List of top Questions asked in JEE Main- 2021

What will be the magnitude of electric field at point O as shown in the figure? Each side of the figure is $l$ and mutually perpendicular. 

 

The maximum amplitude for an amplitude modulated wave is found to be 12 V while the minimum amplitude is found to be 3 V. The modulation index is 0.6x where x is ________ .

For the circuit shown, the value of current at time t=3.2 s will be ________ A. 

 

In the given figure the magnetic flux through the loop increases according to the relation $\phi_B(t) = 10t^2 + 20t$, where $\phi_B$ is in milliwebers and t is in seconds. The magnitude of current through R=2.0 $\Omega$ resistor at t=5 s is ________ mA. 

 

The K$_\alpha$ X-ray of molybdenum has wavelength 0.071 nm. If the energy of a molybdenum atom with a K electron knocked out is 27.5 keV, the energy of this atom when an L electron is knocked out will be ________ keV. (Round off to the nearest integer)
[ h = $4.14 \times 10^{-15}$ eVs, c = $3 \times 10^8$ ms$^{-1}$ ]
The water is filled upto height of 12 m in a tank having vertical sidewalls. A hole is made in one of the walls at a depth 'h' below the water level. The value of 'h' for which the emerging stream of water strikes the ground at the maximum range is ________ m.

In the given figure, two wheels P and Q are connected by a belt B. The radius of P is three times as that of Q. In case of same rotational kinetic energy, the ratio of rotational inertias $(\frac{I_1}{I_2})$ will be x : 1. The value of x will be ________ . 

 

A small block slides down from the top of hemisphere of radius R=3 m as shown in the figure. The height 'h' at which the block will lose contact with the surface of the sphere is ________ m. (Assume there is no friction between the block and the hemisphere) 

 

A swimmer wants to cross a river from point A to point B. Line AB makes an angle of 30$^\circ$ with the flow of river. Magnitude of velocity of the swimmer is same as that of the river. The angle $\theta$ with the line AB should be ________ $^\circ$, so that the swimmer reaches point B. 

 

A particle executes simple harmonic motion represented by displacement function as x(t) = A sin($\omega$t+$\phi$). If the position and velocity of the particle at t = 0 s are 2 cm and 2$\omega$ cm s$^{-1}$ respectively, then its amplitude is $x\sqrt{2}$ cm where the value of x is ________.
The difference in the number of waves when yellow light propagates through air and vacuum columns of the same thickness is one. The thickness of the air column is ________ mm.
[Refractive index of air = 1.0003, wavelength of yellow light in vacuum = 6000 Å]
Select the correct statements.
(A) Crystalline solids have long range order.
(B) Crystalline solids are isotropic.
(C) Amorphous solids are sometimes called pseudo solids.
(D) Amorphous solids soften over a range of temperatures.
(E) Amorphous solids have a definite heat of fusion.
Choose the most appropriate answer from the options given below :
If the Thompson model of the atom was correct, then the result of Rutherford's gold foil experiment would have been :
Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : SO$_2$(g) is adsorbed to a larger extent than H$_2$(g) on activated charcoal.
Reason R : SO$_2$(g) has a higher critical temperature than H$_2$(g).
In the light of the above statements, choose the most appropriate answer from the options given below.
The CORRECT order of first ionisation enthalpy is :
The number of neutrons and electrons, respectively, present in the radioactive isotope of hydrogen is :
The addition of silica during the extraction of copper from its sulphide ore

Match List - I with List - II : 

Choose the correct answer from the options given below : 
 

Number of Cl=O bonds in chlorous acid, chloric acid and perchloric acid respectively are :
To an aqueous solution containing ions such as Al$^{3+}$, Zn$^{2+}$, Ca$^{2+}$, Fe$^{3+}$, Ni$^{2+}$, Ba$^{2+}$ and Cu$^{2+}$ was added conc. HCl, followed by H$_2$S.
The total number of cations precipitated during this reaction is/are :
Given below are two statements :
Statement I : [Mn(CN)$_6$]$^{3-}$, [Fe(CN)$_6$]$^{3-}$ and [Co(C$_2$O$_4$)$_3$]$^{3-}$ are d$^2$sp$^3$ hybridised.
Statement II : [MnCl$_6$]$^{3-}$ and [FeF$_6$]$^{3-}$ are paramagnetic and have 4 and 5 unpaired electrons, respectively.
Choose the correct option.

Match List - I with List - II : 

Choose the correct answer from the options given below : 
 

Which one of the following set of elements can be detected using sodium fusion extract ?
Given below are two statements :
Statement I : Hyperconjugation is a permanent effect.
Statement II : Hyperconjugation in ethyl cation \( (\mathrm{CH_3-CH_2^+}) \) involves the overlapping of \( \mathrm{C_{sp^2}-H_{1s}} \) bond with empty \( 2p \) orbital of the other carbon.
Choose the correct option :

Consider the above reaction, the major product "P" formed is :