WBJEE Previous Year - 2012 - JEE MCQ

If the velocity of light in vacuum is 3 x 10⁸ ms^–1, the time taken (in nanosecond) to travel through a glass of thickness 10 cm and refractive index 1.5 is

A charge +q is placed at the orgin O of X – Y axes as shown in the figure. The work done in taking a charge Q from A to B along the straight line AB is

What current will flow through 2 k resistor in the circuit shown in the figure?

In a region, the intensity of an electric field is given by  in NC^–1. The electric flux through a surface  in the region is

A train approaching a railway platform with a speed of 20 ms^–1 starts blowing the whistle. Speed of sound in air is 340 ms^–1. If the frequency of the emitted sound from the whistle is 640 Hz, the frequency of sound to a person standing on the platform will appear to be

A straight wire of length 2 m carries a current of 10 A. If this wire is placed in a uniform magnetic field of 0.15 T making an angle of 45^o with the magnetic field, the applied force on the wire will be

What is the phase difference between two simple harmonic motions represented by    and x₂ = A cos (ωt)?

Heat is produced at a rate given by H in a resistor when it is connected across a supply of voltage V. If now the resistance of the resistor is doubled and the supply voltage is made V/3 then the rate of production of heat in the resistor will be

Two elements A and B with atomic numbers Z_A and Z_B are used to produce characteristic x–rays with frequencies A and B respectively. If Z_A : Z_B= 1 : 2, then v_A : v_B will be

The de Broglie wavelength of an electron moving with a velocity c/2 (c = velocity of light in vacuum) is equal to the wavelength of a photon. The ratio of the kinetic energies of electron and photon is

Two infinite parallel metal planes, contain electric charges with charge densities + and – respectively and they are separated by a small distance in air. If the permittivity of air is 0 then the magnitude of the field between the two planes with its direction will be

A box of mass 2 kg is placed on the roof of a car. The box would remain stationary until the car attains a maximum acceleration. Coefficient of static friction between the box and the roof of the car is 0.2 and g = 10 ms^–2.This maximum acceleration of the car, for the box to remain stationary, is

The dimension of angular momentum is

 have scalar magnitudes of 5, 4 , 3 units respectivley then the angle between A and C is

A particle is travelling along a straight line OX. The distance x (in meters) of the particle from O at a time t is given by x = 37 + 27 t – t³ where t is time in seconds. The distance of the particle from O when it comes to rest is

A particle is projected from the ground with kinetic energy E at an angle of 60⁰ with the horizontal. Its kinetic energy at the highest point of its motion will be

A bullet on penetrating 30 cm into its target loses its velocity by 50%. What additional distance will it penetrate into the target before it comes to rest?

When a spring is stretched by 10 cm, the potential energy stored is E. When the spring is stretched by 10 cm more, the potential energy stored in the spring becomes

Average distance of the earth from the Sun is L_1. If one year of the Earth = D days, one year of another planet whose average distance from the Sun is L₂ will be

A spherical ball A of mass 4 kg, moving along a straight line strikes another spherical ball B of mass 1 kg at rest.
After the collision, A and B move with velocities v₁ ms^–1 and v₂ ms^–1 respectively making angles of 30^o and 60^o with respect to the original direction of motion of A. The ratio v₁/v₂ will be

The decimal number equivalent ot a binary number 1011001 is

The frequency of the first overtone of a closed pipe of length l₁ is equal to that of the first overtone of an open pipe of length l₂. The ratio of their lenghts (l₁ : l₂) is

The I – V characteristics of a metal wire at two different temperatures (T₁ and T₂) are given in the adjoining figure. Here, we can conclude that

In a slide calipers, (m + 1) number of vernier divisions is equal to m number of smallest main scale divisions. If d unit is the magnitude of the smallest main scale division, then the magnitude of the vernier constant is

From the top of a tower, 80 m high from the ground, a stone is thrown in the horizontal direction with a velocity of 8 ms^–1. The stone reaches the ground after a time ‘t’ and falls at a distance of ‘d’ from the foot of the tower. Assuming g = 10 ms^–2, the time t and distance d are given respectively by

A Wheatstone bridge has the resistances 10 Ω , 10 Ω , 10Ω and 30 Ω in its four arms. What resistance joined in parallel to the 30 resistance will bring it to the balanced condition?

An electric bulb marked as 50 W–200 V is connected across a 100 V supply. The present power of the bulb is