CBSE 2025, Compartment, Set 1 Solutions
CBSE Physics (2025)

A small metallic sphere S of charge $+q$ is placed exactly at a point midway between two-point charges $A(+Q)$ and $B(+Q)$ where $Q>>q$. If the sphere is slightly displaced towards charge A and released, then :

In a Rutherford scattering experiment, when an alpha particle of mass $m_1$ approaches a target nucleus of charge $Ze$ and mass $m_2$ the distance of the closest approach is $d_0$. The energy of the particle is :

The potential energy of a pair of nucleons is minimum when they are separated by about :

The figure shows the variation of maximum kinetic energy $K_{max}$ of emitted electrons as a function of the frequency $\nu$ of radiation incident on a photosensitive surface. The slope of the curve is :

Whenever a magnet is moved either towards or away from a conducting coil, an emf is induced whose magnitude is independent of the :

Electromagnetic radiation used to kill germs in water purifiers is :

A galvanometer having a coil resistance of $48 \Omega$ shows full-scale deflection for a current of $2.0\text{ A}$. It can be converted into an ammeter of range $(0-10\text{ A})$ by connecting :

A rectangular loop of area vector $\vec{A} = [\hat{i} + \sqrt{3}\hat{j}] \times 10^{-2}\text{ m}^2$ is placed in a magnetic field $\vec{B} = [4.0t^2 + 2.0]\hat{i}$, where $B$ is in tesla and $t$ in seconds. At $t = 1.0\text{ s}$, the magnitude of induced emf in the loop is :

A charge $Q$ is enclosed by a spherical Gaussian surface of radius $R$. If the radius is doubled, then the total electric flux through the surface :

The average value of voltage of $220\text{ V}$ ac mains during its positive half cycle will be :

Two parallel beams of protons moving in the same direction will :

Which of the following assumptions has been used to obtain the relation $\frac{v_s}{v_p} = \frac{N_s}{N_p}$ for a transformer ?

Assertion (A): Electrostatic force is a conservative force. Reason (R): In an electrostatic field, the work done between two points per unit positive charge depends on the path followed.

Select the correct option:

Assertion (A): The image of an object placed between $f$ and $2f$ from a convex lens can be seen on a screen. If the screen is removed, image is not formed. Reason (R): Rays from a given point on the object placed between $f$ and $2f$, after passing through a convex lens, do not converge on a point in space.

Select the correct option:

Assertion (A): In process of photoelectric emission using a monochromatic light, all emitted electrons do not have the same kinetic energy. Reason (R): If radiation falling on a photosensitive surface consists of different wavelengths, the energy of emitted photoelectrons by absorbing photons of different wavelengths, shall be different.

Select the correct option:

Assertion (A): The electrical conductivity of a pure Ge crystal increases with increase in its temperature. Reason (R): The number of electrons excited by thermal excitation from the valence band to the conduction band, in a semiconductor, increases with increase in temperature.

Select the correct option:

The work function of Caesium is $2.14\text{ eV}$. Find the wavelength of the incident light if the photocurrent is brought to zero by a stopping potential of $0.86\text{ V}$.

The work function of Caesium is $2.14\text{ eV}$. Find the threshold frequency for Caesium.

A plano-convex lens of refractive index $\mu_1$ is placed coaxially in contact with a biconcave lens of refractive index $\mu_2$ as shown in the figure. All curved faces are of radius of curvature $R$ each. Obtain the expression for the focal length of the combined lens.

A convex lens is kept coaxially on the left side of a concave mirror at a distance of $5f$ from it where $f$ is focal length of each of them. An object is kept at a distance of $2f$ on the left side of the convex lens. Find the distance of the final image from the mirror.

The figure shows a network of resistors connected across a battery. Find the current supplied by the battery of emf $5\text{ V}$ and internal resistance $\frac{2}{3} \Omega$.

With the help of a circuit diagram, describe the method to obtain p-n junction diode characteristic when it is forward biased. Draw the shape of the characteristic.

Light of wavelength $640\text{ nm}$ incident on the slits in a Young's double-slit experiment produces an interference pattern of fringe width $7.2\text{ mm}$. Calculate the wavelength of light which will produce a pattern of fringe width $8.1\text{ mm}$.