List of top Questions asked in JEE Main

The $71^{st}$ electron of an element $X$ with an atomic number of $71$ enters into the orbital :
The effect of lanthanoid contraction in the lanthanoid series of elements by and large means :
A block of mass $m$, lying on a smooth horizontal surface, is attached to a spring (of negligible mass) of spring constant $k$. The other end of the spring is fixed, as shown in the figure. The block is initally at rest in its equilibrium position. If now the block is pulled with a constant force $F$, the maximum speed of the block is :
A paramagnetic substance in the form of a cube with sides $1\, cm$ has a magnetic dipole moment of $20 \times 10^{-6} \; J/T$ when a magnetic intensity of $60 \times 10^3 \; A/m$ is applied. Its magnetic susceptibility is :
The metal that forms nitride by reacting directly with $N_2$ of air, is :
If $'M'$ is the mass of water that rises in a capillary tube of radius $'r'$, then mass of water which will rise in a capillary tube of radius $'2r'$ is :
A homogeneous solid cylindrical roller of radius $R$ and mass $M$ is pulled on a cricket pitch by a horizontal force. Assuming rolling without slipping, angular acceleration of the cylinder is :
Two materials having coefficients of thermal conductivity '3K' and 'K' and thickness 'd' and '3d', respectively, are joined to form a slab as shown in the figure. The temperatures of the outer surfaces are $'\theta_2'$ and $' \theta_1'$ respectively, $(\theta_2 > \theta_1)$. The temperature at the interface is :-
A circular coil having $N$ turns and radius $r$ carries a current $I$. It is held in the $XZ$ plane in a magnetic field $B \hat{i}$ . The torque on the coil due to the magnetic field is :
The coordination numbers of Co and Al in ${ [Co(Cl)(en)2]Cl}$ and ${K3[Al(C2O4)3]}$, respectively, are : (en=ethane-1,2-diamine)
The pH of a 0.02M $NH_4Cl$ solution will be [given $K_b(NH_4OH) = 10^{-5}$ and log2=0.301]
The equation of the plane containing the $\frac{x}{2} = \frac{y}{3} =\frac{z}{4} $ and perpendicular to the plane containing the straight lines $\frac{x}{3} = \frac{y}{4} = \frac{z}{2} $ and $\frac{x}{4} = \frac{y}{2} = \frac{z}{3} $ is :
A solution of sodium sulfate contains $92\, g$ of ${Na^{+}}$ ions per kilogram of water. The molality of ${Na^{+}}$ ions in that solution in ${mol \; kg^{-1}}$ is:
The idea of froth floatation method came from a person $X$ and this method is related to the process $Y$ of ores. $X$ and $Y$, respectively, are:
The number of bridging $CO$ ligand (s) and $Co - Co$ bond (s) in $ {CO_2(CO)_8}$, respectively are :
Two electric dipoles, $A, B$ with respective dipole moments $\vec{d}_A = - 4 \,qa \,\hat{i}$ and $\vec{d}_B = - 2 \,qa\, \hat{i}$ placed on the x-axis with a separation $R$, as shown in the figure The distance from $A$ at which both of them produce the same potential is :
A steel wire having a radius of $2.0\, mm$, carrying a load of $4 \,kg$, is hanging from a ceiling. Given that $g = 3.1 \; \pi \; ms^{-2}$, what will be the tensile stress that would be developed in the wire ?
Consider the given plots for a reaction obeying Arrhenius equation $(0^{\circ}C < T < 300^{\circ}C)$ : ($k$ and $E_a$ are rate constant and activation energy, respectively) Choose the correct option :
The metal used for making $X$-ray tube window is :
Which of the following is a condensation polymer?
A particle is executing simple harmonic motion (SHM) of amplitude A, along the $x$-axis, about $x = 0$. When its potential Energy (PE) equals kinetic energy (KE), the position of the particle will be :
Which is wrong with respect to our responsibility as a human being to protect our environment ?
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 = $9.1 \times 10^{-31}kg)$
Poly-$\beta$-hydroxybutyrate-co-$\beta$ hydroxyvalerate (PHBV) is a copolymer of___.
A magnet of total magnetic moment $10^{-2} \hat{i} \; A-m^2$ is placed in a time varying magnetic field, $B \hat{i} (\cos t\omega t)$ where $B = 1 $Tesla and $\omega = 0.125 \; rad/s$. The work done for reversing the direction of the magnetic moment at $t = 1$ second, is :