List of top Questions asked in WBJEE

Three identical thin bar magnets, each of moment M, are placed along three adjacent sides of a regular hexagon as shown in the figure. The resultant magnetic moment of the system is

The vapour pressure of water at 20 °C is 17.5 torr. What will be the no. of moles of water present in one litre of air at 20 °C and 40% relative humidity. (R =0.082 L atm/mol-k)

Which of the following is/are endothermic reaction(s)?

The displacement ($x$) of a particle depends on time ($t$) as $x = \alpha t^2 - \beta t^3$. Then, $\alpha \beta$ is:

Number of particles passing in unit time through unit area perpendicular to the z-axis is given by: 
$N = D \dfrac{(N_2 - N_1)}{(Z_2 - Z_1)}$, 
where $N_2$ and $N_1$ are the number of particles in unit volume at $Z_2$ and $Z_1$. The dimensional formula of $D$ is?

If \( n = 1, 2, 3, \dots \), then \( \cos \alpha \cos 2\alpha \cos 4\alpha \dots \cos^{2n - 1} \alpha \) is equal to: 

The electric potential at a point on the axis of an electric dipole depends upon the distance r (> > a) of the point from centre of the dipole as

The equation of transverse wave is given by $y=5\sin 2\pi (\frac{t}{0.04}-\frac{x}{40}),$ where distance is in $\mathrm{cm}$ and time insecond. The wavelength of wave will be

A body of mass $40\mathrm{kg}$ is resting on a rough horizontal surface and is subjected to a force $P$, which is just enough to start the motion of the body. If ${\mu }_s=5,{\mu }_k=0.4,\mathrm{g}=10\mathrm{m}/{\mathrm{s}}^2$ and the force $P$ is continuously applied on the body, then the acceleration of the body is

In the given system of three blocks, the surfaces are frictionless. The ratio T1/T2 is:

The coercivity of a small magnet where the ferromagnet gets demagnetised is 3 x 10³ Am^–1. The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet gets demagnetised when inside the solenoid, is

At a given place where acceleration due to gravity is ' $8^{\prime }\mathrm{m}/{\mathrm{s}}^2,$ a sphere of lead of density 'd' $\mathrm{kg}/{\mathrm{m}}^3$ is gently released in a column of liquid of density $\rho \mathrm{kg}/{\mathrm{m}}^3$. If $\mathrm{d}>\rho$, the sphere will

A particle moves in xy plane according to the law x = a sin ωt and y = a(1 - cos ωt), where a and w are constant. The particle traces

A parachutist, after bailing out, falls 50 m without friction. When parachute opens, it retards at 2 ms^-2. He reaches the ground with a speed of 3 ms^-1. At what height did he bail out?

A current of i amp flows in the loop having circular arc r metre, subtending an angle  as shown in the figure. The magnetic field at centre O of circle is

Two disks of equal mass but different diameter are connected with an axle system that allows them to roll down an inclined plane together. Both disks start and finish at the same time. Which of the following statements best describes the disks?

In the figure, a horizontal force F is applied such that the block remains stationary. Which of the following statements is false?

In the following common emitter circuit, if β = 100, VCE = 7V, VBE = Negligible and RC = 2 kΩ, then IB is equal to

If the length of the second's hand in a stop-clock is 3 cm, then the angular velocity and linear velocity of the tip is

A copper bar of length 1 m and cross-sectional area 10 × 10^-2 m² has its one end maintained at 100^oC by means of 0.4 kW electric heater. What is the temperature of the other end in steady state, given that the thermal conductivity of copper is 400 W/mK?

The potential energy of a particle varies with distance $x$ from a fixed origin as $\vee =\left(\frac{A\sqrt{x}}{x+B}\right),$ where $A$ and $B$ are constants. The dimensions of AB are

The equation of a wave is $y=5\sin (\frac{t}{0.04}-\frac{x}{4}),$ where $x$ is in $cm$ and $t$ in seconds. The maximum velocity of the particle will be

The value of F so as to keep the smooth wedge stationary, when it is loaded with a block of mass M, which is connected with a light inextensible string, will be

Narrow capillary tubes A and B are of length l and l/2 and of the same radius r. The rate of flow of water through the tube A under a constant pressure head 'P' is 3 cm³/sec. If A and B are connected in series and the same pressure difference 'P' is maintained between the ends of the composite tube, then the rate of flow of water is

A proton is projected with a velocity 10⁷ ms^-1 at right angles to a uniform magnetic field of induction 100 mT. The time (in seconds) taken by the proton to traverse 90^o arc is(Mass of proton = 1.65 × 10^-27 kg and charge of proton = 1.6 × 10^-19 C)