Recent questions in JEEMAIN PAST PAPERS

A conducting square loop of side $L$ and resistance $R$ moves in its plane with a uniform velocity $v$ perpenticular to one of its sides. A magnetic induction $B$ constant in time and space, pointing perpendicular and into the plane at the loop exists everywhere with half the loop outside the field, aas shown in figure. The induced emf is :

asked Dec 11, 2018 by pady_1

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Formation of covalent bonds in compounds exhibits :

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Sodium and copper have work functions $2.3 eV$ and $4.5 eV$ respectively. Then the ratio of the wavelengths is nearest to :

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At a specific instant emission of radioactive compound is deflected in a magnetic field. The compound can emit : (i) electrons (ii) protons (iii) $He^{2+}$ (iv) neutrons The emission at the instant can be :

asked Dec 11, 2018 by pady_1

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Wires 1 and 2 carrying currents $i_1$ and $i_2$ respectively are inclined at an angle $\theta$ to each other. What is the force on a small element $dl$ of wire 2 at a distance $r$ from wire 1 (as shown in figure) due to the magnetic field of wire 1 ?

asked Dec 11, 2018 by pady_1

1 answer

A particle of mass $m$ mooves along line PC with velocity $v$ as shown. What is the angular momentum of the particle about $O$ ?

asked Dec 11, 2018 by pady_1

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One end of massless rope, which passes over a massless and frictionless pulley $P$ is tied to a hook $C$ while the other end is free. Maximum tension that the rope can bear is 360 N. With what value of maximum safe acceleration (in $ms^{-2}$) can a man of 60 kg climb on the rope ?

asked Dec 11, 2018 by pady_1

1 answer

Three identical blocks of masses $m = 2\; kg$ are drawn by a force $F=10.2 N$ with an acceleration of $0.6\;ms^{-2}$ on a frictionless surface, then what is the tension (in $N$) in the string between the blocks B and C ?

asked Dec 11, 2018 by pady_1

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Two spheres of the same material have radii $1m$ and $4m$ and temperatures $4000 K$ and $2000 K$ respectively. The ratio of the energy radiated per second by the first sphere to that by the second is :

asked Dec 11, 2018 by pady_1

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A light string passing over a smooth light pulley connects two blocks of masses $m_1$ and $m_2$ (vertically). If the acceleration of the system is $g/8$, then the ratio of the masses is :

asked Dec 11, 2018 by pady_1

1 answer

Capacitance (in F) of a spherical conductor having radius 1 m, is :

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If a charge $q$ is placed at the centre of the line joining two equal charges $Q$ such that the system is in equilibrium them the value of $q$ is :

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1 mole of a gas with $\gamma = 7/5$ is mixed with 1 mole of a gas with $\gamma = 5/3$, then the value of $\gamma$ for the resulting mixture is :

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Speeds of two identical cars are $u$ and $4u$ at a specific instant. The ratio of the respective distances at which the two cars are stopped from that instant is :

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Two forces are such that the sum of their magnitudes is 18 N and their resultant which has magnitude 12 N, is perpendicular to the smaller force. Then the magnitudes of the forces are :

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When forces $F_1, \; F_2, \; F_3$ are acting on particle of mass $m$ such that $F_2$ and $F_3$ are mutually perpendicular, then the particle remains stationary . If the force $F_1$ is now removed then the acceleration of the particle is :

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Moment of inertia of a circular wire of mass M and radius R about its diameter is :

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Even Carnot engine cannot give 100% efficiency because we cannot :

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In a transformer, number of turns in the primary are 140 and that in the secondary are 280. If current in primary is 4 A, then that in the secondary is :

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A solid sphere, a hollow sphere and a ring are released from top of an inclined plane (frictionless) so that they slide down the plane. Then maximum acceleration down the plane is for (no rolling ) :

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The time period of a charged particle undergoing a circulr motion in a unifrom magnetic field is independent of its :

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At what temperature is the rms velocity of a hydrogen molecule equal to that of an oxygen molecule at $47^{\circ}C$ ?

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The mass of a product liberated on anode in an electrochemical cell depends on :

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A lift is moving down with acceleration $a$. A man in the lift drops a ball inside the lift. The acceleration of the ball as observed by the man in the lift and a man standing stationary on the ground are respectively :

asked Dec 11, 2018 by pady_1

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A child swinging on a swing in sitting position, stands up, then the time period of the swing will :

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A spring of force constant 800 N/m has an extension of 5 cm. The work done in extending it from 5 cm to 15 cm is :

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A cylinder of height 20 m is completely filled with water. The velocity of efflux of water (in $ms^{-1}$) through a small hole on the side wall of the cylinder near its bottom, is :

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The minimum velocity (in $ms^{-1})$ with which a car driver must traverse a flat curve of radius 150 m and coefficient of friction 0.6 to avoid skidding is :

asked Dec 11, 2018 by pady_1

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Initial angular velocity of a circular disc of mass $M$ is $\omega_1$. Then two small spheres of mass $m$ are attached gently to two diametrically opposite point on the edge of the disc. What is the final angular velocity of the disc ?

asked Dec 11, 2018 by pady_1

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In a simple harmonic oscillator, at the mean position :

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The part of a transistor which is most heavily doped to produce large number of majority carries is :

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The energy band gap is maximum in :

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If mass-energy equivalence is taken into account, when water is cooled to form ice, the mass of water should :

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When temperature increases, the frequency of a tuning fork :

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Cooking gas containers are kept in a lorry moving with uniform speed. The temperature of the gas molecules inside will :

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The kinetic energy needed to project a body of mass $m$ from the earth's surface (radius R) to infinity is :

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An astronomical telescope has a large aperture to `:

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The power factor of an AC circuit having resistance $R$ and inductance $L$ (connected in series) and an angular velocity $\omega$ is :

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Length of a string tied to two rigid supports is $40 \; cm$. Maximum length (wavelength in cm) of a stationary wave produced on it, is :

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Which statement is incorrect ?

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Which of the following is more close to a black body ?

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If there are $n$ capacitors in parallel connected to $V$ volt source, then the energy stored is equal to :

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By increasing the temperature, the specific resistance of a conductor and a semiconductor :

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If $N_0$ is the original mass of the substance of half-life period $t_{1/2} = 5\; years$, then the amount of substance left after 15 years is

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Infrared radiations are detected by :

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If $\theta_i$ is the inversion temperature, $\theta_n$ is the neutral temperature, $\theta_c$ is the temperature of the cold junction then :

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Identify the pair whose dimension are equal :

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1 answer

Which of the following are not electromagnetic waves ?

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The escape velocity of a body depends upon mass as :

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Which of the following is used in optical fibres ?

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