SPECTRUM CLASSES
Full Syllabus Test No.2
Class XII Physics
Time 3 HRS MAX MARK 70
General Instructions:
1. All questions are compulsory. There are 27 questions in all.
2. This question paper has four sections: Section A, Section B, Section C and Section D.
3. Section A contains five questions of one mark each, Section B contains seven questions of two marks each, Section C contains twelve questions of three marks each, and Section D contains three questions of five marks each.
4. There is no overall choice. However, internal choices have been provided in two questions of one mark, two questions of two marks, four questions of three marks and three questions of five marks weightage. You have to attempt only one of the choices in such questions
Q.1 Draw graphs showing variation of photoelectric current with applied voltage for two incident radiations of equal frequency and different intensities. Mark the graph for the radiation of higher intensity.
Q.2 Nichrome and copper wires of same length and same radius are connected in series. Current I is passed through them. Which wire gets heated up more ? Justify your answer.
Q.3 Name the phenomenon which shows the quantum nature of electromagnetic radiation.
OR
Define Potential Gradient with its unit . Is it a scalar or a vector quantity ?
Q.4Find the condition under which the charged particles moving with different speeds in the presence of electric and magnetic field vectors can be used to select charged particles of a particular speed.
OR
Draw the intensity pattern for single slit diffraction and double slit interference. Hence, state two differences between interference and diffraction patterns.
Q.5 Write two properties of a material suitable for making (a) a permanent magnet, and (b) an electromagnet.
Q.6 What is the effect on focal length of a lens when dipped in water ?
Q.7 Unpolarised light is passed through a polaroid P1. When this polarized beam passes through another polaroid P2 and if the pass axis of P2 makes angle ϴ with the pass axis of P1, then write the expression for the polarised beam passing through P2. Draw a plot showing the variation of
intensity when ϴ varies from 0 to 2
OR
Draw a circuit diagram of a meter bridge used to determine the unknown resistance R of a given wire. Hence derive the expression for R in terms of the known resistance S.
Q.8 (a) Monochromatic light of wavelength 589 nm is incident from air on a water surface. If µ for water is 1·33, find the wavelength, frequency and speed of the refracted light.
(b) A double convex lens is made of a glass of refractive index 1·55,with both faces of the same radius of curvature. Find the radius of curvature required, if the focal length is 20 cm.
Q.9 Define potential barrier and Depletion layer , How the resistance of PN junction diode changes in forward and reverse Bias.
Q.10 Explain Ampere Maxwell Circuital law ?
Q.11 Write the characteristics of em waves? Write the expression for velocity of electromagnetic waves in terms of permittivity and permeability of the
medium?
Q.12 Define mutual inductance between a pair of coils. Derive an expression for the mutual inductance of two long coaxial solenoids of same length wound one over the other.
OR
Define self-inductance of a coil. Obtain the expression for the energy stored in an inductor L connected across a source of emf.
Q.13 What is the effect on Q , U , V And C When a dielectric medium is completely filled in a PPC when voltage is connected or disconnected.
Q.14 Explain giving reasons for the following :
(a) Photoelectric current in a photocell increases with the increase in the intensity of the incident radiation.
(b) The stopping potential (V0) varies linearly with the frequency (v) of the incident radiation for a given photosensitive surface with the slope remaining the same for different surfaces.
(c) Maximum kinetic energy of the photoelectrons is independent of the intensity of incident radiation.
Q.15 (a) Draw a ray diagram to show the image formation by a combination of two thin convex lenses in contact. Obtain the expression for the power of this combination in terms of the focal lengths of the lenses.
(b) A ray of light passing from air through an equilateral glass prism undergoes minimum deviation when the angle of incidence is 3/4th of the angle of prism. Calculate the speed of light in the prism.
Q.16 (a) Derive an expression for the electric field E due to a dipole of length ‘2a’ at a point distant r from the centre of the dipole on the axial line.
(b) Draw a graph of E versus r for r >> a.
(c) If this dipole were kept in a uniform external electric field E0, diagrammatically represent the position of the dipole in stable and unstable equilibrium and write the expressions for the torque
acting on the dipole in both the cases.
Q.17 How do position of null point in potentiometer changes with(i) increase in length of potentiometer wire(ii)increase in current in primary circuit. Give two reasons for one sided deflection in potentiometer.
Q.18 A particle of mass ‘m’ and charge ‘q’ moving with speed ‘v’ , normal to a uniform magnetic field ‘B’ describes a circular path of radius ‘r’. Derive expressions for the (i) time period of revolution and (ii) kinetic energy of the particle.
Q.19 Two identical loops P and Q each of radius 5 cm are lying in perpendicular planes such that they have a common centre as shown in the figure. Find the magnitude and direction of the net magnetic field at the common centre of the two coils, if they carry currents equal to 3 A and 4 A respectively.
Q.20 The figure shows input waveforms A and B to a logic gate. Draw the output waveform for an OR gate , NAND gate and XOR gate . Write the truth table for this logic gate and draw its logic symbol.
Q.21An aeroplane is flying horizontally from west to east with a velocity of 900 km/hour. Calculate the potential difference developed between the ends of its wings having a span of 20 m. The horizontal component of the Earth’s magnetic field is 5 ´ 10–4 T and the angle of dip is 30°
Q.22 (a) State Bohr’s postulate to define stable orbits in hydrogen atom. How does de Broglie’s hypothesis explain the stability of these orbits ?
(b) A hydrogen atom initially in the ground state absorbs a photon which excites it to the n = 4 level. Estimate the frequency of the photon.
Q.23 (a) Explain the processes of nuclear fission and nuclear fusion by using the plot of binding energy per nucleon (BE/A) versus the mass number A.
(b) A radioactive isotope has a half-life of 10 years. How long will it take for the activity to reduce to 3·125% ?
Q.24(a) A student wants to use two p-n junction diodes to convert alternating current into direct current. Draw the labelled circuit diagram she would use and explain how it works.
(b) Give the truth table and circuit symbol for NAND gate.
Q.25Explain working of PNP transistor as an Amplifier
OR
(a) Explain Working of NPN transistor in Common emitter mode
(b) Draw input and output Characterstic Curve
Q.26(a) State the principle of an ac generator and explain its working with the help of a labelled diagram. Obtain the expression for the emf induced in a coil having N turns each of cross-sectional area A, rotating with a constant angular speed ‘ω’ in a magnetic field B directed perpendicular to the axis of rotation.
(b) An aeroplane is flying horizontally from west to east with a velocity of 900 km/hour. Calculate the potential difference developed between the ends of its wings having a span of 20 m. The horizontal component of the Earth’s magnetic field is 5x10–4T and the angle of dip is 30°.
OR
A device X is connected across an ac source of voltage V = V0sin ωt. The current through X is given as I = I0 sin(ωt + /2)
(a) Identify the device X and write the expression for its reactance.
(b) Draw graphs showing variation of voltage and current with time over one cycle of ac, for X.
(c) How does the reactance of the device X vary with frequency of the ac ? Show this variation graphically.
(d) Draw the phasor diagram for the device X.
Q.27 (a)Derive expression for magnifying power of Compound microscope with ray diagram . (b) A small telescope has an objective lens of focal length 144 cm and an eye-piece of focal length 6.0 cm. What is the magnifying power of the telescope? What is the separation between the objective and the eye-piece?
OR
(a) Define a wavefront. Using Huygens’ principle, verify the laws of reflection at a plane surface.
(b) In a single slit diffraction experiment, the width of the slit is made double the original width. How does this affect the size and intensity of the central diffraction band ? Explain.
(c) When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the obstacle. Explain why
PHYSICS By Er.Shyam Pachori CL 157 D.D Nagar Mob.:9039803981
