List of top Questions asked in JEE Main- 2020

Two charged thin infinite plane sheets of uniform surface charge density \(\sigma_+\) and \(\sigma_-\), where \(|\sigma_+| \gt |\sigma_-|\), intersect at right angle. Which of the following best represents the electric field lines for this system :

A wire A, bent in the shape of an arc of a circle, carrying a current of 2 A and having radius 2 cm and another wire B, also bent in the shape of arc of a circle, carrying a current of 3 A and having radius of 4 cm, are placed as shown in the figure. The ratio of the magnetic fields due to the wires A and B at the common centre O is :

A small bar magnet is moved through a coil at constant speed from one end to the other. Which of the following series of observations will be seen on the galvanometer G attached across the coil ?

Three positions shown describe : (a) the magnet's entry (b) magnet is completely inside and (c) magnet's exit.

A Tennis ball is released from a height \(h\) and after freely falling on a wooden floor it rebounds and reaches height \(\frac{h}{2}\). The velocity versus height of the ball during its motion may be represented graphically by :
(graph are drawn schematically and on not to scale)

Blocks of masses \(m\), \(2m\), \(4m\) and \(8m\) are arranged in a line on a frictionless floor. Another block of mass \(m\), moving with speed \(v\) along the same line (see figure) collides with mass \(m\) in perfectly inelastic manner. All the subsequent collisions are also perfectly inelastic. By the time the last block of mass \(8m\) starts moving the total energy loss is \(p\%\) of the original energy. Value of 'p' is close to :

ABC is a plane lamina of the shape of an equilateral triangle. D, E are mid points of AB, AC and G is the centroid of the lamina. Moment of inertia of the lamina about an axis passing through G and perpendicular to the plane ABC is \(I_0\). If part ADE is removed, the moment of inertia of the remaining part about the same axis is \(\frac{NI_0}{16}\) where N is an integer. Value of N is ____.

\(E^{\circ}_{\mathrm{Cu^{2+}|Cu}} = +0.34\ \mathrm{V}\)
\(E^{\circ}_{\mathrm{Zn^{2+}|Zn}} = -0.76\ \mathrm{V}\)
Identify the incorrect statement from the options below for the above cell :

For the equilibrium \(\mathrm{A} \rightleftharpoons \mathrm{B}\), the variation of the rate of the forward (a) and reverse (b) reaction with time is given by :

[P] on treatment with \(\mathrm{Br_2/FeBr_3}\) in \(\mathrm{CCl_4}\) produced a single isomer \(\mathrm{C_8H_7O_2Br}\) while heating [P] with sodalime gave toluene. The compound [P] is :

The decreasing order of reactivity of the following organic molecules towards \(\mathrm{AgNO_3}\) solution is :

A perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a paramagnetic substance. The whole system is placed in a uniform magnetic field \(\vec{B}\). Then the field inside the paramagnetic substance is :

An organic compound (A) (molecular formula \(\mathrm{C_6H_{12}O_2}\)) was hydrolysed with dil. \(\mathrm{H_2SO_4}\) to give a carboxylic acid (B) and an alcohol (C). 'C' gives white turbidity immediately when treated with anhydrous \(\mathrm{ZnCl_2}\) and conc. HCl. The organic compound (A) is :

The intermolecular potential energy for the molecules A, B, C and D given below suggests that :

When neopentyl alcohol is heated with an acid, it slowly converted into an 85 : 15 mixture of alkenes A and B, respectively. What are these alkenes ?

The IUPAC name of the following compound is :

The number of chiral centres present in [B] is ________.

(Reaction scheme as drawn: 3-methylcyclohexyl-CH(CH₃)-C\(\equiv\)N; (i) C₂H₅MgBr, (ii) H₃O⁺ gives [A]; the same nitrile with (i) CH₃MgBr, (ii) H₂O gives [B].)

A uniform rod of length '\(l\)' is pivoted at one of its ends on a vertical shaft of negligible radius. When the shaft rotates at angular speed \(\omega\) the rod makes an angle \(\theta\) with it (see figure). To find \(\theta\) equate the rate of change of angular momentum (direction going into the paper)
\(\dfrac{ml^2}{12}\omega^2\sin\theta\cos\theta\)
about the centre of mass (CM) to the torque provided by the horizontal and vertical forces \(F_H\) and \(F_V\) about the CM. The value of \(\theta\) is then such that :

An massless equilateral triangle EFG of side 'a' (As shown in figure) has three particles of mass m situated at its vertices. The moment of inertia of the system about the line EX perpendicular to EG in the plane of EFG is \(\dfrac{N}{20}ma^2\) where N is an integer. The value of N is _____.

Consider the following molecules and statements related to them :

(a) (B) is more likely to be crystalline than (A)
(b) (B) has higher boiling point than (A)
(c) (B) dissolves more readily than (A) in water
Identify the correct option from below :

The major product in the following reaction is :

The decreasing order of reactivity of the following compounds towards nucleophilic substitution (S_N2) is :

Three isomers A, B and C (mol. formula \(\mathrm{C_8H_{11}N}\)) give the following results :

R has lower boiling point than S
A, B and C, respectively are :

Consider the following reaction :

The product 'P' gives positive ceric ammonium nitrate test. This is because of the presence of which of these -OH group(s)?

100 mL of 0.1 M HCl is taken in a beaker and to it 100 mL of 0.1 M NaOH is added in steps of 2 mL and the pH is continuously measured. Which of the following graphs correctly depicts the change in pH?

The compound A in the following reaction is :