List of top Questions asked in JEE Main

The efficiency of a Carnot’s engine, working between steam point and ice point, will be
In a coil of resistance \(8Ω\), the magnetic flux due to an external magnetic field varies with time as \(Φ=\frac{2}{3}(9−t^2)\).The value of total heat produced in the coil, till the flux becomes zero, will be _ \(J\).
A potentiometer wire of length 300 cm is connected in series with a resistance 780 Ω and a standard cell of emf 4V. A constant current flows through potentiometer wire. The length of the null point for cell of emf20 mV is found to be 60 cm. The resistance of the potentiometer wire is _____ Ω.
A potentiometer wire of length 300 cm is connected in series with a resistance 780 Ω and a standard cell of emf 4V
As per given figures, two springs of spring constants k and 2k are connected to mass m. If the period of oscillation in figure (a)is 3s, then the period of oscillation in figure (b) will be \(\sqrt x\) s. The value of \(x\) is _______
two springs of spring constants k and 2k are connected to mass m.
Time period of a simple pendulum in a stationary lift is ‘T’. If the lift accelerates with \(\frac{g}{6}\) vertically upwards then the time period will be (Where g = acceleration due to gravity)
A thermally insulated vessel contains an ideal gas of molecular mass M and ratio of specific heats 1.4. Vessel is moving with speed ν and is suddenly brought to rest. Assuming no heat is lost to the surrounding and vessel temperature of the gas increases by(R = universal gas constant
Two capacitors having capacitance C1 and C2 respectively are connected as shown in figure. Initially, capacitor C1 is charged to a potential difference V volt by a battery. The battery is then removed and the charged capacitor C1 is now connected to uncharged capacitor C2 by closing the switch S. The amount of charge on the capacitor C2, after equilibrium, is
Two capacitors having capacitance C1 and C2

Given below two statements: One is labelled as Assertion (A) and other is labelled as Reason (R).
Assertion (A) : Non-polar materials do not have any permanent dipole moment.
Reason (R) :When a non-polar material is placed in an electric field, the centre of the positive charge distribution of it’s individual atom or molecule coincides with the centre of the negative charge distribution.
In the light of above statements, choose the most appropriate answer from the options given below.

The magnetic flux through a coil perpendicular to its plane is varying according to the relation \(\varphi = 5t^3 + 4t^2 + 2t - 5\) Weber. If the resistance of the coil is 5 ohm, then the induced current through the coil at t = 2 s will be,
If electric field intensity of a uniform plane electromagnetic wave is given as
\(E = -301.6 \sin(kz - \omega t) \hat{a}_x + 452.4 \sin(k\omega - \omega t) \hat{a}_y \, \frac{V}{m}\)
Then, magnetic intensity ‘H’ of this wave in Am–1 will be :
[Given : Speed of light in vacuum c = 3 × 108ms–1, Permeability of vacuum \(\mu_0 = 4\pi \times 10^{-7}\) NA–2]
In free space, an electromagnetic wave of 3 GHz frequency strikes over the edge of an object of size \(\frac{\lambda}{100}\), where λ is the wavelength of the wave in free space. The phenomenon, which happens there will be
An electron with speed υ and a photon with speed c have the same de-Broglie wavelength. If the kinetic energy and momentum of electron are Ee and pe and that of photon are Eph and pph respectively. Which of the following is correct?
How many alpha and beta particles are emitted when Uranium 92U238 decays to lead 82Pb206
The I–V characteristics of a p-n junction diode in forward bias is shown in the figure. The ratio of dynamic resistance, corresponding to forward bias voltage of 2 V and 4 V respectively, is
I–V characteristics of a p-n junction diode
Choose the correct statement for amplitude modulation :
A ball of mass 0.5 kg is dropped from the height of 10 m. The height, at which the magnitude of velocity becomes equal to the magnitude of acceleration due to gravity, is ___ m.
[Use g = 10 m/s2]

The elastic behavior of material for linear stress and linear strain, is shown in the figure. The energy density for a linear strain of 5×10–4 is ____ kJ/m3. Assume that material is elastic up to the linear strain of 5×10–4
elastic behavior of material for linear stress and linear strain

The elongation of a wire on the surface of the earth is 10–4m. The same wire of same dimensions is elongated by 6 × 10–5m on another planet. The acceleration due to gravity on the planet will be ___ ms–2. (Take acceleration due to gravity on the surface of earth = 10 ms–2)
A 10 Ω, 20 mH coil carrying constant current is connected to a battery of 20 V through a switch. Now after switch is opened current becomes zero in 100 μs. The average e.m.f. induced in the coil is ____V
In a vernier callipers, each cm on the main scale is divided into 20 equal parts. If tenth vernier scale division coincides with nineth main scale division. Then the value of vernier constant will be____ ×10–2 mm
As per the given circuit, the value of current through the battery will be ______ A
value of current through the battery
A 110 V,50 Hz,AC source is connected in the circuit (as shown in figure). 
current through the resistance
The current through the resistance 55Ω, at resonance in the circuit, will be _______ A
An ideal fluid of density 800kgm–3, flows smoothly through a bent pipe (as shown in figure) that tapers in cross-sectional area from a to \(\frac{a}{2}\). The pressure difference between the wide and narrow sections of pipe is 4100 Pa. At wider section, the velocity of fluid is\(\frac{\sqrt{x}}{6}\) ms1 for x=_______. (Given g=10 ms-2)
ideal fluid of density 800kgm–3
A person is standing in an elevator. In which situation, he experiences weight loss?
A block ‘A’ takes 2 s to slide down a frictionless incline of 30° and length ‘l’, kept inside a lift going up with uniform velocity ‘v’. If the incline is changed to 45°, the time taken by the block, to slide down the incline, will be approximately