List of top Physics Questions asked in UP Board XII

Two parallel plate capacitors of capacitances \( C \) and \( 2C \) are joined with a battery of voltage difference \( V \) as shown in the figure. If the battery is removed and the space between the plates of the capacitor of capacitance \( C \) is completely filled with a material of dielectric constant \( K \), then find out:

• i) Total capacitance of the combination
• ii) Final voltage difference across the combination
• iii) Total energy stored in the combination.

Differentiate between interference and diffraction of light. Explain qualitatively the diffraction phenomenon of light by a single slit. Light of 6000 Ã… wavelength is incident normally on a single slit of width \( 3 \times 10^{-4} \, \text{cm} \). Find out the angular width of the central maxima. 
 

Show that the circumference of the orbit of an electron revolving in the \( n \)-th orbit is equal to \( n\lambda \) with the help of Bohr's quantum theory. Also, show the emission and absorption spectral lines between energy levels \( n = 1 \) and \( n = 3 \) of hydrogen atom. 
 

What do you mean by the current sensitivity of a moving coil galvanometer? Resistance of a galvanometer is \( 50 \, \Omega \) and for full-scale deflection, the current is \( 0.05 \, \mathrm{A} \). What would be the required length of a wire to convert it into an ammeter of 5 A range? (Area of cross-section of wire = \( 2.7 \times 10^{-6} \, \mathrm{m^2} \), specific resistance of the wire material = \( 5.0 \times 10^{-7} \, \Omega \cdot \mathrm{m} \))

Obtain the formula for the internal resistance of a cell in terms of \( E \), \( V \), and \( R \), where \( E \), \( V \), and \( R \) are the electromotive force of the cell, potential difference across the external resistance, and external resistance, respectively.

What is plane polarized light? How is polarized light obtained by refraction? State the uses of polaroid.

Currents of 10 A and 20 A are passed in two long parallel wires A and B, as shown in the figure. A wire C of 15 cm length is placed just in between these two wires, in which 5 A of current is passed. Then what will be the force acting on the wire C? \includegraphics[]{q5 b phy fw.PNG} Calculate: \begin{enumerate} \item Number of turns in the secondary coil, \item Input power. \end{enumerate}

A concave mirror forms a real image 4 times the size of an object. The magnification is 3 times by moving the object 3 cm away from the mirror. Find out the radius of curvature of the mirror.

Define the coefficient of mutual inductance.
The coefficient of mutual inductance (\(M\)) is a measure of the ability of one coil to induce an electromotive force (EMF) in a nearby coil due to a changing current in the first coil. It is given by: \[ e = -M \frac{di}{dt} \]

If a current \( i = 10 \sin(100 \pi t) \, \mathrm{A} \) is flowing in a primary coil, and the maximum induced electromotive force in the secondary coil placed near it is \( 5 \pi \, \mathrm{volt} \), then the coefficient of mutual induction between these coils needs to be determined.

A graph is shown between the maximum kinetic energy (\( E_k \)) of emitted photoelectrons and frequency (\( \nu \)) of the incident light in an experiment of the photoelectric effect. Find:
(i) Threshold frequency
(ii) Work function (in eV)
(iii) Planck's constant \includegraphics[]{q4 d phy fw.PNG}

What is Biot-Savart law? Obtain the formula and direction for the intensity of the magnetic field on the axis of an anti-clockwise current-carrying loop with its help.

What are electromagnetic waves? Explain two characteristics of these waves.

A charge \( Q \) is distributed over two concentric hollow spheres of radii \( r \) and \( R \) (\( R>r \)) such that their surface charge densities are equal. Find the electric potential at their common center.

A current is passed in a wire of \( 4 \, \Omega \) resistance by a battery. Find out the internal resistance of the battery, when current is passed in another \( 9 \, \Omega \) resistor by the same battery; while the same heat is produced during the same time in both wires. 
 

If the corresponding de Broglie wavelengths of a proton and a neutron are obtained as same, then which of the two will have greater kinetic energy? 
 

State the conclusions of Rutherford's \( \alpha \)-particle scattering experiment. 
 

 Explain the energy bands in solids. 
 

What is the main difference between paramagnetic and ferromagnetic substances? 
 

The amplitude of the magnetic field of an electromagnetic wave in vacuum is \(B_0 = 510 \, \text{nT}\). What is the amplitude of the electric field of the wave? 
 

Find out the angle of refraction in a medium of refractive index \(\sqrt{3}\), when the angle of incidence is \(60^\circ\). 
 

What is meant by the depletion layer in a \(p\)-\(n\) junction? 
 

What is Lenz’s law? 
 

What is the magnitude of the current \( i \) in the given circuit? 
\includegraphics[]{q2a phy fw.PNG}

The sides of two solid cubes of the same material are \(l\) and \(3l\) respectively. The ratio of their resistances will be: