List of top Questions asked in JEE Main- 2019

An example of solid sol is :

Aluminium is usually found in $+3$ oxidation stagte. In contarast, thallium exists in $+1$ and $+3$ oxidation states. This is due to :

The correct order of hydration enthalpies of alkali metal ions is -

Which of the following compounds is not aromatic ?

The correct statement regarding the given Ellingham diagram is:

Which is the most suitable reagent for the following transformation ?

Glucose and Galactose are having identical configuration in all the positions except position.

A plano-convex lens (focal length $f_2$, refractive index $\mu_2$, radius of curvature $R$) fits exactly into a plano-concave lens (focal length $f_1$, refractive index $\mu_2$, radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be :

An alpha-particle of mass m suffers 1-dimensional elastic coolision with a nucleus at rest of unknown mass. It is scattered directly backwards losing, $64\%$ of its initial kinetic energy. The mass of the nucleus is :

Voltage rating of a parallel plate capacitor is $500\,V$. Its dielectric can withstand a maximum electric field of $10^6$ V/m. The plate area is $10^{-4} \; m^2$. What is the dielectric constant is the capacitance is $15\, pF$ ? (given $\in_0 = 8.86 \times 10^{-12} C^2 / Nm^2$)

The magnitude of torque on a particle of mass $1\,kg$ is $2.5\, Nm$ about the origin. If the force acting on it is $1\, N$, and the distance of the particle from the origin is $5\,m$, the angle between the force and the position vector is (in radians) :

A load of mass $M\, kg$ is suspended from a steel wire of length $2\, m$ and radius $1.0\, mm$ in Searle's apparatus experiment. The increase in length produced in the wire is $4.0\, mm$. Now the load is fully immersed in a liquid of relative density $2$. The relative density of the material of load is $8$. The new value of increase in length of the steel wire is :

A $10\, m$ long horizontal wire extends from North East to South West. It is falling with a speed of $5.0\,ms^{-1}$, at right angles to the horizontal component of the earth's magnetic field, of $0.3 \times 10^{-4}\,Wb/m^2$. The value of the induced emf in wire is :

A straight rod of length $L$ extends from $x = a$ to $x = L + a$. The gravitational force is exerts on a point mass $'m'$ at $x = 0$, if the mass per unit length of the rod is $A + Bx^2$, is given by:

A particle starts from origin $O$ from rest and moves with a uniform acceleration along the positive $x$-axis. Identify all figures that correctly represent the motion qualitatively. (a = acceleration, v = velocity, x = displacement, t = time)

An electron, moving along the x-axis with an initial energy of $100\, eV$, enters a region of magnetic field $\vec{B} \, = (1.5 \times 10^{-3} T) \hat{k}$ at $S$ (See figure). The field extends between $x = 0$ and $x = 2\, cm$. The electron is detected at the point $Q$ on a screen placed $8\, cm$ away from the point $S$. The distance $d$ between $P$ and $Q$ (on the screen) is : (electron's charge = $1.6 \times 10^{-19}C.$ mass of electron = $9.1 \times 10^{-31}kg)$

Two radioactive materials $A$ and $B$ have decay constants $10 \lambda$ and $\lambda$, respectively. It initially they have the same number of nuclei, then the ratio of the number of nuclei of $A$ to that of $B$ will be $1/e$ after a time :

One plano-convex and one plano-concave lens of same radius of curvature $'R'$ but of different materials are joined side by side as shown in the figure. If the refractive index of the material of $1$ is $\mu_1$ and that of $2$ is $\mu_2$, then the focal length of the combination is :

A vertical closed cylinder is separated into two parts by a frictionless piston of mass $m$ and of negligible thickness. The piston is free to move along the length of the cylinder. The length of the cylinder above the piston is $\ell_1$, and that below the piston is $\ell_2$ , such that $\ell_1$>$\ell_2$. Each part of the cylinder contains $n$ moles of an ideal gas at equal temperature $T$. If the piston is stationary, its mass, $m$, will be given by : (R is universal gas constant and $g$ is the acceleration due to gravity)

Two identical spherical balls of mass $M$ and radius $R$ each are stuck on two ends of a rod of length $2R$ and mass $M$ (see figure). The moment of inertia of the system about the axis passing perpendicularly through the centre of the rod is :

A message signal of frequency $100\, MHz$ and peak voltage $100\, V$ is used to execute amplitude modulation on a carrier wave of frequency $300\, GHz$ and peak voltage $400\, V$. The modulation index and difference between the two side band frequencies are :

A wooden block floating in a bucket of water has $\frac{4}{5}$ of its volume submerged. When certain amount of an oil is poured into the bucket, it is found that the block is just under the oil surface with half of its volume under water and half in oil. The density of oil relative to that of water is :

In the given circuit diagram, the currents, $I_1 = 0.3\,A, I_4 = 0.8\, A$ and $I_5 = 0.4\, A$, are flowing as shown. The currents $I_2,I_3$ and $I_6$,respectively, are :

An organic compound $'A'$ is oxidized with ${Na2O2}$ followed by boiling with ${HNO3}$. The resultant solution is then treated with ammonium molybdate to yield a yellow precipitate. Based on above observation, the element present in the given compound is :

When $100 \,g$ of a liquid A at $100^{\circ}C$ is added to $50\, g$ of a liquid $B$ at temperature $75^{\circ}C$, the temperature of the mixture becomes $90^{\circ}C$. The temperature of the mixture, if $100\, g$ of liquid $A$ at $100^{\circ}C$ is added to $50\, g$ of liquid $B$ at $50^{\circ}C$, will be :