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If a, b, c, d are inputs to a gate and x is its output, then, as per the following time graph, the gate is :

asked Mar 7, 2017 by meena.p

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Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes, respectively.Initially, the samples have equal number of nuclei. After 80 minutes, the ratio of decayed numbers of A and B nuclei will be:

asked Mar 7, 2017 by meena.p

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Radiation of wavelength $\lambda$ , is incident on a photocell. The fastest emitted electron has speed v. If the wavelength is changed to $\large\frac{3 \lambda}{4}$, the speed of the fastest emitted electron will be :

asked Mar 7, 2017 by meena.p

1 answer

The box of a pin hole camera, of length $L$, has a hole of radius a. It is assumed that when the hole is illuminated by a parallel beam of light of wavelength $\lambda$ the spread of the spot (obtained on the opposite wall of the camera) is the sum of its geometrical spread and the spread due to diffraction. The spot would then have its minimum size (say $b_{min}$) when :

asked Mar 7, 2017 by meena.p

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An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20. To the observer the tree appears :

asked Mar 6, 2017 by meena.p

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Arrange the following electromagnetic radiations per quantum in the order of increasing energy : <br> A : Blue light B : Yellow light C : X-ray D : Radiowave

asked Mar 6, 2017 by meena.p

1 answer

An arc lamp requires a direct current of 10 A at $80\; V$ to function. It is connected to a $220 \;V(rms), 50\; Hz$ AC supply, the series inductor needed for it to work is close to :

asked Mar 6, 2017 by meena.p

1 answer

Hysteresis loops for two magnetic materials A and B are given below : These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then it is proper to use :

asked Mar 6, 2017 by meena.p

1 answer

Two identical wires A and B, each of length ‘l ’, carry the same current I. Wire A is bent into a circle of radius R and wire B is bent to form a square of side ‘a’. If $B_A$ and $B_B$ are the values of magnetic field at the centres of the circle and square respectively, then the ratio $\large\frac{B_A}{B_B}$ is :

asked Mar 6, 2017 by meena.p

1 answer

The temperature dependence of resistances of $Cu$ and undoped Si in the temperature range $300 - 400 K$ , is best described by :

asked Mar 6, 2017 by meena.p

1 answer

A combination of capacitors is set up as shown in the figure. The magnitude of the electric field due to a point charge Q (having a charge equal to the sum of the charges on the $4 \mu F$ and $9 \mu F$ capacitors), at a point distant $30\; m$ from it, would equal :

asked Mar 6, 2017 by meena.p

1 answer

The region between two concentric spheres of radii $‘a’$ and $‘b’$, respectively (see figure), has volume charge density $\rho = \large\frac{A}{r}$, where A is a constant and r is the distance from the centre. At the centre of the spheres is a point charge Q. The value of A such that the electric field in the region between the spheres will be constant, is :

asked Mar 6, 2017 by meena.p

1 answer

A uniform string of length $20\;m$ is suspended from a rigid support. A short wave pulse in introduced at its lowest end. It starts moving up the string. The time taken to reach the support is : (take $g=10\;ms^{-2})$

asked Mar 6, 2017 by meena.p

1 answer

A particle performs simple harmonic motion with amplitude A. Its speed is trebled at the instant that it is at a distance $\large\frac{2A}{3}$ from equilibrium position. The new amplitude of the motion is :

asked Mar 2, 2017 by meena.p

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‘n’ moles of an ideal gas undergoes a process $A \to B$ as shown in the figure. The maximum temperature of the gas during the process will be :

asked Mar 2, 2017 by meena.p

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An ideal gas undergoes a quasi static, reversible process in which its molar heat capacity Cremains constant. If during this process the relation of pressure P and volume V is given by $PV^n= constant$, then n is given by (Here $C_P$ and $C_V$ are molar specific heat at constant pressure and constant volume, respectively) :

asked Mar 2, 2017 by meena.p

1 answer

A pendulum clock loses $12\;s$ a day if the temperature is $40 ^{\circ} C $ and gains $4s\;a$ day if the temperature is $20 ^{\circ}C$. The temperature at which the clock will show correct time, and the co-efficient of linear expansion $(\alpha)$ of the metal of the pendulum shaft are respectively :

asked Mar 2, 2017 by meena.p

1 answer

A satellite is revolving in a circular orbit at a height ‘h’ from the earth’s surface (radius of earth R; $h << R$ ). The minimum increase in its orbital velocity required, so that the satellite could escape from the earth’s gravitational field, is close to : (Neglect the effect of atmosphere).

asked Mar 2, 2017 by meena.p

1 answer

A roller is made by joining together two cones at their vertices O.It is kept on two rails AB and CD which are placed asymmetrically (see figure), with its axis perpendicular to CD and its centre O at the centre of line joining AB and CD (see figure). It is given a light push so that it starts rolling with its centre O moving parallel to CD in the direction shown. As it moves, the roller will tend to :

asked Mar 2, 2017 by meena.p

1 answer

A person trying to lose weight by burning fat lifts a mass of $10\; kg$ upto a height of $1\; m\; 1000\;times$.Assume that the potential energy lost each time he lowers the mass is dissipated. How much fat will he use up considering the work done only when the weight is lifted up? Fat supplies $3.8 \times 10^7\;J$ of energy per kg which is converted to mechanical energy with a $20\%$ efficiency rate. Take $g = 9.8 ms^{-2}$:

asked Mar 1, 2017 by meena.p

1 answer

A point particle of mass $m$, moves along the uniformly rough track $PQR$ as shown in the figure.The coefficient of friction, between the particle and the rough track equals $\mu$. The particle is released, from rest, from the point P and it comes to rest at a point R. The energies, lost by the ball, over the parts, PQ and QR, of the track, are equal to each other, and no energy is lost when particle changes direction from PQ to QR.The values of the coefficient of friction $\mu$ and the distance $x (= QR),$ are, respectively close to :

asked Mar 1, 2017 by meena.p

1 answer

A particle of mass m is moving along the side of a square of side $‘a’$, with a uniform speed $v$ in the $x-y$ plane as shown in the figure : Which of the following statements is false for the angular momentum $\overrightarrow {L}$ about the origin?

asked Mar 1, 2017 by meena.p

1 answer

A student measures the time period of $100$ oscillations of a simple pendulum four times. The data set is $90\; s, 91\; s, 95\; s\; and\; 92\; s$. If the minimum division in the measuring clock is $1\; s$, then the reported mean time should be :

asked Mar 1, 2017 by meena.p

1 answer

From the following statements regarding $H_2O_2$ , choose the incorrect statement :

asked Nov 18, 2015 by meena.p

1 answer

The following reaction is performed at $298\;K$

asked Nov 18, 2015 by meena.p

1 answer

Which polymer is used in the manufacture of paints and lacquers ?

asked Nov 18, 2015 by meena.p

1 answer

Which one has the highest boiling point ?

asked Nov 18, 2015 by meena.p

1 answer

Assertion : Nitrogen and Oxygen are the main component in the atmosphere but these but these do not react to form oxides of nitrogen . Reason : The reaction between nitrogen and Oxygen requires high temperature .

asked Nov 18, 2015 by meena.p

1 answer

The standard Gibbs energy changes at 300 k for the reaction $2A= B+C$ is $2494.2\;J$ At a given time, the composition of the reaction mixture is $[A]=\large\frac{1}{2}$$,[B] =24$ and $[C]=\frac{1}{2} $. The reaction proceeds in the : $[R= 8.314\;J/K/mol,e = 2.718]$

asked Nov 18, 2015 by meena.p

1 answer

Which among the following

asked Nov 18, 2015 by meena.p

1 answer

The Vapour pressure of acetone at $20^{\circ}C$ is $185\;torr$.When $1.2 \;g$ of a non- volatile substance was dissolved in 100 g of acetone at $20^{\circ}$its vapour pressure was $183$ torr. The molar mass $(g mol^{-1}) of the substance is :

asked Nov 18, 2015 by meena.p

1 answer

3g of activated charcoal was added to 50 mL of acetic acid solution $(0.06\;N)$ in a flask. After an hour it was filtered was found to be $0.042\;N$ . The amount of acetic acid absorbed (per gram of charcoal ) is :

asked Nov 18, 2015 by meena.p

1 answer

The synthesis of alkyl fluorides is best accomplished by :

asked Nov 18, 2015 by meena.p

1 answer

The color of $kMnO_4$ is due to

asked Nov 18, 2015 by meena.p

1 answer

In Carius method of estimation of halogens, $250\;mg$ of an organic compound gave $141\;mg$ of $AgBr$. The percentage of bromine in the compound is

asked Nov 18, 2015 by meena.p

1 answer

The number of geometric isomers that can exist for square planar $[Pt(Cl)(py)(NH_3)(NH_2OH)] +$ (py= pyridine ):

asked Nov 17, 2015 by meena.p

1 answer

Two Faraday of electricity is passed through a solution of $CuSO_4$ . The mass of copper deposited at the cathode is : (at . mass of Cu=63.5 amu)

asked Nov 17, 2015 by meena.p

1 answer

The molecular formula of a commercial resin used for exchanging ions in water softening is $C_8H_7SO_3Na$ (Mol.wt.206) What would be the maximum uptake of $Ca^{2+}$ ions by the resin when expressed in mole per gram resin ?

asked Nov 17, 2015 by meena.p

1 answer

The inter molecular interaction that is dependent on the inverse cube of distance between the molecules is :

asked Nov 17, 2015 by meena.p

1 answer

Match the catalysts to the correct processes :

asked Nov 17, 2015 by meena.p

1 answer

Which of the following compounds will exhibit geometrical isomerism?

asked Nov 17, 2015 by meena.p

1 answer

Higher order $(>3)$ reactions are rare due to :

asked Nov 17, 2015 by meena.p

1 answer

In the following sequence of reaction :

asked Nov 17, 2015 by meena.p

1 answer

In the context of the Hall- Heroult process for the extraction of $Al$ which of the following statement is false ?

asked Nov 17, 2015 by meena.p

1 answer

The ionic radii (in A) of $N^{3-},O^{2-}$ and $F^{-}$ are respectively :

asked Nov 17, 2015 by meena.p

1 answer

Which of the following compounds is not an antacid ?

asked Nov 17, 2015 by meena.p

1 answer

Which of the following is the energy of a possible excited state of hydrogen ?

asked Nov 17, 2015 by meena.p

1 answer

Which of the following compounds is not colored yellow ?

asked Nov 17, 2015 by meena.p

1 answer

Sodium metal crystallizes in a body centered cubic lattice with a unit cell edge of $44.29 \dot{A}$ the radius of sodium atom is approximately :

asked Nov 17, 2015 by meena.p

1 answer

In the reaction

asked Nov 17, 2015 by meena.p

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