List of top Physics Questions asked in JEE Main

Model a torch battery of length $l$ to be made up of a thin cylindrical bar of radius $'a'$ and a concentric thin cylindrical shell of radius $'b'$ filled in between with an electrolyte of resistivity $\rho$ (see figure). If the battery is connected to a resistance of value $R ,$ the maximum Joule heating in $R$ will take place for :

In a building there are $15$ bulbs of $45\, W, 15$ bulbs of $100\, W$, $15$ small fans of $10\, W$ and $2$ heaters of $1\, kW$. The voltage of electric main is $220\, V$. The minimum fuse capacity (rated value) of the building will be:

A radioactive nucleus decays by two different processes. The half life for the first process is $10 s$ and that for the second is $100 s$. the effective half life of the nucleus is close to:

The activity of a radioactive sample falls from $700\, s^{-1}$ to $500\, s^{-1}$ in 30 minutes. Its half life is close to :

Two gases - argon (atomic radius $0.07\, nm$, atomic weight $40$) and xenon (atomic radius $0.1\, nm$, atomic weight $140$) have the same number density and are at the same temperature. The ratio of their respective mean free times is closest to :

A wire of length $L$ and mass per unit length $6.0 \times 10^{-3} \,kgm^{-1}$ is put under tension of $540\, N$. Two consecutive frequencies that it resonates at are: $420\, Hz$ and $490 \,Hz$. Then $L$ in meters is :

A plane electromagnetic wave is propagating along the direction $\frac{\hat{i}+\hat{i}}{\sqrt{2}},$ with its polarization along the direction $\hat{k}.$ The correct form of the magnetic field of the wave would be (here $B_0$ is an appropriate constant):

A vessel of depth $2\,h$ is half filled with a liquid of refractive index $2\sqrt{2}$ and the upper half with another liquid of refractive index $\sqrt{2}$ The liquids are immiscible. The apparent depth of the inner surface of the bottom of vessel will be :

Planet $A$ has mass $M$ and radius $R$. Planet $B$ has half the mass and half the radius of Planet $A$. If the escape velocities from the Planets $A$ and $B$ are $v_A$ and $v_B$, respectively, then $\frac{v_{A}}{v_{B}}=\frac{n}{4}$. The value of $n$ is :

Consider a sphere of radius $R$ which carries a uniform charge density $\rho$. If a sphere of radius $\frac{R}{2}$ Ls carved out of it, as shown, the ratio $\frac{\left|\overrightarrow{E_{A}}\right|}{\left|\overrightarrow{E_{B}}\right|}$ of magnitude of electric field $\overrightarrow{E_{A}}$ and $\overrightarrow{E}_{B}$ respectively, at points A and B due to the remaining portion is :

A rod of length $L$ has non-uniform linear mass density given by $\rho\left(x\right)=a+b\left(\frac{x}{L}\right)^{2},$ where a and b are constants and $0 \le x \le L.$ The value of $x$ for the centre of mass of the rod is a t :

A bead of mass \(m\) stays at point \(P(a, b)\) on a wire bent in the shape of a parabola \(y=4 c x^{2}\) and rotating with angular speed \(\omega\) (see figure).

The value of \(\omega\) is (neglect friction) :

Consider two solid spheres of radii $R, = 1m, \,R_2 = 2m$ and masses $M_1$ and $M_2$, respectively. The gravitational field due to sphere (1) and (2) are shown. The value of $\frac{m_{1}}{m_{2}}$ is :

A particle is moving unidirectionally on a horizontal plane under the action of a constant power supplying energy source. The displacement (s) - time (t) graph that describes the motion of the particle is (graphs are drawn schematically and are not to scale) :

A 60 HP electric motor lifts an elevator having a maximum total load capacity of 2000 kg. If the frictional force on the elevator is 4000 N, the speed of the elevator at full load is close to : ($1 \,HP = 746 \,W, \,g = 10\, ms^{-2}$ )

Two particles of equal mass m have respective initial velocities $u\hat{i}$ and $u\left(\frac{\hat{i}+\hat{j}}{2}\right).$ They collide completely inelastically. The energy lost in the process is :

A capacitor $C$ is fully charged with voltage $V _{0}$. After disconnecting the voltage source, it is connected in parallel with another uncharged capacitor of capacitance $\frac{ C }{2} .$ The energy loss in the process after the charge is distributed between the two capacitors is :

A capacitor is made of two square plates each of side $'a'$ making a very small angle a between them, as shown in figure. The capacitance will be close to :

A galvanometer of resistance $G$ is converted into a voltmeter of range $0-1 V$ by connecting a resistance $R _{1}$ in series with it. The additional resistance that should be connected in series with $R _{1}$ to increase the range of the voltmeter to $-2 V$ will be :

A particle of charge $q$ and mass $m$ is subjected to an electric field $E = E _{0}\left(1- ax ^{2}\right)$ in the $x$ -direction, where a and $E_{0}$ are constants. Initially the particle was at rest at $x=0$. Other than the initial position the kinetic energy of the particle becomes zero when the distance of the particle from the origin is :

A particle of mass $m$ is fixed to one end of a light spring having force constant $k$ and unstretched length $l$. The other end is fixed. The system is given an angular speed $\omega$ about the fixed end of the spring such that it rotates in a circle in gravity free space. Then the stretch in the spring is :

A thermodynamic cycle $xyzx$ is shown on a $V-T$ diagram. The $P-V$ diagram that best describes this cycle is : (Diagrams are schematic and not to scale)

An amplitude modulated wave is represented by the expression $v _{ m }=5(1+0.6 \cos 6280 t )$ $\sin \left(211 \times 10^{4} t \right)$ volts. The minimum and maximum amplitudes of the amplitude modulated wave are, respectively :

An ideal fluid flows (laminar flow) through a pipe of non-uniform diameter. The maximum and minimum diameters of the pipes are $6.4\, cm$ and $4.8\, cm$, respectively. The ratio of the minimum and the maximum velocities of fluid in this pipe is :

Consider two ideal diatomic gases $A$ and $B$ at some temperature $T$. Molecules of the gas A are rigid , and have an mass $m$. Molecules of the gas $B$ have an additional vibrational mode, and have a mass $\frac{m}{4}.$ The ratio of the specific heats $(C^{A}_{V}$ and $C^{B}_{V})$ of gas $A$ and $B$, respectively is :