List of top Physics Questions asked in CBSE CLASS XII

Radiation of wavelength \(331\ \text{nm}\) irradiates the following metals :
Which of the following statements is correct ?
While studying photoelectric emission from a given surface, the wavelength of the incident radiation is changed from \(600\,\text{nm}\) to \(400\,\text{nm}\), keeping the intensity of radiation the same. Then :
The kinetic energy of a charged particle is increased to four times of its initial value. The de Broglie wavelength associated with the particle will :
In a reversed-biased p-n junction diode, the applied voltage mostly drops across :
The ratio of amplitude of electric field to the amplitude of the magnetic field associated with an electromagnetic wave propagating in glass \((n=1.5)\) is :
Paschen series in spectrum of hydrogen atom lies in :
The dimensions of the rate of change of magnetic flux are :
An ac voltage is given as \(v = 14\sin(314t)\,\text{V\). The average and the effective value of the voltage (in V) over a cycle are respectively :}
Two wires of same length and same area of cross-section but made of different materials of resistivities \( \rho_1 \) and \( \rho_2 \) are connected in series. The equivalent resistivity of the combination is :
Two particles of masses \(m_1\) and \(m_2\) having charges \(q_1\) and \(q_2\) respectively are projected with the same velocity in a region of uniform magnetic field \(\vec{B}\) pointing vertically upward. If they describe circular paths as shown in the figure, one may conclude that :
An electron moves around the nucleus in a circular orbit of radius \(r\) and makes \(n\) revolutions per second. The value of equivalent current in the orbit is :
Two identical conductors 1 and 2 are placed on two frictionless conducting rails R and S in a uniform magnetic field directed vertically downward into the plane of the page. If conductor 1 is moved with a constant velocity in the direction as shown in figure, the force on conductor 2 will be along :

A parallel beam of monochromatic light falls normally on a single slit of width \( a \) and a diffraction pattern is observed on a screen placed at a distance \( D \) from the slit. Explain:
the formation of maxima and minima in the diffraction pattern, and
why the maxima go on becoming weaker and weaker with increasing order \( (n) \).
Depict the variation of electric field (\(\vec{E}\)) and magnetic field (\(\vec{B}\)) with respect to the direction of propagation of an electromagnetic wave. Write their two important characteristics.
What is the phase relation between current and voltage in an ideal inductor connected to an ac source? Draw a phasor diagram for the circuit.
Show that \(\frac{1}{\sqrt{\mu_0 \varepsilon_0}}\) gives the velocity of an electromagnetic wave in free space.
A circular coil of 30 turns and radius 8·0 cm carrying a current of 6 A is suspended vertically in a uniform horizontal magnetic field of 1·0 T. The field lines make an angle of 30\(^{\circ}\) with the plane of the coil. Calculate the magnitude of the external torque that must be applied to prevent the coil from turning. What would happen if the circular coil is replaced by a planar coil of irregular shape that encloses the same area, keeping other parameters unchanged?
An alpha particle (mass \(6.4 \times 10^{-27} \text{ kg}\) and charge \(3.2 \times 10^{-19} \text{ C}\)) having \(8.0 \text{ MeV}\) energy, enters a region of a uniform magnetic field of \(0.5 \text{ T}\). If the field is directed perpendicular to the velocity of the particle, find the radius of the circular path described by the particle. Mention the condition under which the particle in this region (i) describes a helical path, and (ii) goes straight undeviated.
How is \(v_d\) affected when the length of the conductor is doubled, keeping the voltage applied across the conductor constant?
Establish the relation between drift velocity of electrons (\(v_d\)) and electric current (\(I\)) in a conductor.
How are charge carriers created in an intrinsic semiconductor? Explain.
A particle of mass \(M\) at rest splits up into two particles of masses \(m_1\) and \(m_2\) having non-zero velocities. Calculate the ratio of the de Broglie wavelengths associated with the two particles.
Discuss the behaviour of an inductor connected to (i) a dc source, and (ii) a high frequency ac source.
Explain the terms mass defect and binding energy. How are they related?
In the given figure, a steady current \(I\) flows through the circuit when points A and C are connected by a wire of negligible resistance. Find the potential difference between points B and C.