WBJEE Physics Test - 12

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A parallel plate capacitor is first charged and then a dielectric slab is introduced between the plates. The quantity that remains unchanged is

Suppose an electron is attracted towards the origin by a force k/r where 'k' is a constant and 'r' is the distance of the electron from the origin . By applying Bohr model to this system , the radius of the n^th orbital of the electron is found to be 'r'_n and the kinetic energy of the electron to be T_n . Then which of the following is true ?

A cylinder of radius r and length a is placed in a uniform in a uniform electric field E parallel to the axis of the cylinder. The total electric flux over the curved surface of cylinder is

If the radius of the earth were to shrink by 1% its mass remaining same, the acceleration due to gravity on the earth's surface would

A rocket with a lift-off mass 3.5 x 10⁴  kg is blasted upwards with an initial acceleration of 10m/s². Then the initial thrust of the blast is

Which of the following relations represent Biot-Savart's law?

A moving coil galvanometer of resistance 100 Ω shows full scale deflection when a current of 100 micro-amperes passes through it. If it is intended to show full scale deflection when a current of 1 milli-ampere passes through it, the value of shunt resistance in ohms to be connected to the galvanometer is

When 2 A current is passed through the coil of a tangent galvanometer, it gives a deflection of 45^o. For 60^o deflection, the current must be

A beaker containing a liquid of density (ρ) moves up with an acceleration (a). The pressure due to liquid at a depth (h) below the surface of the liquid is

A car travelling on a straight track moves with uniform velocity of ν₁ for some time and uniform velocity ν₂ for the next equal time. The average velocity of the car is

An object is projected with a velocity of 20 m/s making an angle of 45^o with horizontal. The equation for the trajectory is h = Ax - Bx² where h is height, x is horizontal distance, A and B are constants. The ratio A : B is (g = 10 ms^-2)

A 1 kg stone at the end of 1 m long string is whirled in a vertical circle at constant speed of 4 m/sec. The tension in the string is 6 N,when the stone is at (g = 10m/sec²)

Consider α -particles, β -particles and γ -rays, each having an energy of 0.5 MeV. In increasing order of penetrating powers, the radiations are

If the displacement of a particle executing S.H.M. is given by y= 0.30 sin (220t+0.64) in metre, then the frequency and maximum velocity of the particle is

Two springs of constants k₁ and k₂, have equal highest velocities, when executing SHM. Then, the ratio of their amplitudes (given their masses are eqaul) will be

'Mirage' is a phenomenon due to

The moment of inertia of a disc of mass M and radius R about an axis, which is tangential to circumference of disc and parallel to its diameter is

A disc is rotating with an angular velocity of ω. If a child sits on it, which of the following is conserved?

In p-n junction, avalanche current flows in circuit when biasing is

The state of the energy gained by valance electrons when the temperature is raised or when electric field is applied is called as

19g of water at 30 ^oC and 5g of ice at − 20 ^oC are mixed together in a calorimeter. What is the final temperature of the mixture ? Given specific heat of ice = 0.5 cal g^-1 oC^-1  and latent heat of fusion of ice = 0.8 cal g^-1 oC^-1

A gas is being compressed adiabatically. The specific heat of the gas during compression is

Hertz is the unit of

If p=7i-2j+3k and q=3i+j+5k, then the modulus of p-2q is

A wavefront is an imaginary surface where

The work done in holding 15 Kg suitcase while waiting for a bus for 15 minutes is

Three block of masses m₁,m₂ and m₃ are connected by massless strings as shown on a frictionless table .They are pulled with a force T₃ = 40 N .If m₁ = 10 kg ,m₂ = 6 kg and m₃ = 4 kg, the tension T₂ will be

Which one of the following has not been expressed in proper units?

Two large metal sheets having surface charge densities σ and − σ are held parallel to each other at a small separation. The electric field at any point in the region between the sheets is

A standing wave on a string is given by y = (4 cm) cos [ π x] sin [50 π t], where x is in metre and t is in seconds. The velocity of the string section at x = 1/3 m at t = 1/5 s, is

A uniform smooth rod placed on a smooth horizontal floor is hit by a particle moving on the floor, at a distance l/4 from one end. Then, the distance travelled by the centre of the rod after the collision when it has completed three revolutions will be [ e ≠ 0, l is the length of the rod]

A coin is placed on a horizontal platform which undergoes horizontal S.H.M. about a mean position O. The coin does not slip on the platform. The force of friction acting on the coin is F.

H⁺, He⁺ and O⁺⁺ all having the same kinetic energy pass through a region in which there is a uniform magnetic field perpendicular to their velocities. The masses of H⁺, He⁺ and O⁺⁺ are 1 amu, 4 and 16 amu respectively. The

Hydrogen gas and oxygen gas have volume 1 cm³ each at N.T.P.

A ray incident on a droplet of water comes out of droplet after two refractions and one reflection. If the deviation suffered by the ray is to be minimum, the condition is

X-rays are produced in an X-ray tube operating at a given accelerating voltage. The wavelength of the continuous X-rays has values from