List of top Questions asked in CBSE CLASS XII

Organising provides a clear description of jobs and related duties. This helps to avoid confusion and duplication. The point of importance of organizing described above is:
High inflation rates generally result in constraints on business enterprises as they increase the various costs of business such as the purchase of raw materials and payment of wages and salaries to employees, etc. The dimension of business environment referred to above is:
Statement-I: Motivation is a complex process as individuals are heterogeneous in their expectations, perceptions, and reactions. Statement-II: Motivation can be either positive or negative. Choose the correct option from the following:
A charged particle is moving in a circular path with velocity \( V \) in a uniform magnetic field \( \vec{B} \). It is made to pass through a sheet of lead and as a consequence, it looses one half of its kinetic energy without change in its direction. How will (1) the radius of its path change? (2) its time period of revolution change?
Derive an expression for the torque acting on a rectangular current loop suspended in a uniform magnetic field.
Define a wavefront. An incident plane wave falls on a convex lens and gets refracted through it. Draw a diagram to show the incident and refracted wavefront.
A system of two conductors is placed in air and they have net charge of \( +80 \, \mu C \) and \( -80 \, \mu C \) which causes a potential difference of 16 V between them.
(1) Find the capacitance of the system.
(2) If the air between the capacitor is replaced by a dielectric medium of dielectric constant 3, what will be the potential difference between the two conductors?
(3) If the charges on two conductors are changed to +160µC and −160µC, will the capacitance of the system change? Give reason for your answer.
A current carrying circular loop of area A produces a magnetic field \( B \) at its centre. Show that the magnetic moment of the loop is \( \frac{2BA}{\mu_0} \sqrt{\frac{A}{\pi}} \).
Two point charges \( 5 \, \mu C \) and \( -1 \, \mu C \) are placed at points \( (-3 \, \text{cm}, 0, 0) \) and \( (3 \, \text{cm}, 0, 0) \) respectively. An external electric field \( \vec{E} = \frac{A}{r^2} \hat{r} \) where \( A = 3 \times 10^5 \, \text{V/m} \) is switched on in the region. Calculate the change in electrostatic energy of the system due to the electric field.
A beam of light coming from a distant source is refracted by a spherical glass ball (refractive index 1.5) of radius 15 cm. Draw the ray diagram and obtain the position of the final image formed.
A proton moving with velocity \( V \) in a non-uniform magnetic field traces a path as shown in the figure. The path followed by the proton is always in the plane of the paper. What is the direction of the magnetic field in the region near points P, Q, and R? What can you say about relative magnitude of magnetic fields at these points?
proton moving with velocity V in a non-uniform magnetic field
A charge \( -6 \mu C \) is placed at the center B of a semicircle of radius 5 cm, as shown in the figure. An equal and opposite charge is placed at point D at a distance of 10 cm from B. A charge \( +5 \mu C \) is moved from point ‘C’ to point ‘A’ along the circumference. Calculate the work done on the charge.
work done on the charge
Lights from two independent sources are not coherent. Explain.
Two slits 0.1 mm apart are arranged 1.20 m from a screen. Light of wavelength 600 nm from a distant source is incident on the slits.
Find the angular width (in degrees) of the first bright fringe.
Two slits 0.1 mm apart are arranged 1.20 m from a screen. Light of wavelength 600 nm from a distant source is incident on the slits. How far apart will adjacent bright interference fringes be on the screen?
What are coherent sources? Why are they necessary for observing a sustained interference pattern?
A deuteron contains a proton and a neutron and has a mass of 2.013553 u. Calculate the mass defect for it in u and its energy equivalence in MeV.
Given:
\( m_p = 1.007277 \) u, \( m_n = 1.008665 \) u, \( 1 \) u = \( 931.5 \) MeV/\( c^2 \).
Define ‘Mass defect’ and ‘Binding energy’ of a nucleus. Describe ‘Fission process’ on the basis of binding energy per nucleon.
Mention two information that you can get fromV-I characteristics of a p-n junction diode.
In his experiment on photoelectric effect, Robert A. Millikan found the slope of the cut-off voltage versus frequency of incident light plot to be \( 4.12 \times 10^{-15} \, \text{Vs} \). Calculate the value of Planck’s constant from it.
A parallel plate capacitor is charged by an ac source. Show that the sum of conduction current (\( I_c \)) and the displacement current (\( I_d \)) has the same value at all points of the circuit.
Draw circuit arrangement for studying V-I characteristics of a p-n junction diode.
A parallel plate capacitor is charged by an ac source, Kirchhoff's first rule (junction rule) valid at each plate of the capacitor? Explain.
Show the shape of the characteristics of a diode.
Mention any three features of results of experiment on photoelectric effect which cannot be explained using the wave theory of light.