Recent questions in 2007

For a cubic crystal structure which one of the following relations indicting the cell characteristic is correct :-

asked Jul 26, 2018 by pady_1

2 answers

In the following circuit, the output Y for all possible inputs A and B is expresed by the truth table :-

asked Jul 26, 2018 by pady_1

1 answer

A common emitter amplifier has voltage gain of 50, an input impedance of 100 $\Omega$ and an output impedance of 200 $\Omega$. The power gain of the amplifier is :-

asked Jul 26, 2018 by pady_1

1 answer

In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is :- <img src""/>

asked Jul 26, 2018 by pady_1

1 answer

The total energy of electron in the ground state of hydrogen atom is -13.6 eV. The kinetic energy of an electron in first excited state is :-

asked Jul 26, 2018 by pady_1

2 answers

Two radioactive substances A and B have decay constants $5 \lambda$ and $\lambda $ respectively. At $t=0$ they have the same number of nuclei. The ratio of number of nuclei of A to those of B will be $(\frac{1}{e} )^2$ after a time interval :-

asked Jul 26, 2018 by pady_1

1 answer

A nucleus $^A_Z X$ has mass represented by $M(A,Z)$. If $M_p$ and $M_n$ denote the mass of proton and neutron respectively and B.E. the binding energy in MeV, then:

asked Jul 26, 2018 by pady_1

1 answer

In radioactive decay process, the negatively charged emitted $\beta$- particles are :-

asked Jul 26, 2018 by pady_1

1 answer

If the nucleus $^{27}_{13}Al$ has a nuclear radius of about 3.6 fm, the $^{125}_{52}Te$ would have its radius approximately as :-

asked Jul 26, 2018 by pady_1

1 answer

In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular paths of radius R using a magnetic field B. If V and B are kept constant, the ratio $\frac{Charge\; on\; the ion}{mass\; of\; the\; ion}$ will be proportional to :-

asked Jul 26, 2018 by pady_1

1 answer

Monochromatic light of frequency $6.0 \times 10^{14}$ Hz is produced by a laser. The power emitted is $2 \times 10^{-3}$W. The number of photons emitted, on the average, by the source per second is :-

asked Jul 26, 2018 by pady_1

1 answer

A 5 watt source emits monochromatic light of wavelength 5000 Å. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0m, the number of photo electrons liberated will :

asked Jul 26, 2018 by pady_1

1 answer

Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature then it will show :-

asked Jul 26, 2018 by pady_1

1 answer

A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately-

asked Jul 26, 2018 by pady_1

1 answer

What is the value of inductance L for which the current is a maximum in a series LCR circuit with $C = 10 \mu F$ and $\omega = 1000^{-1}$

asked Jul 26, 2018 by pady_1

1 answer

The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux $\phi$ linked with the primary coil is given by $\phi = \phi_0 + 4t$, where $\phi$ is in webers, t is time in seconds and $\phi_0$ is a constant, the output voltage across the secondary coil is :

asked Jul 26, 2018 by pady_1

1 answer

A beam of electrons passes undeflected through mutually perpendicular electric and magnetic fields. It the electric field is switched off, and the same magnetic field is maintained, the electrons move :

asked Jul 26, 2018 by pady_1

1 answer

A charged particle (charge q) is moving in a circle of radius R with uniform speed v. The associated magnetic moment $\mu$ is given by:

asked Jul 26, 2018 by pady_1

1 answer

Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius R with constant speed v. The time period of the motion-

asked Jul 26, 2018 by pady_1

1 answer

The resistance of an ammeter is $13 \Omega $ and its scale is graduated for a current upto $100$ amps. After and additional shunt has been connected to this ammeter it becomes possible to measure currents upto $750$ amperes by this meter. The value of shunt-resistance is-

asked Jul 26, 2018 by pady_1

1 answer

Three resistances P, Q, R each of $2 \Omega$ and an unknown resistance S form the four arms of a Wheatstone bridge circuit. When a resistance of $6 \Omega$ is connected in parallel to S the bridge gets balanced. What is the value of S ?

asked Jul 26, 2018 by pady_1

1 answer

If the cold junction of a thermo-couple is kept at $0^{\circ}C$ and the hot junction is kept at $T^{\circ}C$, then the relation between neutral temperature $(T_n)$ and temperature of inversion $(T_i)$ is:

asked Jul 26, 2018 by pady_1

1 answer

A steady current of $1.5$ amp flows through a copper voltameter for 10 minutes. If the electrochemical equivalent of copper is $30 \times 10^{–5}$ gm $coulomb^{–1}$, the mass of copper deposited on the electrode will be: -

asked Jul 26, 2018 by pady_1

1 answer

The total power dissipated in watts in the circuit shown here is :-

asked Jul 26, 2018 by pady_1

1 answer

Two condensers, one of capacity $C$ and the other of capacity $\frac{C}{2}$ , are connected to a V-volt battery, as shown- The work done in charging fully both the condensers is :

asked Jul 26, 2018 by pady_1

1 answer

Three point charges +q, –2q and +q are placed at points (x = 0, y = a, z = 0), (x = 0,y = 0, z = 0) and (x = a, y = 0, z = 0) respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are:-

asked Jul 26, 2018 by pady_1

1 answer

A hollow cylinder has a charge q coulomb within it. If $\phi$ is the electric flux in units of voltmeter associated with the curved surface B, the flux linked with the plane surface A in units of voltmeter will be- <img src =""/>

asked Jul 26, 2018 by pady_1

1 answer

Charge +q and â€“q are placed at points A and B respectively which are at distance $2L$ apart, C is the midpoint between A and B. The work done in moving a charge + Q along the semicircle CRD is:-

asked Jul 26, 2018 by pady_1

1 answer

A small coin is resting on the bottom of a beaker filled with a liquid. A ray of light from the coin travels upto the surface of the liquid and moves along its surface (see figure) How fast is the light traveling in the liquid ?

asked Jul 26, 2018 by pady_1

1 answer

The electric and magnetic field of an electromagnetic wave are:-

asked Jul 26, 2018 by pady_1

1 answer

A particle executes simple harmonic oscillation with an amplitude a. The period of oscillation is T. The minimum time taken by the particle to travel half of the amplitude from the equilibrium position is:

asked Jul 26, 2018 by pady_1

1 answer

The particle executing simple harmonic motion has a ienetic energy $K_0 \cos^2 ωt$. The maximum values of the potential energy and the total energy are respectively:-

asked Jul 26, 2018 by pady_1

1 answer

The phase difference between the instantaneous velocity and acceleration of a particle executing simple harmonic motion is :-

asked Jul 26, 2018 by pady_1

1 answer

The frequency of a light wave in a material is $2 \times 10^{14}$ Hz and wavelength is $5000$ Å. The refractive index of material will be:-

asked Jul 26, 2018 by pady_1

1 answer

A black body is at $727^{\circ}C$. It emits energy at a rate which is proportional to:

asked Jul 26, 2018 by pady_1

1 answer

An engine has an efficiency of $1/6$. When the temperature of sink is reduced by $62^{\circ}C$, its efficiency is doubled. Temperature of the source is-

asked Jul 26, 2018 by pady_1

1 answer

Assuming the sun to have a spherical outer surface of radius $r$, radiating like a black body at temperature $t^{\circ}$C, the power received by a unit surface, (normal to the incident rays) at distance $R$ from the centre of the Sun is Where $\sigma$ is the Stefan's Contant :-

asked Jul 26, 2018 by pady_1

1 answer

Two satellites of earth, $S_1$ and $S_2$, are moving in the same orbit. The mass of $S_1$ is four times the mass of $S_2$. Which one of the following statements is true ?

asked Jul 26, 2018 by pady_1

2 answers

A uniform rod AB of length $l$ and mass $m$ is free to rotate about point $A$. The rod is released from rest in the horizontal position. Given that the moment of inertia of the rod about $A$ is $\frac{ml^2}{3}$,the initial angular acceleration of the rod will be <img src =" "/>

asked Jul 26, 2018 by pady_1

2 answers

A particle of mass $m$ moves in the XY plane with a velocity v along the straight line $AB$. If the angular momentum of the particle with respect to origin $O$ is $L_A$ when it is at $A$ and $L_B$ when it is at $B$, then : <img src =""/>

asked Jul 26, 2018 by pady_1

1 answer

A mass of $2.0 kg$ is put on a flat pan attached to a vertical spring fixed on the ground as shown in the figure. The mass of the spring and the pan is negligible. When pressed slightly and released the mass executes a simple harmonic motion. The spring constant is $200N/m$. What should be the minimum amplitude of the motion so that the mass gets detached from the pan (Take $g = 10 m/s^2$) <img src =""/>

asked Jul 26, 2018 by pady_1

1 answer

The position $x$ of a particle with respect to time $t$ along x-axis is given by $x = 9t^2 – t^3$ where $x$ is in metres and $t$ in seconds. What will be the position of this particle when it achieves maximum speed along the + x direction ?

asked Jul 26, 2018 by pady_1

1 answer

$\overrightarrow{A}$ and $\overrightarrow{B} $ are two vectors and $\theta$ is the angle between them, if $| \overrightarrow{A} \times \overrightarrow{B} | = \sqrt{3} (\overrightarrow{A}.\overrightarrow{B})$ the value of $\theta$ is:-

asked Jul 26, 2018 by pady_1

1 answer

A wheel as angular acceleration of $3.0 rad/sec^2$ and initial angular speed of $2.00 rad/sec$. In a time of $2 sec$ it has rotated through an angle (in radian) of :

asked Jul 26, 2018 by pady_1

1 answer

A vertical spring with force constant K is fixed on a table. A ball of mass m at a height h above the free upper end of the spring falls vertically on the spring so that the spring is compressed by a distance d. The net work done in the process is:-

asked Jul 26, 2018 by pady_1

1 answer

A block B is pushed momentarily along a horizontal surface with an initial velocity v. If $\mu$ is the coefficient of sliding friction between B and the surface, block B will come to rest after time <img src = ""/>:-

asked Jul 26, 2018 by pady_1

1 answer

A particle staring from the origin (0, 0) moves in a straight line in the (x, y) plane. Its coordinates at a later time are($ \sqrt{3},3$) . The path of the parti makes with the x-axis an angle of:-

asked Jul 26, 2018 by pady_1

1 answer

A car moves from X to Y with a uniform speed $v_u$ and returns to Y with a uniform speed $v_d$. The average speed for this round trip is:-

asked Jul 26, 2018 by pady_1

1 answer

A particle moving along x-axis has acceleration $f$, at time $t$, given by $f = f_0 (1 - \frac{t}{T})$, where $f_0$ and $T$ are constants. The particle at t = 0 has zero velocity. In the time interval between $t = 0$ and the instant when $f = 0$, the particle's velocity $(v_x)$ is:

asked Jul 26, 2018 by pady_1

1 answer

Dimensions of resistance in an electrical circuit, in terms of dimension of mass M, of length L, of time T and of current I, would be:-

asked Jul 26, 2018 by pady_1

1 answer

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