Recent questions tagged class12

The below reaction involves

asked Feb 19, 2014 by sreemathi.v

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The correct order of reactivities of nucleophilic addition across -C=O of the RCOR ,RCHO and ArCHO is

asked Feb 19, 2014 by sreemathi.v

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Which of the following species is an intermediate in the reaction shown below :

asked Feb 19, 2014 by sreemathi.v

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The refractive index of a prism is 2. This prism can have a maximum refracting angle of

asked Feb 19, 2014 by meena.p

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Two concentric shells have radii R & 2R , charges $\;q_{A}\;and\;q_{B}\;$ and potential 2V and $\;\large\frac{3}{2} V\;$ respectively . Now shell B is earthed and let charges on them becomes $\;q_{A}^{|}\;and\;q_{B}^{|}\;.$ Then $\;\large\frac{q_{A}^{|}}{q_{A}}+\large\frac{q_{B}^{|}}{q_{B}}\;$ is

asked Feb 19, 2014 by yamini.v

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A glass sphere with radius 10 cm has concentric spherical equity of radius 5 cm. A narrow beam of parallel light is directed into sphere, as shown . Find the position of final image from centre of sphere

asked Feb 19, 2014 by meena.p

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A large metal sheet carries an electric current along its surface with $ \lambda$ being the current per unit length. The value of the magnetic field near the surface of the sheet is

asked Feb 19, 2014 by thanvigandhi_1

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The reduction at acetone with magnesium amalgam followed by hydrolysis produces

asked Feb 19, 2014 by sreemathi.v

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The electric potential at a point $\;(x , y)\;$ in the x- y plane is given by $\;V=-k\;x\;y\;$. The field intensity at a distance r in this plane , from the origin is proportional to

asked Feb 19, 2014 by yamini.v

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There exists uniform electric and magnetic fields in space. A particle is moving with a velocity $ \overrightarrow v$ and suddenly a hollow metallic cube is enclosed around it. The change in force exerted on the particle is

asked Feb 19, 2014 by thanvigandhi_1

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Two parallel wires carrying equal currents in the opposite directions are placed at $x = \pm$ a parallel to the $y$-axis with $z = 0$. Magnetic field at origin $O$ is $B1$ and at $P (2a,0,0)$ is $B2$. Then the ratio $ \large\frac{B1}{B2}$ is

asked Feb 19, 2014 by thanvigandhi_1

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A wire of length $1m$ is placed in $x-z$ plane carries a current of $1A$. The coefficient of friction between the wire and the surface is $0.2$ and the mass of the wire is $2\; Kg$. The magnetic field of strength $2T$ exists along positive $y$ direction. Then which of the following is correct

asked Feb 19, 2014 by thanvigandhi_1

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A charged particle enters a magnetic field at right angles to the magnetic field. The field exists for a length equal to 1.5 times the radius of the circular path of the particle. The particle will deviate from its path by

asked Feb 19, 2014 by thanvigandhi_1

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The haloform reaction is not shown by the compound

asked Feb 19, 2014 by sreemathi.v

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Ratio of the magnetic field at the centre of a current carrying coil of radius $R$ and at a distance of $3R$ on its axis is

asked Feb 19, 2014 by thanvigandhi_1

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A uniform magnetic field $ \overrightarrow B = B_0\hat j$ exists in space. A particle of mass $m$ and charge $q$ is projected towards negative $x$-axis with speed $v$ from a point $(d,0,0)$. The maximum value of $v$ for which the particle does not hit the $y-z$ plane is

asked Feb 19, 2014 by thanvigandhi_1

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An observer can see through a pin hole the top end of a thin rod of height h, placed as shown. The beaker height is 3 h and its radius is h. When the beaker is filled with a liquid up to a height 2h ,he can see the lower end of the rod. Then RI of liquid is .

asked Feb 19, 2014 by meena.p

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An electron is moving along positive $ x$-axis. A uniform electric field exists along negative $y$-axis. What should be the direction of the magnetic field (constant) so that the force on the electron is zero?

asked Feb 19, 2014 by thanvigandhi_1

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A copper wire of diameter $1.6mm$ carries a current i. The maximum magnetic field due to this wire is $5 \times 10^{-3} T$. The value of $i$ is

asked Feb 19, 2014 by thanvigandhi_1

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Refer the below reaction :

asked Feb 19, 2014 by sreemathi.v

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Figure shows a closed dotted surface which intersects a conducting uncharged sphere . If a +ve charge is placed at the point P, the flux of the electric field through the closed surface

asked Feb 19, 2014 by yamini.v

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A proton beam is going from north to south and an electron beam is going from south to north. Neglecting the earth’s magnetic field, the electron beam will be deflected (consider only magnetic forces)

asked Feb 19, 2014 by thanvigandhi_1

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Two beam of light having intensities $I$ and $4I$ interfere to produce a fringe pattern on a screen . The phase difference between beams is $ \large\frac{\pi}{2}$ at point A and n at point B. Then the difference between resultant intensities at A and B is

asked Feb 19, 2014 by meena.p

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There are two uncharged identical metallic spheres 1 and 2 of radius r separated by a distance d (d > > r) . $\;\lambda\;$ charged metallic sphere of same radius having charge q is touched with one of the sphere . After some time it is moved away from the system . Now the uncharged sphere is earthed . Charge on earthed sphere is

asked Feb 19, 2014 by yamini.v

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Refer the below :

asked Feb 19, 2014 by sreemathi.v

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Which of the following compounds does not under go aldol condensation?

asked Feb 19, 2014 by sreemathi.v

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Which of the following statements regarding aldehyde is not correct?

asked Feb 19, 2014 by sreemathi.v

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A non-conducting disc of radius a and uniform +ve surface charge density $\; \sigma\;$ is placed on the ground with it 's axis vertical . A particle of mass m and +ve charge q is dropped , along the axis of the disc from a height H with zero initial velocity . Find the value of H if the particle just reaches the disk .$\;\large\frac{q}{m}=4 \in_{0} g/\sigma$ . Find the position of particle at which the particle is in equilibrium. Find the energy of the particle at $\;H=\large\frac{a}{\sqrt{3}}\;$ assuming the gravitational energy at $\;H=0\;$ to be zero

asked Feb 19, 2014 by yamini.v

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In a YDSE , 12 fringes are observed to be formed in a certain segment of screen when light of wavelength $600\; nm$ is used. If the wavelength of length is changed to $400\; nm$ , number of fringes observed in same segment of screen in given by

asked Feb 19, 2014 by meena.p

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A ray of light falls on a transparent glass slab with refractive index (relative to air) of $1.62$ . The angle of incident for which the reflected and refractive rays are mutually perpendicular is :

asked Feb 19, 2014 by meena.p

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When a beam of light with wave length $\lambda= 6000 A, $ travelling in air, enters a glass medium whose refractive index is 1.5 then,

asked Feb 19, 2014 by meena.p

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A non-conducting disc of radius a and uniform +ve surface charge density $\; \sigma\;$ is placed on the ground with it 's axis vertical . A particle of mass m and +ve charge q is dropped , along the axis of the disc from a height H with zero initial velocity . Find the value of H if the particle just reaches the disk .$\;\large\frac{q}{m}=4 \in_{0} g/\sigma$ . Find the position of particle at which the particle is in equilibrium

asked Feb 18, 2014 by yamini.v

1 answer

A non-conducting disc of radius a and uniform +ve surface charge density $\; \sigma\;$ is placed on the ground with it 's axis vertical . A particle of mass m and +ve charge q is dropped , along the axis of the disc from a height H with zero initial velocity . Find the value of H if the particle just reaches the disk .$\;\large\frac{q}{m}$$=4 \in_{0} g/\sigma$

asked Feb 18, 2014 by yamini.v

1 answer

Two lenses , One concave and the other convex of same power are placed such that their principal axes coincide. If the separation b/w the lenses is x, then ,

asked Feb 18, 2014 by meena.p

1 answer

A $16\;cm$ long image of an object is formed by a convex lens on a screen. On moving the lens towards the screen with out changing the positions of object an image of size 9 cm is again formed again on the screen . The size of object is

asked Feb 18, 2014 by meena.p

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A thin equiconvex lens of refractive index $\large\frac{3}{2}$ and radius of curvature 30 m is put in water $(RI= \large\frac{4}{3})$. Its focal length is

asked Feb 18, 2014 by meena.p

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The number of all possible matrices of order 3 x 3 with each entry 0 or 1 is?

asked Feb 18, 2014 by balaji.thirumalai

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A lens of focal length f projects m times magnified image of an object on a screen.The distance of screen from lens is

asked Feb 18, 2014 by meena.p

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The region between two concentric shells of radii a and b $\;(b > a)\;$ contains volume charge density $\;\rho(r)=\large\frac{C}{r}\;$ , where C is a constant and r is the radial distance , as shown in figure . A point charge q is placed at the origin , r=0 . Find the value of C for which the electric field in the region between the spheres is constant.

asked Feb 18, 2014 by yamini.v

1 answer

A rectangular tank of mass $\;m_{0}\;$ and charge Q over it is placed over a smooth horizontal floor. A horizontal electric field E exist in the region . Rain drops are falling vertically in the tank at the constant rate of n drops per second . Mass of each drop is m . find velocity of tank as function of time .

asked Feb 18, 2014 by yamini.v

1 answer

The maximum electric field intensity inside a sphere of radiusR is

asked Feb 18, 2014 by yamini.v

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A ray of light passes through an equilateral prism such that the angle of incidence and the angle of emergence are equal to $\large\frac{3}{4}th$ of the angle of prism. The angle of minimum deviation is

asked Feb 18, 2014 by meena.p

1 answer

The cannizzaro reaction is not given by

asked Feb 18, 2014 by sreemathi.v

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The point $\;r_{m}\;$ inside the sphere of a sphere of radius R at which electric field intensity is maximum , is given by

asked Feb 18, 2014 by yamini.v

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The magnitude of the electric field as a function of the distance r outside the ball is given by

asked Feb 18, 2014 by yamini.v

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A ray of light traveling in a transparent medium falls on a surface separating the medium from air at an angle of incidence of $45^{\circ}$ The ray undergoes total internal reflection . If n is the refractive index of medium with respect to air, select the possible value of n from following

asked Feb 18, 2014 by meena.p

1 answer

In the Cannizzaro reaction given : $2C_6H_5-CHO\quad \underrightarrow {OH^-}\quad C_6H_5-CH_2OH +C_6H_5COO^-$ the slowest step is

asked Feb 18, 2014 by sreemathi.v

1 answer

A diminished image of an object is to be obtained on a screen 1. m away from it . This can be achieved by approximately placing.

asked Feb 18, 2014 by meena.p

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Which of the following is an example of aldol condensation?

asked Feb 18, 2014 by sreemathi.v

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A ray of light passes through four transparent media with refractive indices $\mu_1,\mu_2,\mu_3$ of all media are parallel, If the emergent ray CD is parallel ti incident ray AB. We must have

asked Feb 18, 2014 by meena.p

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