Physics sample paper, Exams of Physics

Download Physics sample paper and more Exams Physics in PDF only on Docsity! Class: XII SESSION : 2022-2023 CBSE SAMPLE QUESTION PAPER (THEORY) SUBJECT: PHYSICS Maximum Marks: 70 Marks Time Allowed: 3 hours. General Instructions: (1) There are 35 questions in all. All questions are compulsory (2) This question paper has five sections: Section A, Section B, Section C, Section D and Section E. All the sections are compulsory. (3) Section A contains eighteen MCQ of 1 mark each, Section B contains seven questions of two marks each, Section C contains five questions of three marks each, section D contains three long questions of five marks each and Section E contains two case study based questions of 4 marks each. (4) There is no overall choice. However, an internal choice has been provided in section B, C, D and E. You have to attempt only one of the choices in such questions. 5. Use of calculators is not allowed. SECTION A Q. NO. MARKS 1 According to Coulomb's law, which is the correct relation for the following figure? (i) q1 q2> 0 (ii) q1 q2<0 (iii) q1 q2 =0 (iv) 1> q1/ q2 > 0 1 2 The electric potential on the axis of an electric dipole at a distance ‘r from it’s centre is V. Then the potential at a point at the same distance on its equatorial line will be (i) 2V (ii) -V (iii) V/2 (iv) Zero 1 3 The temperature (T) dependence of resistivity of materials A and material B is represented by fig (i) and fig (ii) respectively. Identify material A and material B. (i) material A is copper and material B is germanium (ii) material A is germanium and material B is copper (iii) material A is nichrome and material B is germanium (iv) material A is copper and material B is nichrome 1 4 Two concentric and coplanar circular loops P and Q have their radii in the ratio 2:3. Loop Q carries a current 9 A in the anticlockwise direction. For the magnetic field to be zero at the common centre, loop P must carry (i) 3A in clockwise direction (ii) 9A in clockwise direction (iii) 6 A in anti-clockwise direction (iv) 6 A in the clockwise direction. 1 5 A long straight wire of circular cross section of radius a carries a steady current I. The current is uniformly distributed across its cross section. The ratio of the magnitudes of magnetic field at a point distant a/2 above the surface of wire to that at a point distant a/2 below its surface is (i) 4 :1 (ii) 1:1 (iii) 4: 3 (iv) 3 :4 1 6 If the magnetizing field on a ferromagnetic material is increased, its permeability (i) decreases (ii) increases (iii) remains unchanged (iv) first decreases and then increases 1 (i) 30 V (ii) 58 V (iii) 29 V (iv) 15 V 15 The electric potential V as a function of distance X is shown in the figure. The graph of the magnitude of electric field intensity E as a function of X is 1 (i) (ii) (iii) (iv) 16 Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. a) Both A and R are true and R is the correct explanation of A b) Both A and R are true and R is NOT the correct explanation of A 1 c) A is true but R is false d) A is false and R is also false ASSERTION(A): The electrical conductivity of a semiconductor increases on doping. REASON: Doping always increases the number of electrons in the semiconductor. 17 Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. a) Both A and R are true and R is the correct explanation of A b) Both A and R are true and R is NOT the correct explanation of A c) A is true but R is false d) A is false and R is also false ASSERTION: In an interference pattern observed in Young's double slit experiment, if the separation (d) between coherent sources as well as the distance (D) of the screen from the coherent sources both are reduced to 1/3rd, then new fringe width remains the same. REASON: Fringe width is proportional to (d/D). 1 18 Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. a) Both A and R are true and R is the correct explanation of A b Both A and R are true and R is NOT the correct explanation of A c) A is true but R is false d) A is false and R is also false Assertion(A) : The photoelectrons produced by a monochromatic light beam incident on a metal surface have a spread in their kinetic energies. Reason(R) : 1 The energy of electrons emitted from inside the metal surface, is lost in collision with the other atoms in the metal. SECTION B 19 Electromagnetic waves with wavelength (i) λ1 is suitable for radar systems used in aircraft navigation. (ii) λ2 is used to kill germs in water purifiers. (iii) λ3 is used to improve visibility in runways during fog and mist conditions. Identify and name the part of the electromagnetic spectrum to which these radiations belong.Also arrange these wavelengths in ascending order of their magnitude. 2 20 A uniform magnetic field gets modified as shown in figure when two specimens A and B are placed in it. (i)Identify the specimen A and B. (ii) How is the magnetic susceptibility of specimen A different from that of specimen B? 2 21 What is the nuclear radius of 125Fe ,if that of 27 Al is 3.6 fermi?. OR The short wavelength limit for the Lyman series of the hydrogen spectrum is 913.4 A0. Calculate the short wavelength limit for the Balmer series of the hydrogen spectrum. 2 22 A biconvex lens made of a transparent material of refractive index 1.25 is immersed in water of refractive index 1.33. Will the lens behave as a converging or a diverging lens? Justify your answer. 2 Surface C: photo emission occurs and photoelectrons have some kinetic energy. Using Einstein’s photo-electric equation, explain the three observations. OR The graph shows the variation of photocurrent for a photosensitive metal (a)What does X and A on the horizontal axis represent? (b)Draw this graph for three different values of frequencies of incident radiation ʋ1, ʋ 2 and ʋ 3 (ʋ 3>ʋ 2>ʋ1) for the same intensity. (c) Draw this graph for three different values of intensities of incident radiation I1, I2 and I3 (I3> I2>I1) having the same frequency. 30 The ground state energy of hydrogen atom is -13.6 eV. The photon emitted during the transition of electron from n=3 to n=1 state, is incident on a photosensitive material of unknown work function .The photoelectrons are emitted from the material with the maximum kinetic energy of 9eV.Calculate the threshold wavelength of the material used. 3 SECTION D 31 (a)Draw equipotential surfaces for (i)an electric dipole and (ii) two identical positive charges placed near each other. (b) In a parallel plate capacitor with air between the plates, each plate has an area of 6 x 10-3m2 and the separation between the plates is 3 mm. (i) Calculate the capacitance of the capacitor. (ii) If the capacitor is connected to 100V supply, what would be the the charge on each plate? (iii) How would charge on the plate be affected if a 3 mm thick mica sheet of k=6 is inserted between the plates while the voltage supply remains connected ?. 5 OR (a)Three charges –q, Q and –q are placed at equal distances on a straight line. If the potential energy of the system of these charges is zero, then what is the ratio Q:q? (b)(i) Obtain the expression for the electric field intensity due to a uniformly charged spherical shell of radius R at a point distant r from the centre of the shell outside it. (ii) Draw a graph showing the variation of electric field intensity E with r, for r > R and r < R. 32 (a) Explain the term drift velocity of electrons in a conductor .Hence obtain the expression for the current through a conductor in terms of drift velocity. (b) Two cells of emfs E1 and E2 and internal resistances 𝑟 and 𝑟 respectively are connected in parallel as shown in the figure. Deduce the expression for the (i) equivalent emf of the combination (ii) equivalent internal resistance of the combination (iii) potential difference between the points A and B. OR (a) State the two Kirchhoff’s rules used in the analysis of electric circuits and explain them. (b) Derive the equation of the balanced state in a Wheatstone bridge using Kirchhoff’s laws. 5 33 a) Draw the graph showing intensity distribution of fringes with phase angle due to diffraction through a single slit. What is the width of the central maximum in comparison to that of a secondary maximum? b) A ray PQ is incident normally on the face AB of a 5 triangular prism of refracting angle 600 as shown in figure. The prism is made of a transparent material of refractive index √ . Trace the path of the ray as it passes through the prism. Calculate the angle of emergence and the angle of deviation. OR a) Write two points of difference between an interference pattern and a diffraction pattern. b) (i) A ray of light incident on face AB of an equilateral glass prism, shows minimum deviation of 30°. Calculate the speed of light through the prism. (ii) Find the angle of incidence at face AB so that the emergent ray grazes along the face AC. SECTION E