
	Trending ▼ ICSE CBSE 10th ISC CBSE 12th CTET GATE UGC NET Vestibulares ResFinder

ISC Class XII Prelims 2026 : Physics (St. Michael's Academy (SMA), Chennai)

9 pages, 51 questions, 0 questions with responses, 0 total responses,

	Tech Sharan Chennai	+Fave Message
	Profile Timeline Uploads

Home > mageswari > F Also featured on: School Page

Formatting page ...

STD: XII ST. MICHAELS ACADEMY 9-1-26 REVISION-1 EXAMINATION - JAN 2026 MARKS:70 TIME:3HRS General Instructions: You are allowed an additional 1 5 minutes for only reading the question paper. You must NOT start writing during reading time. This question paper has 20 questions. The paper has four sections: A, B, C and D. Internal choices have been provided in two questions each in Sections B, C and D. Section A consists of one question having fourteen sub-parts of one mark each. Section B consists of seven questions of two marks each. Section C consists of nine questions of three marks each. Section D consists of three questions of five marks each. Answer all questions. The intended marks for questions are given in brackets []. A list of useful constants and relations is given at the end of this paper. A simple scientific calculator without a programmable memory may be used for calculations. Section A[ 14 marks] Answer the following questions: A) In questions (i) to (vii) below, choose the correct alternative (a), (b), (c) or (d) for each of the questions given below: [7] (i) In the Wheatstone bridge circuit shown below, P = 10 , Q = 20 R = 200 and S = 100 , emf of the battery being 2 V. The current flowing through the galvanometer is (ii) a) 1A b) 3A c) 0 d) 2A A magnetic dipole moment is a vector quantity directed from a) East to west direction b) west to east direction c) south to north pole d) north to south pole (iii) A generator produces a voltage given by V= 240 sin 120t , where t is in seconds. The frequency and rms voltage are a) 60Hz,120V b) 120Hz,60V c) 19Hz, 240/ 2 V d) 19Hz, 240/ 3 (iv) The relative permeability of substance X is slightly less than one and that of substance Y is slightly more than one. Then, a) b) c) d) X is paramagnetic and Y is ferromagnetic X is diamagnetic and Y is ferromagnetic X is paramagnetic and Y is diamagnetic X is diamagnetic and Y is paramagnetic (v) If the kinetic energy of moving electrons is made four times, then their de-Broglie wavelength becomes a) eight times b) four times c) two times d) half (vi) If the amplitude ratio of two sources producing interference is 3:5, then the ratio of intensities at maxima and minima is a) 25:16 b) 5:3 c) 16:1 d) 25:9 (vii) Given below are the two statements marked, Assertion and reason. Read the two statements and choose the correct option. Assertion: Diffraction of light is difficult to observe in everyday situations but can be observed in laboratory conditions. Reason: To produce diffraction of waves, size of the obstacle must be comparable to the wavelength of the waves. 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) Both Assertion and Reason are false. B. Answer the following questions briefly: [7] (i) What is the source of electromagnetic waves? (ii) Draw the energy band diagram for a n-type semiconductor. (iii) Figure shows below an ideal transformer. Explain why current flowing through secondary coil is greater than that in primary coil. (output) (iv) (v) What is the minimum energy a gamma ray ( ) photon should possess to produce an electron positron pair? The closed loop PQRS of wire is moved inside a uniform magnetic field at right angles to the plane of paper as shown in the figure. Predict the direction of induced current in the loop. (vi) Define Threshold wavelength. (vii) What will be the effect (if any) on the fringe width in Young s double slit experiment if red light is used in place of violet light? Section B [14 marks] Question 2 (i) [2] Describe how the resistivity of the conductor depends upon (a) Number density n of free electrons and (b) (b) relaxation time (OR) (ii) The figure shows a plot of terminal voltage V versus the current I of a given cell. Calculate from the graph (a) Emf of the cell (b) Internal resistance of the cell Question 3 [2] Two conducting wires X and Y are as shown below: The number density of the electrons in Y is three times that in X. These are joined in series across a battery. Find the ratio of drift speed of electron in two wires. Question 4 (i) [2] If the de-Broglie wavelength of proton and -particles are the same, then what will be the ratio of their speeds? (OR) (ii) The threshold frequency of a metal is f. When the light of frequency 2f is incident on the metal plate, the maximum velocity of photoelectron is v1. When the frequency of the incident radiation is increased to 5f, the maximum velocity of the photoelectrons is v2. Find the ratio of v1: v2. Question 5 [2] A wire of length L is bent round in the form of a coil having N turns of same radius. If a steady current I flows through it in clockwise direction, then find the magnitude and direction of the magnetic field produced at its centre. Question 6 [2] A ray of light moves from vacuum into a medium of refractive index n. If the angle of incidence is twice the angle of refraction, then find the angle of refraction in terms of n. Question 7 (i) (ii) [2] Arrange the electromagnetic waves in increasing order of their frequencies: Visible light, -rays, X-rays, microwaves, radio waves, infrared radiations, and ultraviolet radiations. What is the speed of radio waves in vacuum? Question 8 [2] The radii of curvature of the surfaces of a double convex lens are 20 cm and 40cm respectively and its focal length is 20cm. What is the refractive index of the material of the lens? Section C [21 marks] Question 9 [3] An infinite plane metallic sheet having surface charge density + is placed in vacuum. P is the point at a small distance r to its right. (i) Write an expression for intensity of electric field at point P. (ii) Now, an identical charged sheet having surface charge density - is placed parallel to the first sheet such that the point P is to its left at the same distance r. The point P lies in between the plates. (a) What is the resultant intensity of electric field at point P? (b) What is its direction? Question 10 (i) [3] Calculate the equivalent capacitance of the circuit between points A and B and charge on C1 shown in the figure given below: (OR) (ii) A dielectric slab of dielectric constant K and thickness t is introduced between the two plates of a capacitor of plate separation d(>t) and common area A . (a) Write the expression for the capacitance. (b) If the dielectric slab covers half the distance of separation between the two plates. Calculate the new capacitance. (c) Calculate the capacitance when the whole space between the plates is filled with the dielectric. Question 11 [3] (a) In a uniform electric field E=10N/C, there are 3 points A, B and C. Which one 2m apart from each other as shown in the figure. Find (i) VA-VB and (ii) VB-VC (b) Write one property of an equipotential surface. Question 12 Figure below shows an electric circuit [3] Apply Kirchhoff s laws to calculate current I flowing through the 2ohm resistor and Emf of the cell. (OR) Three identical cells each of emf 2V and internal resistance 1 are connected in series to form a battery. The battery is then connected to a parallel combination of two identical resistors, each of resistance 6 . Find the current delivered by the battery. Question 13 [3] (a) A galvanometer can be converted into a voltmeter of certain range by connecting a resistance of 980 in series with it. When the resistance is 470 connected in series, the range is halved. Find the resistance of the galvanometer. (b) What is the nature of the magnetic field in a moving coil galvanometer? Question 14 [3] (a) A plane wavefront approaches a plane surface separating two media. If medium 1 is optically denser and medium 2 is optically rarer, using Huygens principle explain and show how refracted wavefront is constructed? (b) Verify Snell s law. Question 15 [3] A student while performing the experiment with prism plot the following graph. (i) (ii) (iii) What is the angle of the prism? What is the refractive index of the prism? At which angle the refracted ray parallel to the base of the prism? Question 16 (i) (ii) [3] Draw the circuit diagram of a full wave rectifier. Define the terms depletion region and potential barrier. Question 17 [3] The table below represents the binding energy per nucleon and mass number of a few elements. (i) (ii) (iii) What does the binding energy per nucleon of hydrogen signify? Of Lithium and gold which element has more tightly bound nucleus? Give reason. Which element has the highest mass defect per nucleon among the given element? Section D [15 marks] Question 18 (i) A. An LCR circuit is shown in the figure. It is connected with an AC voltage source of V=100sin500t. Determine: a) impedance b) power factor c) peak value of current d) Q- factor B. Also, define wattless current. [4] [1] (OR) (ii) A. An AC voltage V=Vm sin t is applied across an inductor of inductance L. Find the instantaneous power supplied to the inductor. [2] B. Draw a plot showing the variation of P with t of the AC source used. [1] C. Calculate the impedance in the given AC circuit. [2] Question 19 (i) A. Astronomical telescope may be refracting or reflecting type. Which of the two produce image of better quality? Justify your answer. [1] B. A compound microscope has an objective of focal length 1.25 cm and eyepiece of focal length 5cm. A small object is kept at 2.5cm from the objective. If the final image is formed at infinity, find the distance between the objective and the eye piece. [2] C. An astronomical telescope uses two lenses of powers 10D and 1D. If the image of the distant object is formed at infinity, Calculate the length of the telescope. [1] D. Why should the objective lens of a compound microscope have a small focal length? [1] (OR) (ii) A. A converging and diverging lens of equal focal lengths are placed coaxially in contact. Find the power of the combination. [1] B. A converging lens of refractive index 1.5 is kept in a liquid medium having same refractive index. What will be the focal length of lens in the medium? [1] C. A point object O is kept in a medium of refractive index n1 in front of a convex spherical surface of radius of curvature R which separates the second medium of refractive index n2 from the first one as shown in the figure. Draw the ray diagram showing the image formation and deduce the relation between the object distance and image distance in terms of n1, n2 and R. [3] Question 20 Hydrogen spectrum consists of discrete bright lines in a dark background and it is specifically known as hydrogen emission spectrum. There is one more type of hydrogen spectrum that exists where we get dark lines on the bright background. It is known as absorption spectrum. Balmer found an empirical formula by the observation of a small part of this spectrum. For Lyman series, the emission is from nth state to first state, for Paschen series, it is from nth state to third state. Atoms of different elements essentially have different emission spectrums. Therefore, the emission spectrum of an atom is referred as the finger print of the element. (i) (ii) (iii) (iv) (v) When the electron jumps from the orbit n=2 to n=4, then find the wavelength of the absorbed radiation in terms of Rydberg s constant and in metres. [1] State Bohr s quantization condition for orbiting electron in a hydrogen atom. [1] Write the ratio of radius of first three orbits of hydrogen atom. [1] Find the energy required to remove an electron from the third orbit of hydrogen atom. [1] Name the electromagnetic spectrum in which Balmer series lie? [1] ================================================================

Formatting page ...

mageswari chat

Horizontal lines at:
Guest Horizontal lines at:
AutoRM Data:
Box geometries: