Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Physics

Derive an expression for voltage gain of the amplifier and hence show that the output voltage is in opposite phase with the input voltage.

How is linearly polarised light obtained by the process of scattering of light. Find the Brewster angle for air – glass interface, when the refractive index of glass = 1.5. 

Find the ratio of the potential differences that must be applied across the parallel and series combination of two capacitors C₁ and C₂ with their capacitances in the ratio 1 : 2 so that the energy stored in the two cases becomes the same.

An infinitely large thin plane sheet has a uniform surface charge density +σ. Obtain the expression for the amount of work done in bringing a point charge q from infinity to a point, distant r, in front of the charged plane sheet. 

Distinguish between unpolarized light and linearly polarized light

Draw a circuit diagram for studying the input and output characteristics of a n-p-n transistor in common emitter configuration. Using the circuit, explain how input, output characteristics are obtained

Draw a graph showing the variation of intensity (I) of polarised light transmitted by an analyzer with the angle (θ) between polariser and analyzer.

A bar magnet of magnetic moment 6 J/T is aligned at 60° with a uniform external magnetic field of 0·44 T Calculate  

a) the work done in turning the magnet to align its magnetic moment

i) normal to the magnetic field, 

ii) opposite to the magnetic field, and

b)  the torque on the magnet in the final orientation in case (ii).

Using Gauss's law in electrostatics, deduce an expression for electric field intensity due to a uniformly charged infinite plane sheet. If another identical sheet is placed parallel to it, show that there is no electric field in the region between the two sheets ?

A point object is placed on the principal axis of a convex spherical surface of radius of curvature R, which separates the two media of refractive indices n₁ and n₂ (n₂ > n₁). Draw the ray diagram and deduce the relation between the object distance (u), image distance (v) and the radius of curvature (R) for refraction to take place at the convex spherical surface from rarer to denser medium.

Distinguish between polarized and unpolarized light. Does the intensity of polarized light emitted by a polaroid depend on its orientation? Explain briefly.
The vibration in a beam of polarized light make an angle of 60° with the axis of the polaroid sheet. What percentage of light is transmitted through the sheet?

Describe the working principle of a solar cell. Mention three basic processes involved in the generation of emf.

Why are Si and GaAs preferred materials for solar cells?

Gautam went for a vacation to the village where his grandmother lived. His grandmother took him to watch 'nautanki' one evening. They noticed a blackbox connected to the mike lying nearby. Gautam's grandmother did not know what that box was. When she asked this question to Gautam, he explained to her that it was an amplifier.
(i) Which values were displayed by the grandmother? How can inculcation of these values in students be promoted?
(ii) What is the function of an amplifier?
(iii) Which basic electronic device is used in the amplifier?

Why is potentiometer preferred over a voltmeter for comparison of emf. of cells?

A small conducting sphere of radius 'r' carrying a charge +q is surrounded by a large concentric conducting shell of radius Ron which a charge +Q is placed. Using Gauss's law, derive the expressions for the electric field at a point 'x'
(i) between the sphere and the shell (r < x < R),
(ii) outside the spherical shell.

A circuit is set up by connecting inductance L = 100 mH, resistor R = 100 Ω and a capacitor of reactance 200 Ω in series. An alternating emf of \[150\sqrt{2}\]  V, 500/π Hz is applies across this series combination. Calculate the power dissipated in the resistor.

Distinguish between unpolarised and linearly polarised light.

A partially plane polarised beam of light is passed through a polaroid. Show graphically the variation of the transmitted light intensity with angle of rotation of the polaroid ?

Explain with the help of a diagram how sunlight is polarised by scattering through atmospheric particles ?