List of top Physics Questions asked in CBSE CLASS XII

\( n \) identical cells, each of e.m.f \( E \) and internal resistance \( r \), are connected in series. Later on, it was found that two cells ‘X’ and ‘Y’ are connected in reverse polarities. Calculate the potential difference across the cell ‘X’.
In a Young’s double-slit experiment, two light waves, each of intensity \( I_0 \), interfere at a point, having a path difference \( \frac{\lambda}{8} \) on the screen. Find the intensity at this point.
The alternating current \( I \) in an inductor is observed to vary with time \( t \) as shown in the graph for a cycle.
alternating current I in an inductor

Which one of the following graphs is the correct representation of wave form of voltage \( V \) with time \( t \)?}
A diamagnetic substance is brought, one by one, near the north pole and the south pole of a bar magnet. It is:
Two long solenoids of radii \( r_1 \) and \( r_2 \) (\( > r_1 \)) and number of turns per unit length \( n_1 \) and \( n_2 \) respectively are co-axially wrapped one over the other. The ratio of self-inductance of inner solenoid to their mutual inductance is:
A 1 cm straight segment of a conductor carrying 1 A current in \( x \)-direction lies symmetrically at the origin of Cartesian coordinate system. The magnetic field due to this segment at point (1m, 1m, 0) is:
A coil of an AC generator, having 100 turns and area 0.1 m² each, rotates at half a rotation per second in a magnetic field of 0.02 T. The maximum emf generated in the coil is:
Atomic spectral emission lines of hydrogen atom are incident on a zinc surface. The lines which can emit photoelectrons from the surface are members of:
The focal length of a concave mirror in air is \( f \). When the mirror is immersed in a liquid of refractive index \( \frac{3}{5} \), its focal length will become:
Which one of the following statements is correct? Electric field due to static charges is:
When the resistance measured between p and n ends of a p-n junction diode is high, it can act as a/an:
The energy of an electron in a hydrogen atom in ground state is -13.6 eV. Its energy in an orbit corresponding to quantum number \( n \) is -0.544 eV. The value of \( n \) is:
Assertion : Out of Infrared and radio waves, the radio waves show more diffraction effect. Reason (R): Radio waves have greater frequency than infrared waves.
Assertion : In an ideal step-down transformer, the electrical energy is not lost. Reason (R): In a step-down transformer, voltage decreases but the current increases.
Assertion : In Bohr model of hydrogen atom, the angular momentum of an electron in \( n \)th orbit is proportional to the square root of its orbit radius \( r_n \). Reason (R): According to Bohr model, electron can jump to its nearest orbits only.
Assertion : In a semiconductor diode, the thickness of the depletion layer is not fixed. Reason (R): Thickness of depletion layer in a semiconductor device depends upon many factors such as biasing of the semiconductor.
The threshold voltage of a silicon diode is 0.7 V. It is operated at this point by connecting the diode in series with a battery of \( V \) volt and a resistor of 1000 \( \Omega \). Find the value of \( V \) when the current drawn is 15 mA.
Show the refraction of light wave at a plane interface using Huygens' principle and prove Snell's law.
Two convex lenses A and B, each of focal length 10.0 cm, are mounted on an optical bench at 50.0 cm and 70.0 cm respectively. An object is mounted at 20.0 cm. Find the nature and position of the final image formed by the combination.
Radiations of two frequencies are incident on a metal surface of work function 2.0 eV one by one. The energies of their photons are 2.5 eV and 4.5 eV respectively. Find the ratio of the maximum speed of the electrons emitted in the two cases.
Two wires of the same material and the same radius have their lengths in the ratio 2:3. They are connected in parallel to a battery which supplies a current of 15 A. Find the current through the wires.
In the circuit, three ideal cells of e.m.f. \( V \), \( V \), and \( 2V \) are connected to a resistor of resistance \( R \), a capacitor of capacitance \( C \), and another resistor of resistance \( 2R \) as shown in the figure. In the steady state, find (i) the potential difference between P and Q, (ii) the potential difference across capacitor C.
potential difference across capacitor C
Define resistivity of a conductor. Discuss its dependence on temperature of the conductor and draw a plot of resistivity of copper as a function of temperature.
"A low voltage battery from which high current is required must have low internal resistance." Justify.
"A high voltage battery must have a large internal resistance." Justify.