List of top Questions asked in JEE Main

Which of the following matrices can NOT be obtained from the matrix \(\begin{bmatrix} -1 &2 \\  1 & -1 \end{bmatrix}\) by a single elementary row operation?
Sum of oxidation state (magnitude) and coordination number of cobalt in \(Na[Co(bpy)Cl_4]\) is____ .
(Given : bpy =Sum of oxidation state (magnitude) and coordination number of cobalt)

Let
\(S = \left\{z∈C : z^2+\overline{z} = 0 \right\}\). Then \(∑_{z∈S}(Re(z)+Im(z))\)
is equal to____.

Consider the following sulphur based oxoacids.
\(H_2SO_3,H_2SO_4,H_2S_2O_8 \)and \(H_2S_2O_7\)
Amongst these oxoacids, the number of those with peroxo (O–O) bonds is_____.
As shown in the figure, a potentiometer wire of resistance 20 Ω and length 300 cm is connected with resistance box (R.B.) and a standard cell of emf 4 V. For a resistance ‘R‘ of resistance box introduced into the circuit, the null point for a cell of 20 mV is found to be 60 cm. The value of ‘R ‘ is Ω.
a potentiometer wire of resistance 20 Ω

If the system of equations 
$ x + y + z = 6 $, 
$ 2x + 5y + \alpha z = \beta $, 
$ x + 2y + 3z = 14 $ 
has infinitely many solutions, then $ \alpha + \beta $ is equal to:

In following pairs, the one in which both transition metal ions are colourless is :
Two electric dipoles of dipole moments 1.2 × 10–30 C-m and 2.4 × 10–30 C-m are placed in two different uniform electric fields of strength 5 × 104 NC–1 and 15 × 104 NC–1 respectively. The ratio of maximum torque experienced by the electric dipoles will be 1:x. The value of x is _______
Let
\(\begin{array}{l}f\left(x\right) = min \{\left[x – 1\right], \left[x – 2\right], …., \left[x – 10\right]\}\end{array}\)
where [t] denotes the greatest integer ≤t. Then
\(\begin{array}{l} \displaystyle\int\limits_{0}^{10}f\left(x\right)dx+\displaystyle\int\limits_{0}^{10}\left(f\left(x\right)\right)^2dx+\displaystyle\int\limits_{0}^{10}\left|f\left(x\right)\right|dx\end{array}\)
is equal to ________.
The frequency of echo will be _______ Hz if the train blowing a whistle of frequency 320 Hz is moving with a velocity of 36 km/h towards a hill from which an echo is heard by the train driver. Velocity of sound in air is 330 m/s.
The diameter of an air bubble which was initially 2 mm, rises steadily through a solution of density 1750 kg m–3 at the rate of 0.35 cms–1. The coefficient of viscosity of the solution is _______ poise (in nearest integer). (The density of air is negligible).
A block of mass ‘m’ (as shown in figure) moving with kinetic energy E compresses a spring through a distance 25 cm when its speed is halved. The value of spring constant of used spring will be nE Nm–1 for n = _______.
A block of mass ‘m’
Four identical discs each of mass ‘M’ and diameter ‘a’ are arranged in a small plane as shown in the figure. If the moment of inertia of the system about OO’ is (\(\frac{x}{4}\)) Ma2. Then, the value of x will be _______.
Four identical discs each of mass ‘M’ and diameter ‘a’
Which among the following is the strongest Bronsted base?
Which among the following pairs of the structures will give different products onozonolysis? (Consider the double bonds in the structures are rigid and not delocalized)
The number of stereoisomers formed in a reaction of (±) Ph (C = O) C (OH) (CN) Ph with HCN is_____.
[Where, Ph is – C6H5]
The number of chlorine atoms in bithionol is ______ .
Let the circumcentre of a triangle with vertices A(a, 3), B(b, 5) and C(a, b), ab > 0 be P(1, 1). If the line AP intersects the line BC at the point Q(k1, k2), then k1 + k2 is equal to :
Assuming 1μg of trace radioactive element X with a half life of 30 years is absorbed by a growing tree. The amount of X remaining in the tree after 100 years is ______ × 10–1μg.
[Given : ln 10 = 2.303; log 2 = 0.30]
Correct structure of γ-methylcyclohexane carbaldehyde is
The root mean square speed of smoke particles of mass 5 × 10-17 in their Brownian motion in air at NTP is approximately. [Given k = 1.38 × 10-23 JK-1]
Light enters from air into a given medium at an angle of 45° with interface of the air-medium surface. After refraction, the light ray is deviated through an angle of 15° from its original direction. The refractive index of the medium is
Nearly 10% of the power of a 110 W light bulb is converted to visible radiation. The change in average intensities of visible radiation, at a distance of 1 m from the bulb to a distance of 5 m is a × 10–2 W.m2. The value of ‘a‘ will be _____.



Which among the following represents reagent ‘A’?

Portland cement contains ‘X’ to enhance the setting time. What is ‘X’?