CBSE Class 12 Physics Last 5 + 1 Years’ Very Long Answer Type Questions
Get CBSE class 12 Physics previous 5 + 1 years’ very long answer type questions. These questions are important for CBSE Class 12 Physics board exam 2017.
CBSE class 12 Physics previous 5 + 1 years’ very long answer type questions are available in this article.
As per latest examination pattern, 4 long answer type questions will be asked in CBSE class 12 Physics exam 2017. Out of 4 questions, 1 will be (value based question) of four marks and rest 3 will be of five marks.
Before the year 2015, the examination pattern of CBSE Class 12 Physics board exam was quite different.
However, in order to understand the level of questions which can be asked in CBSE class 12 Physics exam 2017, students of CBSE class 12 must go through these previous year questions.
CBSE Class 12 Physics Sample Paper 2017
The solutions of these questions are available in CBSE Class 12th Solved Previous Years' Papers (Last 5+ 1 years') PCM - eBook
Questions from previous year papers are given below:
CBSE Class 12 Physics Board Exam 2016: Very Long Answer Type Questions (4 Marks & 5 Marks) |
Q. Ram is a student of class X in a village school. His uncle gifted him a bicycle with a dynamo fitted in it. He was very excited to get it. While cycling during night, he could light the bulb and see the objects on the road. He, however, did not know how this device works. He asked this question to his teacher. The teacher considered it an opportunity to explain the working to the whole class. Answer the following questions: (a) State the principle and working of a dynamo. (b) Write two values each displayed by Ram and his school teacher. |
Q. (i) Use Gauss's law to find the electric field due to a uniformly charged infinite plane sheet. What is the direction of field for positive and negative charge densities? (ii) Find the ratio of the potential differences that must be applied across the parallel and series combination of two capacitors C_{1 }and C_{2} with their capacitances in the ratio 1:2 so that the energy stored in the two cases becomes the same. OR Q. (i) If two similar large plates, each of area A having surface charge densities + σ and ‒σ are separated by a distance d in air, find the expressions for (a) field at points between the two plates and on outer side of the plates. Specify the direction of the field in each case. (b) the potential difference between the plates. (c) the capacitance of the capacitor so formed. (ii) Two metallic spheres of radii R and 2R are charged so that both of these have same surface charge density σ. If they are connected to each other with a conducting wire, in which direction will the charge flow and why? |
Q. (i) Draw a labelled diagram of a step-down transformer. State the principle of its working. (ii) Express the turn ratio in terms of voltages. (iii) Find the ratio of primary and secondary currents in terms of turn ratio in an ideal transformer. (iv) How much current is drawn by the primary of a transformer connected to 220 V supply when it delivers power to a 110 V ‒ 550 W refrigerator? OR Q. (a) Explain the meaning of the term mutual inductance. Consider two concentric circular coils, one of radius r_{1} and the other of radius r_{2 }(r_{1}<r_{2}) placed coaxially with centres coinciding with each other. Obtain the expression for mutual inductance of the arrangement. (b)A rectangular coil of area A, having number of turns N is rotated at ‘f’ revolution per second in a uniform magnetic field B, the field being perpendicular to the coil. Prove that the maximum emf induced in the coil is 2πf NBA. |
Q. (i) Derive the mathematical relation between refractive indices n_{1} and n_{2} of two radii and radius of curvature R for refraction at a convex spherical surface. Consider the object to be a point since lying on the principle axis in rarer medium of refractive index n_{1} and a real image formed in the denser medium of refractive index n_{2}. Hence, derive lens maker's formula. (ii) Light from a point source in air falls on a convex spherical glass surface of refractive index 1.5 and radius of curvature 20 cm. The distance of light source from the glass surface is 100 cm. At what position is the image formed? OR Q. (a) Draw a labelled ray diagram to obtain the real image formed by an astronomical telescope in normal adjustment position. Define its magnifying power. (b) You are given three lenses of power 0.5 D, 4 D and 10 D to design a telescope. (i) Which lenses should he used as objective and eyepiece? Justify your answer. (ii) Why is the aperture of the objective preferred to be large? |
CBSE Class 12 Physics Board Exam 2015: Long Answer Type Questions (4 Marks and 5 Marks) |
Q. Ajit had a high tension tower erected on his farm land. He kept complaining to the authorities to remove it as it was occupying a large portion of his land. His uncle, who was a teacher, explained to him the need for erecting these towers for efficient transmission of power. As Ajit realised its significance, he stopped complaining. Answer the following questions: (a) Why is it necessary to transport power at high voltage? (b) A low power factor implies large power loss. Explain. (c) Write two values each displayed by Ajit and his uncle. |
Q. (a) Define self-inductance of a coil. Obtain an expression for the energy stored in a solenoid of self-inductance ‘L’ when the current though it grows from zero to ‘I’. (b) A square loop MNOP of side 20 cm is placed horizontally in a uniform magnetic field acting vertically downwards as shown in the figure. The loop is pulled with a constant velocity of 20 cm s^{−1} till it goes out of the field. (i) Depict the direction of the induced current in the loop as it goes out of the field. For how long would the current in the loop persist? (ii) Plot a graph showing the variation of magnetic flux and induced emf as a function of time. OR (a) Draw the magnetic field lines due to a circular loop area A carrying current I. Show that it acts as a bar magnet of magnetic moment m = I A. (b) Derive the expression for the magnetic field due to a solenoid of length ‘2l’, radius ‘a’ having ’n’ number of turns per unit length and carrying a steady current ‘I’ at a point on the axial line, distance ‘r’ from the centre of the solenoid. How does this expression compare with the axial magnetic field due to a bar magnet of magnetic moment ‘m’? |
(a) In young’s double slit experiment, deduce the conditions for obtaining constructive and destructive interference fringes. Hence, deduce the expression for the fringe width. (b) Show that the fringe pattern on the screen is actually a superposition of slit diffraction from each slit. (c) What should be the width of each slit to obtain 10 maxima of the double slit pattern within the central maximum of the single slit pattern, for green light of wavelength 500 nm, if the separation between two slits is 1 mm? OR (a) Two thin convex lenses L_{1} and L2 of focal lengths f1 and f2, respectively, are placed coaxially in contact. An object is placed at a point beyond the focus of lens L1. Draw a ray diagram to show the image formation by the combination and hence derive the expression for the focal length of the combined system. (b) A ray PQ incident on the face AB of a prism ABC, as shown in the figure, emerges from the face AC such that AQ = AR. Draw the ray diagram showing the passage of the ray through the prism. If the angle and refractive index of the material of prism is 60°of the prism is √3, determine the values of angle of incidence and angle of deviation. |
Q. (a) Deduce the expression for the potential energy of a system of two charges q_{1} and q_{2} located r_{1} and r_{2} , respectively, in an external electric field. (b) Three point charges, + Q, + 2Q and – 3Q are placed at the vertices of an equilateral triangle ABC of side l. If these charges are displaced to the mid-point A_{1}, B_{1} and C_{1}, respectively, find the amount of the work done in shifting the charges to the new locations. OR Define electric flux. Write its S.I unit. State and explain Gauss’s law. Find out the outward flux to a point charge + q placed at the centre of a cube of side ‘a’. Why is it found to be independent of the size and shape of the surface enclosing it? Explain. |
CBSE Class 12 Physics Board Exam 2014: Long Answer Type Questions (5 Marks) |
Q. Draw a labelled diagram of Van de Graaff generator. State its working principle to show how by introducing a small charged sphere into a larger sphere, a large amount of charge can be transferred to the outer sphere. State the use of this machine and also point out its limitations. OR (a) Deduce the expression for the torque acting on a dipole of dipole moment p in the presence of a uniform electric field E. |
Q. (a) In Young's double slit experiment, describe briefly how bright and dark fringes are obtained on the screen kept in front of a double slit. Hence obtain the expression for the fringe width. (b) The ratio of the intensities at minima to the maxima in the Young's double slit experiment is 9 : 25. Find the ratio of the widths of the two slits. OR (a) Describe briefly how a diffraction pattern is obtained on a screen due to a single narrow slit illuminated by a monochromatic source of light. Hence obtain the conditions for the angular width of secondary maxima and secondary minima. (b) Two wavelengths of sodium light of 590 nm and 596 nm are used in turn to study the diffraction taking place at a single slit of aperture 2 × 10^{−6} m. The distance between the slit and the screen is 1·5 m. Calculate the separation between the positions of first maxima of the diffraction pattern obtained in the two cases. |
Q. (a) Deduce an expression for the frequency of revolution of a charged particle in a magnetic field and show that it is independent of velocity or energy of the particle. (b) Draw a schematic sketch of a cyclotron. Explain, giving the essential details of its construction, how it is used to accelerate the charged particles. OR (a) Draw a labelled diagram of a moving coil galvanometer. Describe briefly its principle and working. (b) Answer the following: (i) Why is it necessary to introduce a cylindrical soft iron core inside the coil of a galvanometer? (ii) Increasing the current sensitivity of a galvanometer may not necessarily increase its voltage sensitivity. Explain, giving reason. |
CBSE Class 12 Physics Board Exam 2013: Long Answer Type Questions (5 Marks) |
Q. (a) Using Biot – Savart’s law, derive the expression for the magnetic field in the vector form at a point on the axis of a circular current loop. (b) What does a toroid consist of? Find out the expression for the magnetic field inside a toroid for N turns of the coil having the average radius r and carrying a current I. Show that the magnetic field in the open space inside and exterior to the toroid is zero. OR (a) Draw a schematic sketch of a cyclotron. Explain clearly the role of crossed electric and magnetic field in accelerating the charge. Hence derive the expression for the kinetic energy acquired by the particles. (b) An α-particle and a proton are released from the centre of the cyclotron and made to accelerate. (i) Can both be accelerated at the same cyclotron frequency? Give reason to justify your answer. (ii) When they are accelerated in turn, which of the two will have higher velocity at the exit slit of the does? |
Q. (a) Define electric dipole moment. Is it a scalar or a vector? Derive the expression for the electric field of a dipole at a point on the equatorial plane of the dipole? (b) Draw the equipotential surface due to an electric dipole. Locate the points where the potential due to the dipole is zero? OR Using Gauss’ law deduce the expression for the electric field due to a uniformly charged spherical conducting shell of radius R at a point (i) outside and (ii) inside the shell. Plot a graph showing variation of electric field as a function of r > R and r < R (r being the distance from the centre of the shell). |
Q. Using Bhor’s postulates derive the expression for the frequency of radiation emitted when electron in hydrogen atom undergoes transition from higher energy state (Quantum number n_{i}) to the lower. (n_{f}). When electron in hydrogen atom jumps from state n_{i} = 4 to n_{f} = 3, 2, 1, identify the spectral series to which the emission lines below. OR (a) Draw the plot of binding energy per nuclear (BE/A) as a function of mass number A. Write two important conclusions that can be drawn regarding the nature of nuclear force? (b) Use this graph to explain the release of energy in both the processes of nuclear fusion and fusion? (c) Write the basic nuclear process of neutron undergoing β – decay. Why is the detection of neutrinos found very difficult? (b) Use this graph to explain the release of energy in both the processes of nuclear fusion and fusion? (c) Write the basic nuclear process of neutron undergoing β – decay. Why is the detection of neutrinos found very difficult? |
CBSE Class 12 Physics Board Exam 2012: Long Answer Type Questions (5 Marks) |
Q. (a) In Young's double slit experiment, derive the condition for (i) constructive interference and (ii) destructive interference at a point on the screen. (b)A beam of light consisting of two wavelength, 800 nm and 600 nm is used to obtain the interference fringes in a Young's double slit experiment on a screen placed 1.4 m away. If the two slits are separated by 0.28 mm, calculate the least distance from the central bright maximum where the bright fringes of the two wavelengths coincide. OR (a) How does an unpolarized light incident on a Polaroid get polarized? Described briefly, with help of a necessary diagram, the polarization of light by reflection from a transparent medium. (b)Two Polaroid’s ‘A’ and ‘B’ are kept in crossed position. How should a third Polaroid ‘C’ be placed between them so that the intensity of polarized light transmitted by Polaroid B reduces to 1/8th of the intensity of unpolarized light incident on A? |
Q. (a) Describe briefly, with the help of a diagram, the role of the two important processes involved in the formation of a p-n junction. (b)Name the device which is used as a voltage regulator. Draw the necessary circuit diagram and explain its working. OR (a) Explain briefly the principle on which a transistor-amplifier works an a oscillator. Draw the necessary circuit diagram and explain its working. |
Q. (a)Write the expression for the force, F, acting on a charged particle of charge ‘q’, moving with a velocity v in the presence of both electric field E and magnetic field B. Obtain the condition under which the particle moves undeflected through the fields. OR (a) Explain, giving reasons, the basic difference in converting a galvanometer into (i) a voltmeter and (ii) an ammeter. (b)Two long straight parallel conductors carrying steady currents I_{1} and I_{2} are separated by a distance ‘d’. Explain briefly, with the help of a suitable diagram, how the magnetic field due to one conductor acts on the other. Hence deduce the expression for the force acting between the two conductors. Mention the nature of this force. |
CBSE Class 12 Physics Board Exam 2011: Long Answer Type Questions (5 Marks) |
Q. (a) State the principle of the working of a moving coil galvanometer, giving its labeled diagram. (b) "Increasing the current sensitivity of a galvanometer may not necessarily increase its voltage sensitivity." Justify this statement. (c) Outline the necessary steps to convert a galvanometer of resistance RG into an ammeter of a given range. OR (a) Using Ampere's circuital law, obtain the expression for the magnetic field due to a long solenoid at a point inside the solenoid on its axis. (b) In what respect is a toroid different from a solenoid? Draw and compare the pattern of the magnetic field lines in the two cases. (c) How is the magnetic field inside a given solenoid made strong? |
Q. State the working of AC generator with the help of a labeled diagram. The coil of an a.c. generator having N turns, each of area A, is rotated with a constant angular velocity ω. Deduce the expression for the alternating EMF generated in the coil. What is the source of energy generation in this device? OR (a) Show that in an AC circuit containing a pure inductor, the voltage is ahead of current by p/2 in phases. (b) A horizontal straight wire of length L extending from east to west is falling with speed v at right angles to the horizontal component of Earth's magnetic field B. (i) Write the expression for the instantaneous value of the EMF induced in the wire. (ii) What is the direction of the EMF? (iii) Which end of the wire is at the higher potential? |
State the importance of coherent sources in the phenomenon of interference. In Young's double slit experiment to produce interference pattern, obtain the conditions for constructive and destructive interference. Hence deduce the expression for the fringe width. How does the fringe width get affected, if the entire experimental apparatus of Young is immersed in water? OR (a) State Huygens Principle. Using this principle explain how a diffraction pattern is obtained on a screen due to a narrow slit on which a narrow beam coming from a monochromatic source of light is incident normally. (b) Show that the angular width of the first diffraction fringe is half of that of the central fringe. (c) If a monochromatic source of light is replaced by white light, what change would you observe in the diffraction pattern? |
CBSE Class 12th Solved Previous Years' Papers (Last 5+ 1 years') PCM - eBook