ is :

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Dimensions of $\frac{1}{\mu_0 \varepsilon_0}$, where symbols have their usual meaning, are :

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The negative $Zn$ pole of Daniell cell, sending a constant current through a circuit, decreases in mass by $0.13\;g$ in $30$ minutes. If the electrochemical equivalent of $Zn$ and $Cu$ are $32.5$ and $31.5$ respectively, the increase in the mass of the positive $Cu$ pole in this time is :

asked Dec 11, 2018 by pady_1

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The thermo-emf of a thermocouple is $25 \; \mu V/^{\circ}C$ at room temperature. A galvanometer of $40 \Omega$ resistance, capable of detecting current as low as $10^{-5}A$, is connected with the thermocouple. The smallest temperature difference that can be detected by this system is :

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Consider telecommunication through optical fibres. Which of the following statements is not true ?

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A strip of copper and another of germanium are cooled from room temperature to 80 K. The resistance of :

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The length of a wire of a potentiometer is 100 cm, and the emf of its stand and cell is E volt. It is employed to measure the emf of a battery whose internal resistance is $0.5 \Omega$. If the balance point is obtained at $l = 30\; cm$ from the positive end, the emf of the battery is :

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A spring balance is attached to the ceiling of a lift. A man hangs his bag on the spring and the spring reads 49 N, when the lift is stationary. If the lift moves downward with an acceleration of 5 m/s, the reading of the spring balance will be :

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Curie temperature is the temperature above which :

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The magnetic lines of force inside a bar magnet :

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A magnetic needle lying parallel to a magnetic field requires $W$ unit of work to turn it through $60^{\circ}$. The torque needed to maintain the needle in this position will be :

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A thin rectangular magnet suspended freely has a period of oscillation equal to $T$. Now it is broken into two equal halves (each having half of the original length) and one piece is made to oscillate freely in the same field. If its period of oscillation is $T'$, the ratio $T'/T$ is :

asked Dec 11, 2018 by pady_1

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A particle of charge $-16 \times 10^{-18} C$ moving with velocity $10\; ms^{-1}$ along the x-axis enters a region where a magnetic field of induction B is along the y-axis and an electric field of magnitude $10^4 V/m$ is along the negative z-axis. If the charged particle continues moving along the x-axis, the magnitude of B is :

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A particle of mass $M$ and charge $Q$ moving with velocity $\overrightarrow{v}$ describes a circular path of radius $R$ when subjected to a uniform transverse magnetic field of induction $B$. The work done by the field when the particle completes one full circle is :

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According to molecular orbital theory, which of the following will not be a viable molecule ?

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For 1 molal aqueous solution of the following compounds, which one will show the highest freezing point ?

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Which of the following compounds contain(s) no covalent bond(s) ? $KCl, \; PH_3,\; O_2, \; B_2H_6, \;H_2SO_4$

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Which of the following are Lewis acids?

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The combustion of benzene $(l)$ gives $CO_2(g)$ and $H_2O (l)$. Given that heat of combustion of benzene at constant volume is $-3263.9 \; kJ\; mol^{-1}$ at $25^{\circ}C$; heat of combustion (in $kJ\; mol^{-1}$) of benzene at constant pressure will be - $(R = 8.314 \;JK^{-1} mol^{-1})$

asked Dec 11, 2018 by pady_1

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Which type of 'defect' has the presence of cations in the interstitial sites ?

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The oxidation states of $Cr$ in $[Cr(H_2O)_6]Cl_3, [Cr(C_6H_6)_2]$, and $K_2[Cr(CN)_2(O)_2(O_2)(NH_3)]$ respectively are :

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The predominant form of histamine present in human blood is ($pK_a$ , Histidine = 6.0)

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The compound that does not produce nitrogen gas by the thermal decomposition is :

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The recommended concentration of fluoride ion in drinking water is up to 1 ppm as fluoride ion is required to made teeth enamel harder by converting $ [3Ca_3(PO_4)_2.Ca(OH)_2]$ to:

asked Dec 11, 2018 by pady_1

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An aqueous solution contains $0.10\; M \;H_2S$ and $0.20\; M \; HCl$. If the equilibrium constant for the formation of $HS^-$ from $H_2S$ is $1.0 \times 10^{-7}$ and that of $S^{2-}$ from $HS^-$ ions is $1.2 \times 10^{-13}$ then the concentration of $S^{2-}$ ions in aqueous solution is :

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When metal 'M' is treated with NaOH, a white gelatinous precipitate 'X' is obtained, which is soluble in excess of NaOH. Compound 'X' when heated strongly gives an oxide which is used in chromatography as an adsorbent. The metal M is :

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Which of the following compounds will be suitable for Kjeldahl's method for nitrogen estimation ?

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An aqueous solution contains an unknown concentration of $Ba^{2+}$. When $50\; mL$ of the $1M$ solution of $Na_2SO_4$ is added, $BaSO_4$ just begins to precipitate. The final volume is $500\; mL$. The solubility product of $BaSO_4$ is $1 \times 10^{-10}$. What is the original concentration of $Ba^{2+}$.

asked Dec 11, 2018 by pady_1

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Phenol on treatment with $CO_2$ in the presence of $NaOH$ followed by acidification produces a compound $X$ as the major product. $X$ on treatment with $(CH_3 CO_2)O$ in presence of catalytic amount of $H_2SO_4$ produced :

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The major product of the following reaction is :

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Consider the following reaction and statements : $[Co(NH_3)_4Br_2]^+ + Br^- \to [Co(NH_3)_3Br_3] + NH_3$ (i) Two isomers are produced if the reactant complex ion is a cis-isomer. (ii) Two isomers are produced if the reactant complex ions is a trans-isomer. (iii) Only one isomer is produced if the reactant complex ion is a trans-isomer. (iv) Only one isomer is produced if the reactant complex ion is a cis-isomer. The correct statements are :

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Glucose on prolonged heating with $HI$ gives :

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At $518^{\circ}C$, the rate of decomposition of a sample of gaseous acetaldehyde, initially at a pressure of $363 $ Torr, was $1.00 \; Torr\;s^{-1}$ when $5\%$ had reacted and $0.5\; Torr\; s^{-1}$ when $33\%$ had reacted. The order of the reaction is :

asked Dec 11, 2018 by pady_1

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Which of the following lines correctly show the temperature dependence of equilibrium constant $K$, for an exothermic reaction ?

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How long (approximate) should water be electrolysed by passing through 100 amperes current so that the oxygen released can completely burn 27.66 g of diborane ? (Atomic weight of B = 10.8 u)

asked Dec 11, 2018 by pady_1

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The major product formed in the following reaction is :

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Hydrogen peroxide oxidises $[Fe(CN)_6]^{4-}$ to $[Fe(CN)_6]^{3-}$ in acidic medium but reduces $[Fe(CN)_6]^{3-}$ to $[Fe(CN)_6]^{4-}$ in alkaline medium. The other products formed are, respectively.

asked Dec 11, 2018 by pady_1

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The ratio of mass percent of $C$ and $H$ of an organic compound $(C_XH_YO_Z)$ is $6:1$. If one molecule of the above compound $(C_XH_YO_Z)$ contains half as much oxygen as required to burn one molecule of compound $C_XH_Y$ completely to $CO_2$ and $H_2O$. The empirical formula of compound $C_XH_YO_Z$ is :

asked Dec 11, 2018 by pady_1

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