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ISC Class XII Sample / Model Paper 2026 : Physics

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Amirth Royin
St. Francis School (SFS), Palayur, Chavakkad, Thrissur
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KARNATAKA ICSE SCHOOLS ASSOCIATION ISC STD. XII Preparatory Examination 2026 Subject Physics Date: 15.01.2026 Maximum Marks : 70 Time Allowed : Three Hours (Candidates are allowed an additional 15 minutes for only reading the paper. They must not start writing during this time ) This paper is divided into four sections - A,B,C and D. Answer all questions. Section A consists of one question having sub- parts of one mark each. Section B consists of seven questions of two marks each. Section C consists of nine question of three marks each,and Section D consists of three questions of five marks each. Internal choices have been provided in one questions each in section B, Section C and section D. The intended marks for questions are given in brackets[ ]. SECTION A [14 MARKS] QUESTION 1 (A) Question (i) to (vii) below choose the correct alternative (a) (b) (c) (d) for each of the questions given below (i) A sphere encloses an electric dipole with charge 3* 106C. What is the total electric flux across the sphere? a) -3*10-6 N-m2/C b) Zero c) 3*10-6 N-m2 C d) 6*10-6 N-m2C (ii)Two long parallel wires are at a distance of 1m. Both of them carry 1A of current. The force of attraction per unit length between the two wires is (a)2 *10-7 N/m (b)2 *10-8 N/m (c)5 *10-8 N/m (d)10-7N/m (iii) The magnetic susceptibility is negative for (iv) a. Paramagnetic material only b. Ferromagnetic material only c. Paramagnetic and ferromagnetic materials d. Diamagnetic material only A proton and an -particle are accelerated from rest to the same energy. The de-Broglie wavelengths p and are in the ratio a. 2:1 b. 1:1 c. :1 Page 1 of 9 d.4:1 (v)Which one of the following represents forward bias diode? a. b. c. d. (vi) Minimum deviation occurs in a prism when: a. Angle of incidence is zero b. Angle of incidence equals angle of emergence c. The ray grazes the base d. The prism is equilateral (vii) Assertion (A): The focal length of a convex lens decreases when it is placed in water. Reason (R): The refractive index contrast between the lens material and surrounding medium decreases in water. a. Both Assertion and Reason are true and Reason is the correct explanation for Assertion. b. Both Assertion and Reason are true but Reason is not the correct explanation for Assertion. c. Assertion is true and Reason is false. d. Assertion is false and Reason is true [B] Answer the following question briefly: (i) In an industrial furnace, the resistance of a metal heating element is measured as temperature increases. Plot the graph of resistance (R) versus temperature (T) for the metal.? [1] (ii) State one way to reduce energy loss in a transformer. [1] (iii)Give one difference between refracting and reflecting type telescope. [1] (iv) In an experiment of photo electric effect , following graph were obtained between the photo current (I) and the anode potential (V) . Name the characteristics of the incident radiation that was kept constant in this experiment. [1] (v) What is the main difference between fission and fusion? [1] (vi) Name one device that works on the principle of total internal reflection. [1] (vii) Which type of biasing is required for an LED to emit light? [1] Page 2 of 9 SECTION B- [14 MARKS] QUESTION 2 Three capacitor C1, C2 and C3 of capacitance 6uf each are connected to a 12 V battery as shown find the equivalent capacitor of the network OR V-I graphs for parallel and series combination of two metallic resistors are as shown in figure. Which graph represents parallel combination ? Justify your answer. QUESTION 3. At a far away distance r along the axis from an electric dipole electric field is E. Find the electric field at distance 2r along the perpendicular bisector. [2] QUESTION 4. [2] Using the circuit shown (a cell of emf E and internal resistance r connected in series with an external resistor R), derive an expression for the internal resistance of the cell in terms of measurable quantities. OR Page 3 of 9 Following circuit was set up in a meter bridge experiment to determine the value of X of an unknown resistance (a) Write the formula to be used for finding X from the observations. (b) If the resistance R is increased , what will happen to balancing length . QUESTION 5. [2] (i) An equiconvex lens has a power P. It is cut into two equal symmetrical halves along a plane containing the principal axis.Determine the power of one half of the lens. Explain your reasoning. (ii) A convex lens has power +5 D in air. It is now immersed in water. Will its power increase, decrease, or remain the same? QUESTION 6. [2] A galvanometer is converted into a voltmeter of range (0 V) volt by using a series resistance of 8800 . If a series resistance of 4200 is used instead, the voltmeter range becomes half, i.e. (0 V/2) volt. Calculate the resistance of the galvanometer, QUESTION 7. [2] Name the constituent radiation of electromagnetic spectrum which (a) Is used for studying crystal structure (b) For taking photographs of the sky during night and foggy conditions? QUESTION 8. [2] With reference to the photoelectric effect, define the term (a) Work function (b) Threshold wavelength for a given metal Page 4 of 9 SECTION -C [ 27 MARKS] QUESTION 9. [3] Derive an expression for the electric field at any point on the equatorial line of an electric dipole. QUESTION 10. [3] A parallel-plate capacitor has plate area A and separation d, with air between the plates. An insulating dielectric slab of the same plate area but thickness d/2 and dielectric constant K = 4 is inserted between the plates as shown in the figure. Find the ratio of the new capacitance to the original capacitance. OR The figure shows a circuit with three ideal batteries. Find the magnitude of current AG, BF and CD. QUESTION 11. Apply Biot savart law to derive an expression for the magnetic field at the centre of a current carrying circular loop. [3] QUESTION 12. An electron of mass m=9.1 10 [3] 31 kg and charge e=1.6 10 19 7 C moves with a velocity of 6 10 m/s along the X-axis. It enters a region where a uniform magnetic field of strength B=2 10 3 T is directed along the Zaxis. (a) Draw a diagram showing the velocity vector, magnetic field, and the direction of the resulting force on the electron. (b) Calculate the radius of the circular path described by the electron OR Page 5 of 9 Two long straight wires are held perpendicular to the plane of the paper and are 5 m apart. The wires carry currents of 2.5 A and 5 A in the same direction (See Figure given below). Calculate the magnitude of the net magnetic field at the midpoint. QUESTION 13. [3] In the diagram, a group of parallel rays is incident on a convex lens and converges to point b after refraction (a) What type of wavefront corresponds to the parallel rays approaching the lens? (b) Draw and label the wave front formed at point b after the rays pass through the lens. (c) What is a wavefront? QUESTION 14. [3] A teacher demonstrates Young s Double Slit Experiment using two very closely spaced slits. She then adjusts the experimental setup by decreasing the distance between the slits while keeping all other parameters the same. a) What will be the effect on the fringe width when the slit separation is decreased? b) Explain using the relationship between fringe width and slit separation. c) How does the visibility of fringes change due to this adjustment? QUESTION 15. [3] A plane wavefront approaches the boundary between two transparent media, entering the denser medium at an oblique angle. (a) Using a neat and labelled diagram, illustrate how the wavefront changes direction at the interface. Show the incident wavefront, refracted wavefront, angle of incidence, and angle of refraction. Page 6 of 9 (b) Applying Huygens principle to the refraction of wave fronts at this boundary, derive the mathematical relationship between the velocities of light in the two media and hence obtain Snell s law of refraction. QUESTION 16. [3] A biology student observes the structure of onion cells using an optical instrument in the laboratory. 1. Name the instrument used by the student. 2. Draw a labelled ray diagram showing how this instrument forms a magnified image when: (a) The object (onion cell slide) is placed just beyond the focal length of the objective lens. (b) The final image is formed at the least distance of distinct vision (25 cm). QUESTION 17. [3] In the study of a photoelectric effect, the graph between the stopping potential V and frequency V of the incident radiation on two different metals P and Q is shown below : (i) Which of the two metals has higher threshold frequency ? (ii) Determine the work function of the metal which has greater value . (iii) Find the maximum kinetic energy of the electron emitted by the light of frequency 8*1014 Hz SECTION - D [15 MARKS] QUESTION 18. [5] The graph shows below, depict the variation of current im Vs. angular frequency w for two different series LCR- circuit. Page 7 of 9 Observe the graph carefully: (i) State the relation between L and C values of the circuit, when the current in the two circuits are maximum. (ii) Calculate the ratio of the power factor of circuit (i) and (ii) (iii)Indicate the circuit for which (a) quality factor is larger (b) maximum resistance Give a reason for each case OR (i) State Faraday s law of electromagnetic induction and mention the utility of Lenz s law. Obtain an expression for self-inductance of a coil in terms of its geometry and permeability of the medium. (ii) A resistance of 20 W, a capacitance of 80 mF and an inductor of 50 mH are connected in series. This combination is connected across a 220 V ac supply of variable frequency. When the frequency of supply equals the natural frequency of the circuit, calculate : (1) angular frequency of supply (2) impedance of the circuit QUESTION 19. [5] (i) Derive an expression for the energy of electron in nth orbit in Bohr s model of hydrogen atom. (ii) Calculate binding energy per nucleon (in MeV) of 12C6 Given : m (12C6 ) = 12.000000 u m ( 1N0) = 1.008665 u m ( 1H1) = 1.007825 u OR ii) Figure shows the energy level diagram of hydrogen atom (i) Find out the transition which results in the emission of a photon of wavelength 496nm (ii) Which transition corresponds to the emission of radiation of maximum wavelength? Justify your answer. Page 8 of 9 (iii) According to Bohr s theory of hydrogen atom, calculate angular momentum of the electron in 3rd Bohr orbit. (b) What is the role of the moderator and control rods in a nuclear reactor? QUESTION 20. [5] When a p-type and n-type semiconductors are joined, electrons from the n-region and holes from the pregion diffuse across the junction. This forms a depletion region, which contains immobile ions and acts as a barrier to charge carrier flow. The width of the depletion region depends on the bias applied: it narrows in forward bias and widens in reverse bias. LEDs (Light Emitting Diodes) work on the principle of electron hole recombination. When an LED is forward biased, electrons cross the reduced depletion region and recombines with holes. This recombination releases energy equal to the energy band gap (Eg) of the LED material. The color of light produced depends on Eg higher band gap materials emit shorter-wavelength (higher-energy) light. A lab tests three LEDs made from different semiconductor materials. Their wavelengths are: LED Wavelength (nm) X 420 nm Y 560 nm Z 650 nm The depletion region width in each LED is measured before and after forward bias. 1. Which LED has the highest energy band gap and which has the lowest, based on the wavelengths given? 2. Explain why the depletion region becomes narrower when the LED is forward biased. 3. Draw a labelled diagram of a half wave rectifier. Show graphically how its output voltage varies with time. ************************* Useful Constants & Relations: 1 Permittivity of vacuum 0: 2 Constant for Coulomb s law (1/4 0): 9 109 m/F 3 Constant in Magnetism ( 0/4 ): 1 10-7H/m 4 Elementary charge e: 1.6 X 10-19C 5 Mass of an electron m: 9 x 10-31kg 8 85 10-12F/m Page 9 of 9

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