List of practice Questions

A resistor of resistance 30 $\Omega$ and a capacitor of reactance 40 $\Omega$ are connected in series to an ac supply. If the rms current through the resistor is 2 mA, then the wattless current is:

If the average energy density of the electric field of an electromagnetic wave is $U_E$ and the average energy density of the magnetic field of the wave is $U_B$, then:

The energy of a photon of wavelength 2500 is 4.96 eV. When photons of wavelength 3100 incident on a photosensitive material of work function 2.2 eV, the maximum velocity of the emitted photoelectrons is:

In hydrogen atom, if the kinetic energy of an electron in an orbit having angular momentum $2h/\pi$ is E, then the potential energy of the electron in the first orbit of hydrogen atom is:

If decay constant of a radioactive element doubles, then its half-life time becomes:

For the circuit given below, which of the following is correct option?

Two conducting thin concentric shells of radii $r$ and $2r$ are shown. Outer shell carries a charge Q. Inner shell is neutral. The charge that will flow from the inner shell to earth after closing the switch $s$ is: figure [H]

figure

If a wire of length 196 cm carrying a current of 0.98 A is bent in the form of a circular loop of two turns, then the magnetic field at the centre of the loop is approximately:

If a straight infinitely long horizontal wire carries a current of 50 A in east-west direction, then the magnitude of the magnetic field due to the current at a vertical distance of 2 m above the wire is:

If the horizontal component of earth's magnetic field at a place is $2.8 \times 10^{-5}$ T and the magnetic field of the earth at this place is $5.6 \times 10^{-5}$ T, then the inclination at the place is:

The mutual inductance of a pair of adjacent coils is 5 H. If the current in one coil changes from 0 to 12 A in a time of 0.75 s, then the change of flux linkage with the other coil is:

Two waves of wavelengths 50 cm and 51 cm produce 12 beats per second. The velocity of sound is:

A ray of light is incident on a glass plate of refractive index $\sqrt{3}$. If the angle between the refracted ray and reflected ray is $90^\circ$, then the angle of incidence is:

Young's double slit experiment setup is in such a way that, when path difference is $\lambda$, then intensity at a point is I. If the path difference is $\lambda/4$, then intensity at the same point is:

The electric field intensity on the surface of a charged sphere of radius R and volume charge density $\rho$ is:

Three capacitors each of capacitance 10 $\mu$F are to be connected such that the effective capacitance becomes 15 $\mu$F. This can be done by connecting:

Two drops of same radius are falling through air with steady velocity of $5~cms^{-1}$. If the two drops coalesce, the terminal velocity would be:

100 gm of copper is heated to increase its temperature by $21^\circ C$. If the same amount of heat is given to 50 gm of water, then the rise in its temperature is (Specific heat of Cu = $400~J~kg^{-1}K^{-1}$, Water = $4200~J~kg^{-1}K^{-1}$):

Three identical conductors A, B, and C are in contact. Thermal conductivities are k, 2k, and k/2 respectively. A is at $100^\circ C$ and C is at $0^\circ C$. During steady state, the junction temperature between A and B is nearly:

In a thermodynamic process, a gas releases 20 J of heat and 10 J of work is done on the gas. If initial internal energy was 40 J, the final internal energy is:

A thermally insulated vessel contains an ideal gas of molecular weight M and specific heat ratio $\gamma$. If it is moving with speed V and suddenly brought to rest, the temperature increase is:

Two particles of masses $m_1$ and $m_2$ ($m_1 > m_2$) are separated by a distance 'd'. When the positions of the two particles are interchanged, the shift in the centre of mass is:

A uniform rod of mass 20 kg and length 1.6 m is pivoted at its one end and can swing freely in the vertical plane. The angular acceleration of the rod just after the rod is released from rest in the horizontal position is:

The potential energy of a particle of mass 1 kg which is in simple harmonic motion along X-axis is given by $U(x)=4(1-\cos 2x)$. The time period of oscillations is:

Which of the following statements are correct for a particle in simple harmonic motion? I. Its velocity-displacement graph is a parabola. II. Its velocity-time graph is sinusoidal. III. Its velocity-acceleration graph is an ellipse.