WBJEE Physics Test - 9

The resistance of a conductor increases with

The current flowing in a step down transformer 220 V to 22 V having impedance 220 Ω is

If electric flux entering and leaving an enclosed surface is φ₁ and φ₂ respectively, the electric charge inside the enclosed surface will be

A charge q is placed at the centre of a cube. The magnitude of electric flux through one of its face will be

If both the mass and radius of the earth decreases by 1%

A machine gun fires a bullet of mass 40 g with a velocity 1200 m−s⁻¹. The man holding it can exert a maximum force of 144 N on the gun. How many bullets can he fire per second at the most?

Proton and α -particle projected perpendicularly in a magnetic field, if both move in a circular path with same speed. Then ratio of their radii is

A charged particle moves in a circular path in a uniform magnetic field. The radius of circular path is R. When kinetic energy of particle is doubled, then new radius will be

Which of the following materials is repelled by an external magnetic field?

A liquid flows through a pipe of non-uniform cross-section. If A₁ and A₂ are the cross-sectional areas of the pipe at two points, the ratio of velocities of the liquid at these points will be

A body moves from rest with a constant acceleration of 5 m/s². Its instantaneous speed (in m/s) at the end of 10 sec is

Two bodies are projected with the same velocity. If one is projected at an angle of 30º and the other at an angle of 60º to the horizontal, the ratio of the maximum heights reached is

When decays to become the particle released is

When the displacement is half of the amplitude, then what fraction of the total energy of a simple harmonic oscillator is kinetic ?

A particle is projected with certain velocity at two different angles of projections with respect to horizontal plane so as to have same range 'R' on a horizontal plane. If 't₁' and 't₂' are the time taken for the two paths, then which one of the following relations is correct?

A spring is stretched by 10 cm when a mass of 1 kg is hanged from it. Now, with the same mass if the spring is pulled and then released, then its time period is 9g=10 m/s²)

In a laboratory four convex lenses L₁, L₂ ,L₃ and L₄ of focal lengths 2, 4, 6 and 8cm, respectively are available. Two of these lenses form a telescope of length 10cm and magnifying power 4. The objective and eye lenses are respectively

A particle performing uniform circular motion has angular momentum L. If its angular frequency is doubled, and its K.E. halved, then the new angular momentum is

The radius of a rotating disc is suddenly reduced to half without any change in its mass. Then its angular velocity will be

The process of adding impurities to the pure semiconductor is called

The dominant contribution to current comes from holes in case of

540 g of ice at 0ºC is mixed with 540 g of water at 80ºC. The final temp. of the mixture in ºC will be

We can not define coefficient of linear or real expansion for a gas, because

The dimensions of stress are equal to

If are any three mutually perpendicular vectors of equal magnitude a then is equal to

In young's double slit experiment, three light, blue, yellow and red are used successively. For which colour, will the fringe width be maximum?

A body of mass 3 kg is under a force which causes a displacement in it given by S = t²/3. Find the work done by the force in first 2 seconds

The speed of sound in oxygen (O₂) at a certain temperature is 460 ms⁻¹. The speed of sound in helium (He) in the same temperature will be (assumed both gases to be ideal)

A stone tied to the end of a sting of 1 m long is whirled in a horizontal circle with a constant speed. If the stone makes 22 revolutions in 44 seconds, what is the magnitude and direction of acceleration of the stone?

Reading shown on two spring balances S₁ and S₂ are 120 kg and 30 kg. respectively, and the lift is accelerating upwards with acceleration 10 m/s². The mass is stationary with respect to lift. Then the mass of the block will be

The pressure-volume graph of an ideal gas cycle consisting of isothermal and adiabatic processes is shown in the figure. The adiabatic process is described by

In the given diagram ,the input is across the terminals A and C and the output is across B and D .Then the output is

A parallel plate capacitor is charged and the charging battery is then disconnected. If the plates of the capacitor are moved farther apart by means of insulating handles

A wave equation which gives the displacement along the y-direction is given by y = 10^-4sin(60t + 2x) where x and y are in metre and t is time in second. This represents a wave

A diverging lens and an object are positioned as shown in the Figure. Which of the rays A, B, C and D could emanate from point Q at the top of the object?

A binary star has stars of masses m and nm (where n is a numerical factor) having separation of their centres as d. If these stars revolve because of gravitational force of each other, then

For the cyclic process shown in the P-V diagram, the area of the bigger triangle is 4A while that of the smaller triangle is A. Which of the following is/are true?