Recent questions in JEEMAIN and NEET

The oxidation state of $Cr$ in $[Cr(NH_3)_4 Cl_2]^+$ is :

asked Nov 5, 2018 by pady_1

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A magnetic needle is kept in a non-uniform magnetic field. It experiences :

asked Nov 5, 2018 by pady_1

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The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp, when not in use ?

asked Nov 5, 2018 by pady_1

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In a potentiometer experiment the balancing with a cell is at length 240 cm. On shunting the cell with a resistance of $ 2 \Omega$, the balancing length becomes 120 cm. The internal resistance of the cell is :

asked Nov 5, 2018 by pady_1

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A charged particle of mass m and charge q travels on a circular path of radius r that is perpendicular to a magnetic field B. The time taken by the particle of complete one revolution is :

asked Nov 5, 2018 by pady_1

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The uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity, then :

asked Nov 5, 2018 by pady_1

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The phase difference between the alternating current and emf is $\pi/2$. Which of the following cannot be the constituent of the circuit ?

asked Nov 5, 2018 by pady_1

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A circuit has a resistance of $12 \Omega$ and an impedance of $15 \Omega$. The power factor of the circuit will be :

asked Nov 5, 2018 by pady_1

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An energy source will supply a constant current into the load, if its internal resistance is :

asked Nov 5, 2018 by pady_1

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The self-inductance of the motor of an electric fan is 10 H. In order to impart maximum power at 50 Hz, it should be connected to a capacitance of :

asked Nov 5, 2018 by pady_1

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A coil of inductance 300 mH and resistance $2 \Omega $ is connected to a source of voltage $2V$. The current reaches half of its steady state value in :

asked Nov 5, 2018 by pady_1

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Two concentric coils each of radius equal to $2 \pi$ cm are placed at right angles to each other. 3A and 4A are the currents flowing in each coil respectively. The magnetic induction in $Wb/m^2$ at the centre of the coils will be : ($\mu_0 = 4 \pi \times 10^{-7} \; Wb/Am$)

asked Nov 5, 2018 by pady_1

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If $I_0$ is the intensity of the principal maximum in the single slit diffraction pattern, then what will be its intensity when the slit width is doubled ?

asked Nov 5, 2018 by pady_1

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An observer moves towards a stationary source of sound, with a velocity one-fifth of the velocity of sound. What is the percentage increase in the apparent frequency ?

asked Nov 5, 2018 by pady_1

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The bob of a simple pendulum is a spherical hollow ball filled with water. A plugged hole near the bottom of the oscillating bob gets suddenly unplugged. During observation, till water is coming out, the time period of oscillation would :

asked Nov 5, 2018 by pady_1

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If a simple harmonic motion is represented by $\frac{d^2x}{dt^2} + \propto x = 0$, its time peroid is :

asked Nov 5, 2018 by pady_1

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When two tuning forks (fork 1 and fork 2) are sounded simultaneously, 4 beats per second are heard. Now, some tape is attached on the prong of the fork 2. When the tuning forks are sounded again, 6 beats per second are heard. If the frequency of fork 1 is 200 Hz, then what was the original frequency of fork 2 ?

asked Nov 5, 2018 by pady_1

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A parallel plate capacitor is made by stacking n equally spaced plates connected alternatively. If the capacitance between any two adjacent plates is C, then the resultant capacitance is :

asked Nov 5, 2018 by pady_1

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Two thin wire rings each having a radius R are placed at a distance d apart with their axes coinciding. The charges on the two rings are $+q$ and $-q$. The potential difference between the centres of the two rings is :

asked Nov 5, 2018 by pady_1

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Two point charges $+8 q$ and $-2q$ are located at $x=0$ and $x=L$ respectively. The location of a point on the $x$-axis at which the net electric field due to these two point charges is zero is :

asked Nov 5, 2018 by pady_1

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A charged ball B hangs from a silk thread S, which makes an angle $\theta$ with a large charged conducting sheet P, as shown in the figure. The surface charge density $\sigma$ of the sheet is proportional to :

asked Nov 5, 2018 by pady_1

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When an unpolarized light of intensity $I_0$ is incident on a polarizing sheet, the intensity of the light which does not get transmitted is:

asked Nov 5, 2018 by pady_1

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Two thin, long, parallel wires, separated by a distance $d$ carry $a$ current of $i$ $A$ in the same direction. They will :

asked Nov 5, 2018 by pady_1

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A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be :

asked Nov 5, 2018 by pady_1

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One conducting U-tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field B is perpendicular to the plane of the figure. If each tube moves towards the other at a constant speed $\nu$, then the emf induced in the circuit in terms of $B, l$ and $\nu$, where $l$ is the width of each tube, will be :

asked Nov 5, 2018 by pady_1

1 answer

A fully charged capacitor has a capacitance $C$. It is discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat capacity $s$ and mass $m$. If the temperature of the block is raised by $\Delta T$, the potential difference $V$ across the capacitance is :

asked Nov 5, 2018 by pady_1

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Two sources of equal emf are connected to an external resistance $R$. The internal resistances of the two sources are $R_1$ and $R_2 (R_2 > R_1)$. If the potential difference across the source having internal resistance $R_2$, is zero, then :

asked Nov 5, 2018 by pady_1

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In the circuit, the galvanometer $G$ shows zero deflection. If the batteries $A$ and $B$ have negligible internal resistance, the value of the resistor $R$ will be:

asked Nov 5, 2018 by pady_1

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Two voltameters, one of copper and another of silver, are joined in parallel. When a total charge $q$ flows through the voltameters, equal amount of metals are deposited. If the electrochemical equivalents of copper and silver are $z_1$ and $z_2$ respectively, the charge which flows through the silver voltameter is :

asked Nov 5, 2018 by pady_1

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A moving coil galvanometer has 150 equal divisions. Its current sensitivity is 10 divisions per milliampere and voltage sensitivity is 2 divisions per millivolt. In order that each division reads 1 V, the resistance in Ohm's needed to be connected in series with the coil will be :

asked Nov 5, 2018 by pady_1

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A nuclear transformation is denoted by $X(n, \alpha) \to ^7_3 Li$. Which of the following is the nucleus of element $X$ ?

asked Nov 5, 2018 by pady_1

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In a full wave rectifier circuit operating from 50 Hz mains frequency, the fundamental frequency in the ripple would be :

asked Nov 5, 2018 by pady_1

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In a common base amplifer, the phase difference between the input signal voltage and output voltage is :

asked Nov 5, 2018 by pady_1

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If the kinetic energy of a free electron doubles, its de-Broglie wavelength changes by the factor :

asked Nov 5, 2018 by pady_1

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The diagram shows the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy ?

asked Nov 5, 2018 by pady_1

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A thin glass (refractive index 1.5) lens has optical power of -5 D in air. Its optical power in a liquid medium with refractive index 1.6 will be :

asked Nov 5, 2018 by pady_1

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Two point white dots are 1 mm apart on a black paper. They are viewed by eye of pupil diameter 3 mm. Approximately, what is the maximum distance at which these dots can be resolved by the eye ? [Take wavelength of light = 500 nm]

asked Nov 5, 2018 by pady_1

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A fish looking up through the water sees the outside world, contained in a circular horizon. If the refractive index of water is $\frac{4}{3}$ and the fish is 12 cm below the water surface, the radius of this circle in cm is :

asked Nov 5, 2018 by pady_1

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Two simple harmonic motions are represented by the equations $y_1 = 0.1 \sin (100 \pi t + \frac{\pi}{3} )$ and $y_2 = 0.1 \cos \pi t$. The phase difference of the velocity of particle 1, with respect to the velocity of particle 2 is :

asked Nov 5, 2018 by pady_1

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A Young's double slit experiment uses a monochromatic source. The shape of the interference fringes formed on a screen is :

asked Nov 5, 2018 by pady_1

1 answer

The function $\sin^2( \omega t)$ represents :

asked Nov 5, 2018 by pady_1

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A system goes from A to B via two process I and II as shown in figure. If $\Delta U_1$ and $\Delta U_2$ are the changes in internal energies in the process I and II respectively, then :

asked Nov 5, 2018 by pady_1

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The figure shows a system of two concentric spheres of radii $r_1$ and $r_2$ and kept at temperature $T_1$ and $T_2$, respectively. The radical rate of flow of heat in a substance between the two concentric spheres, is proportional to :

asked Nov 5, 2018 by pady_1

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The temperature-entropy diagram of a reversible engine cycle is given in the figure. Its efficiency is :

asked Nov 5, 2018 by pady_1

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If radius of the $^{27}_{13} Al$ nucleus is estimated to be 3.6 fermi, then the radius of $^{125}_{52} Te$ nucleus be nearly :

asked Nov 5, 2018 by pady_1

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Starting with a sample of pure $^{66}Cu, 7/8$ of it decays into Zn in 15 min. The corresponding half life is :

asked Nov 5, 2018 by pady_1

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A Photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed $\frac{1}{2}m$ away, the number of electrons emitted by photocahode would :

asked Nov 5, 2018 by pady_1

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The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than 2480 nm, is incident on it. The band gap in (eV) for the semiconductor is :

asked Nov 5, 2018 by pady_1

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The intensity of gamma radiation from a given source is $I$. On passing through 36 mm of lead, it is reduced to $\frac{I}{8}$. The thickness of lead, which will reduce the intensity to$\frac{I}{2}$ will be :

asked Nov 5, 2018 by pady_1

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A gaseous mixture consists of 16 g of helium and 16 g of oxygen. The ratio $\frac{C_p}{C_{\nu}}$ of the mixture is :

asked Nov 5, 2018 by pady_1

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