List of top Questions asked in JEE Main

Surface of certain metal is first illuminated with light of wavelength $\lambda_1 =350 \; nm$ and then, by light of wavelength $\lambda_2=54\, \; nm$. It is found that the maximum speed of the photo electrons in the two cases differ by a factor of $2$. The work function of the metal (in eV) is close to : (Energjr of photon = $\frac{1240}{\lambda (in \; nm)} eV$)

Three particles of masses $50\, g, 100\, g$ and $150\, g$ are placed at the vertices of an equilateral triangle of side $1\, m$ (as shown in the figure). The $(x, y)$ coordinates of the centre of mass will be :

Two masses $m$ and $\frac{m}{2}$ are connected at the two ends of a massless rigid rod of length $l$. The rod is suspended by a thin wire of torsional constant $k$ at the centre of mass of the rod-mass system(see figure). Because of torsional constant $k$, the restoring torque is $\tau =k\theta$ for angular displacement $\theta$. If the rod is rota ted by $\theta_0$ and released, the tension in it when it passes through its mean position will be:

For a uniformly charged ring of radius $R$, the electric field on its axis has the largest magnitude at a distance $h$ from its centre. Then value of $h$ is :

Charge is distributed within a sphere of radius $R$ with a volume charge density $p (r) = \frac{A}{r^2} e^{-2r/a}$ where $A$ and $a$ are constants. If $Q$ is the total charge of this charge distribution, the radius $R$ is :

A copper wire is stretched to make it $0.5 \%$ longer. The percentage change in its electrical resistance if its volume remains unchanged is:

A potentiometer wire $AB$ having length $L$ and resistance $12\, r$ is joined to a cell $D$ of emf $\varepsilon$ and internal resistance $r$. A cell $C$ having $emf \, \varepsilon /2$ and internal resistance $3r$ is connected. The length $AJ$ at which the galvanometer as shown in fig. shows no deflection is :

A resistance is shown in the figure. Its value and tolerance are given respectively by :

${5.1g \; NH_4SH }$ is introduced in $3.0\, L$ evacuated flask at ${327^{\circ}C}$. 30% of the solid ${NH4SH}$ decomposed to ${NH_3}$ and ${H2S}$ as gases. The Kp of the reaction at ${327^{\circ}C}$ is ${(R = 0.082 \; L \; atm \; mol^{-1} K^{-1}}}$, Molar mass of ${S = 32 \; g \; mol/^{01}}$, molar mass of ${N = 14g \, mol^{-1}}$)

The actual value of resistance $R$, shown in the figure is $30 \Omega $. This is measured in an experiment as shown using the standard formula $R = \frac{V}{I}$ , where $V$ and $I$ are the readings of the voltmeter and ammeter, respectively. If the measured value of $R$ is $5\%$ less, then the internal resistance of the voltmeter is :

A rigid square loop of side 'a' and carrying current I$_2$ is lying on a horizontal surface near a long current I$_1$ carrying wire in the same plane as shown in figure. The net force on the loop due to wire will be :

Homoleptic octahedral complexes of a metal ion '${M^{3+} }$' with three monodentate ligands and $L_1, L_2, L_3$ absorb wavelengths in the region of green, blue and red respectively. The increasing order of the ligand strength is :

The peptide that gives positive ceric ammonium nitrate and carbylamine tests is :

The Mond process is used for the

Determine the charge on the capacitor in the following circuit :

In the circuit shown, the switch $S_1$ is closed at time $t = 0$ and the switch $S_2$ is kept open. At some later time $(t_0)$, the switch $S_1$ is opened and $S_2$ is closed. The behavious of the current $I$ as a function of time $'t'$ is given by :

The aerosol is a kind of colloid in which :

The compound used in the treatment of lead poisoning is :

The concentration of dissolved oxygen $(DO)$ in cold water can go upto :

The correct statements among (a) to (b) are: (a) saline hydrides produce $H_2$ gas when reacted with ${H2O}$. (b) reaction of $LiAH_4$ with $BF_3$ leads to $B_2H_6$. (c) $PH_3$ and $CH_4$ are electron - rich and electronprecise hydrides, respectively. (d) HF and $CH_4$ are called as molecular hydrides.

The decreasing order of electrical conductivity of the following aqueous solutions is : 0.1 M Formic acid (A), 0.1 M Acetic acid (B) 0.1 M Benzoic acid (C)

Two identical breakers A and B contain equal volumes of two different liquids at $60^{\circ}C$ each and left to cool down. Liquid in A has density of $8 \times 10^2 \; kg/m^3$ and sp ecific heat o f 2000 J $kg^{-1} \; K^{-1}$ while liquid in B has density o f 103 kg m-3 and sp ecific heat o f 4000 J $kg^{-1} K^{-1}$. Which of the following best describes their temperature versus time graph schematically? (assume the emissivity of both the beakers to be the same)

Molal depression constant for a solvent is $4.0\, kg\, mol^{-1}$. The depression in the freezing point of the solvent for $0.03\, mol\, kg^{-1}$ solution of $ {K2SO4}$ is : (Assume complete dissociation of the electrolyte)

Peptization is a :

The plane which bisects the line segment joining the points (-3,-3,4) and (3,7,6) at right angles, passes through which one of the following points ?