List of top Questions asked in UP Board XII- 2026

State the working principle of a transformer and mention the energy losses occurring in it.
In which the power of a lens will be large, in air or water?
The work function of a metal is 3.3 eV. Calculate the minimum frequency of photon that will emit the photoelectron.
(Given: \( h = 6.6\times10^{-34} \) J·s, \( 1\ \text{eV} = 1.6\times10^{-19} \) J)

The variation between V and I with time (t) in two alternative circuits is shown in the above graphs. Which one of the curves of circuit is capacitive and which one is resistive?
An electron of energy 10 eV is revolving round a circular path in a uniform magnetic field of \( 10^{-5} \) tesla. Determine the radius of the circular path.
(Given: mass of electron \( m = 9.1\times10^{-31} \) kg, charge \( e = 1.6\times10^{-19} \) C)
By giving the examples, explain the meaning of diamagnetic and paramagnetic materials.
Write the definitions of electrical conductivity and specific conductivity.
Among the following, the electromagnetic wave of minimum frequency is:
In Rutherford's scattering experiment, the path of a scattered \( \alpha \)-particle is:
The number of electrons that must be removed from a piece of metal to give it a charge of \( 1\times10^{-7} \) coulomb will be:
In the depletion layer of a p-n junction diode, there are:
The unit of \( \sqrt{LC} \) (where \( L \) is inductance and \( C \) is capacitance) is:
If the critical angle in a medium is \( \alpha \), then for total internal reflection the angle of incidence \( \beta \) should be:
Define electromotive force of a cell.
Derive the formula for energy loss on connecting two charged conductors through a conducting wire.
OR
Explain the meaning of polarization of a dielectric material. What will be the effect on the capacity of an air filled parallel plate capacitor on putting a dielectric material in between its plates? Equivalent capacity of two condensers in series is 7.5 µF and in parallel is 30 µF. What will be the capacity of both the capacitors separately?
Explain the difference between conductor, insulator and semiconductor on the basis of energy band in solids.
OR
Define diamagnetic, paramagnetic and ferromagnetic materials. Explain that a current carrying solenoid behaves as a bar magnet.
Write Huygen's principle of secondary wavelets and verify laws of refraction on its basis.
OR
Explain the meaning of coherent sources and sustained interference. Why central fringe in Young's double slit experiment is always bright? In Young's double slit experiment, fringe width is 0.04 cm for light of 6000 Å. Distance of screen from slits is 1 m. Find the distance of third bright and second dark fringe from central fringe and also the separation between the slits.
Derive the formula for magnetic field due to an infinitely long current carrying conducting wire using Biot-Savart law.
OR
Differentiate between self-induction and mutual induction. The current in primary coil becomes zero in \(10^{-3}\) s and an induced e.m.f. of 1500 volts is produced in secondary. Mutual inductance of coils is 0.5 H. Find the value of initial current in the primary.
Potential difference at the ends of a conductor of length \(l\) is \(V\). Diameter of the conductor is \(d\). What will be the effect on the electric field inside the conductor and its resistance, if (i) \(V\) is halved? (ii) \(l\) is doubled? (iii) \(d\) is doubled?
What are electromagnetic waves? An electromagnetic wave is moving in the X direction and the directions of its electric and magnetic fields are Y and Z respectively. Write the general equations for the electric and magnetic fields of the wave. How are electromagnetic waves different from sound waves?
Reflecting telescopes are supposed to be better than refracting telescopes. Why? Draw the ray diagram for image formation by a refracting telescope. Final image is formed at infinity.
OR
What is the meaning of polarisation of light? Whether sound waves are also polarized? Explain polarization of light by refraction.
Explain the effect of biasing on the depletion region of a p-n junction. Using a p-n junction diode, draw the circuit diagram of a half-wave rectifier and show the shape of the input and output voltage.
For any particle, its particle nature and wave nature can be observed simultaneously. Comment. Radiation of wavelength \( \lambda \) is incident on a surface of negligible work function. Find the de-Broglie wavelength of the emitted electron.
Find the formula for the work done in rotating a magnetic dipole in a uniform magnetic field through an angle \( \theta \). What will be the work done in rotating a magnetic dipole lying parallel to the magnetic field by an angle of \( 180^\circ \)?
Explain Kirchhoff's laws related to electrical circuits.