List of top Physics Questions asked in UP Board XII

What is meant by displacement current? The amplitude of electric field of an electromagnetic wave is \( E_0 = 120 \, \text{N/C} \) and frequency is \( \nu = 50 \, \text{MHz} \). Find out:
i) Amplitude of the magnetic field \( B_0 \) ii) Wavelength \( \lambda \) of the electromagnetic wave.
What is the first law of Kirchhoff of the electrical circuit? Find out the potential difference between the ends of 2 \(\Omega\) resistor with the help of Kirchhoff's law. See the figure:
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The area of a plane coil 1000 turns is 500 cm\(^2\) and it is held perpendicular to a uniform magnetic field of \(4 \times 10^{-4}\) weber/m\(^2\). It is turned through 180° angle in 0.1 second. Calculate the average induced e.m.f. produced in the coil.
Hydrogen atom in its ground energy state absorbs a photon, which excites it to an energy level of \(n = 4\). Calculate the frequency of photon.
What is the principle of a moving coil galvanometer? Draw its neat labelled diagram. How is the sensitivity of the galvanometer increased?
In between two crossed polaroids A and B, a third polaroid C is placed in such a way that its polarising axis makes an angle \( \theta \) from the polarising axis of the polaroid A. If the intensity of the transmitted light from the polaroid A is \( I_0 \), then find out the intensity of the polarised light transmitted from the polaroid B. For which angle \( \theta \) the intensity of the transmitted light will be maximum?
Enunciate the difference between the conductors and semiconductors on the basis of energy bands in solids.
The stopping potential for the photoelectric current is obtained as 4 V for a metal surface by a monochromatic light of wavelength \( \lambda \), incident on it. The stopping potential becomes \(V\) for the incident light of wavelength \( 2\lambda \) on this surface. Find the formula of threshold wavelength \( \lambda_0 \) in terms of \( \lambda \).
Obtain the formula for the intensity of electric field outside a charged thin spherical shell with the help of Gauss' law.
A \( 4 \, \Omega \) resistance wire is bent into a shape of a circle. What will be the effective resistance between the ends of its diameter?
What is meant by the wattless current?
Write down any two uses of microwaves.
The binding energy per nucleon of \(\alpha\)-particle (\(_2^4\text{He}\)) is 7 MeV. What is its total binding energy?
The unit of coefficient of self-inductance is:
What is Brewster's law?
Write down the unit of magnetic dipole moment.
Following charged particles are projected perpendicular in a uniform magnetic field with the same velocity. The maximum force is exerted on:
Electrons and protons are accelerated by the same potential difference. The ratio of their de Broglie wavelengths is:
n electric dipoles are placed inside a closed surface. Total electric flux linked with the closed surface will be:
The length of the image formed by a concave mirror:
The minority charge carriers in n type of semiconductors:
Explain, the formation of 'Depletion-layer' at the junction p-n junction-diode. Explain potential-barrier and Avalanche breakdown.
What are energy-bands in solids ? Differentiate conductors, insulators and semiconductors on the basis of energy-bands and explain the effect of temperature on these.
What do you mean by Nuclear fission ? In the fission of \(U^{235}\) nucleus, 200 MeV energy is produced. Power of 4 MW is obtained by a reactor. How many nuclei are fissioned per sec in the reactor ?
Focal lengths of objective and eye lenses of a telescope are 40 cm and 4 cm respectively. For an object placed in front of objective lens by 200 cm, what will be the distance between two lenses for normal vision ? Also find its magnification.