Depict the direction of the magnetic field lines due to a circular current carrying loop? • How would a biconvex lens appear when placed in a trough of liquid having the same refractive index as that of the lens? • What is the difference between an n-type and an p-type intrinsic semiconductor? • Define ‘intensity’ of radiation in photon picture of light?
5. Why is the classical (Rutherford) model for an atom – of electron orbitting around the nucleus – not able to explain the atomic structure? • 6. What is the function of a repeater used in communication system? • 7. Distinguish between a dielectric and a conductor? • 8. When an ac source is connected across an ideal inductor, show on a graph the nature of variation of the voltage and the current over one complete cycle?
9. A battery of emf 10 V and internal resistance 3 Ω is connected to a resistor. If the current in the circuit is 0.5 A, find • The resistance of the resistor. • The terminal voltage of the battery. • 10. A carrier wave of peak voltage 12 V is used to transmit a message signal. Calculate the peak voltage of the modulating signal in order to have a modulation index of 75%.
11. A proton and a deuteron, each moving with • velocity enter simultaneously in the region on • magnetic field B acting normal to the direction of • velocity. Trace their trajectories establishing the • relationship between the two. • 12. A lamp is connected in series with a capacitor. • Predict your observation when this combination • is connected in turn across • ac source and • a dc battery. What change would you notice in • each case if the capacitance of capacitor is • increased?
13. (a) Identify the boxes, ‘P’ and ‘Q’ in the block diagram of a receiver shown in the figure. (b) Write the function of the blocks ‘P’ and ‘Q’
14. Determine the potential difference across the plates of the capacitor ‘C ’ of the network shown in the figure. [ Assume E2 > E1 ] 15. A particle of mass 10-3 kg and charges 5 μC enters into a uniform electric field of 2 X 105 NC-1, moving with a velocity of 20 ms-1 in a direction opposite to that of the field. Calculate the distance it would travel before coming to rest. 1 2
16. (a) How does a diamagnetic material behave when it is cooled to very low temperatures? (b) why does a paramagnetic sample display greater magnetisation when cooled? Explain. 17. State two conditions required for obtaining coherent sources? In young’s arrangement to produce interference pattern, show that dark and bright fringes appearing on the screen are equally spaced .
18. (a) Plane and convex mirrors are known to produce virtual image of the objects. Draw a ray diagram to show how, in the case of convex mirrors, virtual objects can produce real images. (b) Why are convex mirrors used as side view mirrors in vehicles? (or)
A fish in a water tank sees the outside world as if it ( the fish) is at the vertex of a cone such that the circular base of the cone coincides with the surface of water . Given the depth of water, Where fish is located. Being ‘h’ and the critical angle for water-air interface being ‘ ic’find out by drawing a suitable ray diagram the relationship between the radius of the cone and the height ‘h ’ .
19. Two identical coils, each of radius ‘R’ and number of turns ‘N’ are lying in perpendicular planes such that their centres coincide. Find the magnitude and direction of the resultant magnetic field at the centre of the coils, if they are carrying currents ‘I’and ‘ I’ respectively. 20. Explain briefly, giving a suitable diagram, how an unpolarised light incident on the interface separating two transparent media gets polarised on reflection. Deduce the necessary condition for it.
21. Draw a ray diagram to show the formation of the image of an object placed on the axis of a convex refracting surface, of radius of curvature ‘R’, separating the two media of refractive indices ‘n1’ and ‘n2’ (n2 > n1) . Use this diagram to deduce the relation - = , where u and v represent respectively the distance of the object and the image formed.
22. (a) How does an oscillating charge produce electromagnetic wave? Explain. (b) Draw a sketch showing the propagation of a plane e.m. wave along the Z direction, clearly depicting the directions of oscillating electric and magnetic field vectors.
23. Answer the following : (i) Do the frequency and wavelength change when light passes from a rarer to a denser medium? (ii) Why is the value of the angle of deviation for a ray of light undergoing refraction through a glass prism different for different colours of light? (iii) In a single slit diffraction experiment, the width of the slit is reduced to half its original width. How would this affect the size and intensity of the central maximum?
24. State Gauss’s law. A thin straight infinitely long conducting wire of linear charge density ‘λ’ is enclosed by a cylindrical surface of radius ‘r’ and length ‘l’ – its axis coinciding with the length of the wire. Obtain the expression for the electric field, indicating its direction, at a point on the surface of the cylinder. or An electric dipole is kept in a uniform electric field. Derive an expression for the net torque acting on it and write its direction. State the conditions under which the dipole is in (i) stable and (ii) unstable equilibrium
25. Draw the transfer characteristic of a base biased transistor in CE configuration. Mark the regions where the transistor can be used as a switch. Explain briefly its working. 26. Write Einstein’s photoelectric equation, giving the main points of the photon picture of electromagnetic radiation on which this equation is based. State three observed features of photoelectric effect which can be photoelectric effect which can be explained by Einstein’s equation.
27. The figure shows the V – I characteristics of a semiconductor device. Identify this device. Explain briefly, using the necessary circuit diagram, how this device is used as a voltage regulator
28. (a) Derive the relation between current density and potential difference ‘V’ across a current carrying conductor of length ‘l’ area of cross- section ‘A’ and the number density ‘n’ of free electrons. (b) Estimate the average drift speed of conduction electrons in a copper wire of cross- sectional area1.0 X 10-7 m2 carrying a current of 1.5 A. [Assume that the number density of conduction electrons is 9 x 1028 m-3] (or)
Use Kirchhoff’s rules to obtain the balance condition in a Wheatstone bridge. Calculate the value of R in the balance condition of the Wheatstone bridge, if the carbon resistor connected across the arm CD has the colour sequence red, red and orange, as is shown in the figure. If now the resistances of the arm BC and CD are interchanged, to obtain the balance condition, another carbon resistor is connected in place of R. What would now be the sequence of colour bands of the carbon resistor?
29. (a) Using Bohr’s theory of hydrogen atom, derive the expression for the total energy of the electron in the stationery states of the atom. (b) If electron in the atom is replaced by a particle (muon) having the same charge but mass about 200 times as that of the electron to form a muonic atom, how would (i) the radius and (ii) the ground state energy of this affected? (c) Calculate the wavelength of the first spectral line in the corresponding Lyman series of this atom. (or)
Define the term ‘activity’ of a given sample of radionuclide. Write the expression for the law of radioactive decay in terms of the activity of a given sample. • A radioactive isotope has a half life of T years. How long will it take the activity to reduce to 3.125% of its original value? • When a nucleus (X) undergoes β-decay, the transforms to the nucleus (Y), does the pair (X, Y) form isotopes, isobars or isotones? Justify your answer.
30. (a) A voltage V = V2 sin ωt applied to a series LCR circuit drives a current i = i2 sin ωt in the circuit. Deduce the expression for the average power dissipated in the circuit. (b) For circuits used for transporting electric power, a low power factor implies large power loss in transmission. Explain (c) Define the term ‘wattles current’. (or)
(a) Starting from the expression for the Lorentz magnetic force acting on the free charge carriers of a conductor moving in a perpendicular magnetic field, obtain the expression for the motional emf induced. (b) Hence deduce the expression for the power delivered by the source and the power dissipated as Joule heat. (c) A straight wire extending from east to west falls with a speed v at right angles to the horizontal components of the Earth’s magnetic field. Which end of the wire would be at the higher electrical potential and why?