List of top Physics Questions asked in CBSE CLASS XII

Define resistivity of a conductor. How does the resistivity of a conductor depend upon the following:

Two isolated metallic spheres $S_1$ and $S_2$ of radii $1 \, \mathrm{cm}$ and $3 \, \mathrm{cm}$ respectively are charged such that both have the same charge density  \[ \sigma = \frac{2}{\pi} \times 10^{-9} \, \mathrm{C/m^2}. \] They are placed far away from each other and connected by a thin wire. Calculate the new charge on sphere $S_1$.
 

An electron is projected from the right plate of set I directly towards its left plate. It just comes to rest at the plate. The speed with which it was projected is about:
(Take \( \frac{e}{m} = 1.76 \times 10^{11} \, C/kg} \))

Three point charges, each of charge \( q \), are placed on vertices of a triangle \( ABC \), with \( AB = AC = 5L \), \( BC = 6L \). The electrostatic potential at the midpoint of side \( BC \) will be:

A plane surface, in the shape of a square of side 1 cm, is placed in an electric field \( \vec{E} = (100 \, \text{N/C}) \hat{i \) such that the unit vector normal to the surface is given by \( \hat{n} = 0.8 \hat{i} + 0.6 \hat{k} \). Find the electric flux through the surface.}

A ray of light passes through a triangular prism. Show graphically how the angle of deviation varies with the angle of incidence. Hence define the angle of minimum deviation

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:

Two identical small conducting balls \( B_1 \) and \( B_2 \) are given \(-7\) \(\mu C\) and \(+4\) \(\mu C\) charges respectively. They are brought in contact with a third identical ball \( B_3 \) and then separated. If the final charge on each ball is \(-2\) \(\mu C\), the initial charge on \( B_3 \) was:

A circular coil of radius 10 cm is placed in a magnetic field \( \vec{B} = (1.0 \hat{i} + 0.5 \hat{j}) \, \text{mT} \) such that the outward unit vector normal to the surface of the coil is \( (0.6 \hat{i} + 0.8 \hat{j}) \). The magnetic flux linked with the coil is:

In normal adjustment, for a refracting telescope, the distance between the objective and 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.

Explain the necessary conditions in which the trajectory of a charged particle is helical in a uniform magnetic field.

What are majority and minority charge carriers in an extrinsic semiconductor?

Two identical point charges are placed at the two vertices A and B of an equilateral triangle of side \( l \). The magnitude of the electric field at the third vertex P is \( E \). If a hollow conducting sphere of radius \( l/4 \) is placed at P, the magnitude of the electric field at point P now becomes:

A battery of e.m.f. 12 V and internal resistance 0.5 \( \Omega \) is connected to a 9.5 \( \Omega \) resistor through a key. The ratio of potential difference between the two terminals of the battery, when the key is open to that when the key is closed, is:

An electron moving with a velocity \( \vec{v} = (1.0 \times 10^7 \, \text{m/s}) \hat{i} + (0.5 \times 10^7 \, \text{m/s}) \hat{j} \) enters a region of uniform magnetic field \( \vec{B} = (0.5 \, \text{mT}) \hat{j} \). Find the radius of the circular path described by it. While rotating, does the electron trace a linear path too? If so, calculate the linear distance covered by it during the period of one revolution.}

A battery supplies 0.9 A current through a 2 \( \Omega \) resistor and 0.3 A current through a 7 \( \Omega \) resistor when connected one by one. The internal resistance of the battery is:

Assertion (A): Plane and convex mirrors cannot produce real images under any circumstance.
Reason (R): A virtual image cannot serve as an object to produce a real image.