List of top Questions asked in JEE Main- 2021

Given below are two statements : Two photons having equal linear momenta have equal wavelengths. If the wavelength of photon is decreased, then the momentum and energy of a photon will also decrease. In the light of the above statements, choose the correct answer from the options given below.
Two equal capacitors are first connected in series and then in parallel. The ratio of the equivalent capacities in the two cases will be:
Four identical particles of equal masses $1 kg$ made to move along the circumference of a circle of radius $1 m$ under the action of their own mutual gravitational attraction. The speed of each particle will be :
In the given figure, the energy levels of hydrogen atom have been shown along with some transitions marked $A , B , C , D$ and $E$. The transitions $A, B$ and $C$ respectively represent :

In the given circuit the AC source has \(\omega\) = 100 rad s\(^{-1}\). Considering the inductor and capacitor to be ideal, what will be the current I flowing through the circuit ? 

In Millikan's oil drop experiment, what is viscous force acting on an uncharged drop of radius \(2.0 \times 10^{-5}\) m and density \(1.2 \times 10^3\) kgm\(^{-3}\)? Take viscosity of liquid \(= 1.8 \times 10^{-5}\) Nsm\(^{-2}\). (Neglect buoyancy due to air).

Calculate the amount of charge on capacitor of 4 \(\mu\)F. The internal resistance of battery is 1 \(\Omega\): 

 

In the given figure, a battery of emf E is connected across a conductor PQ of length 'l' and different area of cross-sections having radii $r_1$ and $r_2 (r_2<r_1)$. Choose the correct option as one moves from P to Q : 

 

A capacitor of capacitance C=1 $\mu$F is suddenly connected to a battery of 100 volt through a resistor R = 100 $\Omega$. The time taken for the capacitor to be charged to get 50 V is: [Take ln 2 = 0.69] 

 

A coil is placed in a magnetic field \(\vec{B}\) as shown below :
 
A current is induced in the coil because \(\vec{B}\) is : 
 

Given below are two statements:
Statement I: In a diatomic molecule, the rotational energy at a given temperature obeys Maxwell's distribution.
Statement II: In a diatomic molecule, the rotational energy at a given temperature equals the translational kinetic energy for each molecule.
The focal length $f$ is related to the radius of curvature $r$ of the spherical convex mirror by :
In a photoelectric experiment, increasing the intensity of incident light :
A refrigerator consumes an average 35 W power to operate between temperature -10\(^{\circ}\)C to 25\(^{\circ}\)C. If there is no loss of energy then how much average heat per second does it transfer ?
Each side of a box made of metal sheet in cubic shape is 'a' at room temperature 'T', the coefficient of linear expansion of the metal sheet is ' $\alpha^{\prime}$. The metal sheet is heated uniformly, by a small temperature $\Delta T ,$ so that its new temperature is $T +\Delta T$. Calculate the increase in the volume of the metal box.
A current through a wire depends on time as $i = \alpha_0 t + \beta t^2$ where $\alpha_0 = 20 \text{ A/s}$ and $\beta = 8 \text{ As}^{-2}$. Find the charge crossed through a section of the wire in 15 s.
If $Y, K$ and $\eta$ are the values of Young's modulus, bulk modulus and modulus of rigidity of any material respectively. Choose the correct relation for these parameters.
If an emitter current is changed by $4 mA ,$ the collector current changes by $3.5 mA$. The value of $\beta$ will be
An empty LPG cylinder weighs 14.8 kg. When full, it weighs 29.0 kg and shows a pressure of 3.47 atm. In the course of use at ambient temperature, the mass of the cylinder is reduced to 23.0 kg. The final pressure inside of the cylinder is _________ atm. (Nearest integer)

(Assume LPG of be an ideal gas)
The sum of oxidation states of two silver ions in \(\mathrm{[Ag(NH_3)_2][Ag(CN)_2]}\) complex is _____________.
If the conductivity of mercury at \(0^\circ\mathrm{C}\) is \(1.07 \times 10^{6}\ \mathrm{S\,m^{-1}}\) and the resistance of a cell containing mercury is \(0.243\ \Omega\), then the cell constant of the cell is \(x \times 10^{4}\ \mathrm{m^{-1}}\). The value of x is ____________. (Nearest integer)
The spin-only magnetic moment value of \(\mathrm{B_2^+}\) species is _____________ \(\times 10^{-2}\) BM. (Nearest integer)
[Given : \(\sqrt{3} = 1.73\)]
The number of atoms in 8g of sodium is x \(\times\) 10\(^{23}\). The value of x is ____________. (Nearest integer)

[Given : \(N_A = 6.02 \times 10^{23}\ \mathrm{mol^{-1}}\)

Atomic mass of Na = 23.0 u]
A 50 watt bulb emits monochromatic red light of wavelength of 795 nm. The number of photons emitted per second by the bulb is x \(\times\) 10\(^{20}\). The value of x is __________. [Given : h = 6.63 \(\times\) 10\(^{-34}\) Js and c = 3.0 \(\times\) 10\(^8\) ms\(^{-1}\)]
If 80 g of copper sulphate \(\mathrm{CuSO_4 \cdot 5H_2O}\) is dissolved in deionised water to make 5L of solution. The concentration of the copper sulphate solution is x \(\times\) 10\(^{-3}\) mol L\(^{-1}\). The value of x is _____________.

[Atomic masses Cu : 63.54u, S : 32u, O : 16u, H : 1u]