List of top Questions asked in CBSE CLASS XII- 2024

An infinite straight conductor is kept along \( X'X \) axis and carries a current \( I \). A charge \( q \) at point \( P(0, r) \) starts moving with velocity \( \vec{v} = v_0 \, \hat{j} \) as shown in figure. Find the direction and magnitude of force initially experienced by the charge. 

In the given network, calculate: 
(i) Effective resistance between points A and M, and 
(ii) Power supplied by the battery. 

Two conducting spherical shells A and B of radii \( R \) and \( 2R \) are kept far apart and charged to the same charge density \( \sigma \). They are connected by a wire. Obtain an expression for the final potential of shell A.

Find the temperature at which the resistance of a conductor increases by 25% of its value at \( 27^\circ \text{C} \). The temperature coefficient of resistance of the conductor is \( 2.0 \times 10^{-4} \, \text{C}^{-1} \).

The r.m.s. value of a current given by \( i = (i_1 \cos \omega t + i_2 \sin \omega t) \) is:

An infinitely long straight wire having a charge density \( \lambda \) is kept along the y-axis in the x-y plane. The Coulomb force on a point charge \( q \) at a point \( P(x, 0) \) will be:

An electric dipole of dipole moment \( \vec{p} \) is kept in a uniform electric field \( \vec{E} \). The amount of work done to rotate it from the position of stable equilibrium to that of unstable equilibrium will be:

What is meant by displacement current? How is this current different from the conduction current? A capacitor is being charged by a source of emf. Justify the continuity of current in the circuit.

A thin spherical conducting shell of radius \( R \) has a charge \( q \). A point charge \( Q \) is placed at the center of the shell. Find:
(i) The charge density on the outer surface of the shell.
(ii) The potential at a distance \( R/2 \) from the center of the shell.

Two wires A and B of different metals have their lengths in the ratio 1:2 and their radii in the ratio 2:1 respectively. The I-V graphs for them are shown in the figure. Find the ratio of their:
(i) Resistances \( \frac{R_A}{R_B} \)
(ii) Resistivities \( \frac{\rho_A}{\rho_B} \)

In normal adjustment, for a refracting telescope, the distance between the objective and the eyepiece lens is 1.00 m. If the magnifying power of the telescope is 19, find the focal length of the objective and the eyepiece lens.

An AC source \( V = 282 \sin(100t) \) volt is connected across a \( 1 \mu F \) capacitor. The RMS value of current in the circuit will be (Take \( \sqrt{2} = 1.41 \)):

A particle of mass \( m \) and charge \( q \) is moving with velocity \( \mathbf{v} = v_x \hat{i} + v_y \hat{j} \). If it is subjected to a magnetic field \( \mathbf{B} = B_0 \hat{i} \), it will move in a:

The Coulomb force (\( F \)) versus \( \frac{1}{r^2} \) graphs for two pairs of point charges (\( q_1 \) and \( q_2 \)) and (\( q_2 \) and \( q_3 \)) are shown in the figure. The charge \( q_2 \) is positive and has the least magnitude. Then: 

An electron is revolving around a proton in an orbit of radius r with a speed v. Obtain an expression for the magnetic moment associated with the electron.

With the help of a diagram, briefly explain the construction and working of an AC generator.

Using Gauss's law, show that the electric field \( E \) at a point due to a uniformly charged infinite plane sheet is given by \( E = \frac{\sigma}{2\epsilon_0} \), where symbols have their usual meanings.

Differentiate between a wavefront and a ray.

Draw a ray diagram for the formation of the image of an object by a convex mirror. Hence, obtain the mirror equation.

A beam of light coming parallel to the principal axis of a convex lens \( L_1 \) of focal length 16 cm is incident on it. Another convex lens \( L_2 \) of focal length 12 cm is placed coaxially at a distance 40 cm from \( L_1 \). The nature and distance of the final image from \( L_2 \) will be:

A thin convex lens \( L \) of focal length 10 cm and a concave mirror \( M \) of focal length 15 cm are placed coaxially 40 cm apart as shown in the figure. A beam of light coming parallel to the principal axis is incident on the lens. The final image will be formed at a distance of: 

The focal length of an equiconvex lens:

A thin converging lens of focal length 20 cm and a thin diverging lens of focal length 15 cm are placed coaxially in contact. The power of the combination is:

An AC voltage \( V = 0.5 \sin (100\pi t) \) volt is applied, in turn, across a half-wave rectifier and a full-wave rectifier. The frequency of the output voltage across them respectively will be:

During the formation of a p-n junction: