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Model 3 Mark Book Back Questions (New Syllabus) 2020

12th Standard EM

    Reg.No. :


Time : 01:00:00 Hrs
Total Marks : 30

    Part A

    30 x 3 = 90
  1. Calculate the electrostatic force and gravitational force between the proton and the electron in a hydrogen atom. They are separated by a distance of 5.3 × 10-11 m. The magnitude of charges on the electron and proton are 1.6 × 10-19 C. Mass of the electron is me = 9.1 × 10-31 kg and mass of proton is mp = 1.6 × 10-27 kg.

  2. Calculate the electric field due to a dipole on its axial line and equatorial plane.

  3. Obtain the expression for energy stored in the parallel plate capacitor.

  4. A potential difference across 24 Ω resistor is 12 V. What is the current through the resistor?

  5. Five resistors are connected in the configuration as shown in the figure. Calculate the equivalent resistance between the points a and b.

  6. Explain the determination of unknown resistance using meter bridge.

  7. Let the magnetic moment of a bar magnet be \(\overset { \rightarrow }{ { p }_{ m } } \) whose magnetic length is d = 2l and pole strength is qm. Compute the magnetic moment of the bar magnet when it is cut into two pieces
    (a) along its length
    (b) perpendicular to its length.

  8. A coil of a tangent galvanometer of diametre 0.24 m has 100 turns. If the horizontal
    component of Earth’s magnetic field is 25 × 10-6 T then, calculate the current
    which gives a deflection of 60o.

  9. Deduce the relation for the magnetic induction at a point due to an infinitely long straight conductor carrying current.

  10. Explain the principle and working of a moving coil galvanometer.

  11. A closed coil of 40 turns and of area 200 cm2, is rotated in a magnetic field of flux density 2 Wb m-2. It rotates from a position where its plane makes an angle of 30o with the field to a position perpendicular to the field in a time 0.2 sec. Find the magnitude of the emf induced in the coil due to its rotation.

  12. The current flowing in the first coil changes from 2 A to 10 A in 0.4 sec. Find the mutual inductance between two coils if an emf of 60 mV is induced in the second coil. Also determine the induced emf in the second coil if the current in the first coil is changed from 4 A to 16 A in 0.03 sec. Consider only the magnitude of induced emf.

  13. Define self-inductance of a coil interms of
    (i) magnetic flux and
    (ii) induced emf.

  14. How are the three different emfs generated in a three-phase AC generator? Show the graphical representation of these three emfs.

  15. The relative magnetic permeability of the medium is 2.5 and the relative electrical permittivity of the medium is 2.25. Compute the refractive index of the medium.

  16. What is emission spectra?. Give their types.

  17. Obtain lens maker's formula and mention its significance.

  18. Discuss about simple microscope and obtain the equations for magnification for near point focusing and normal focusing.

  19. Light travelling through transparent oil enters in to glass of refractive index 1.5. If the refractive index of glass with respect to the oil is 1.25, what is the refractive index of the oil?

  20. A monochromatic light is incident on an equilateral prism at an angle 30o and emerges at an angle of 75o. What is the angle of deviation produced by the prism?

  21. Explain why photoelectric effect cannot be explained on the basis of wave nature of light

  22. Describe briefly Davisson Germer experiment which demonstrated the wave nature of electrons.

  23. Explain the J.J. Thomson experiment to determine the specific charge of electron

  24. Explain the idea of carbon dating.

  25. The Bohr atom model is derived with the assumption that the nucleus of the atom is stationary and only electrons revolve around the nucleus. Suppose the nucleus is also in motion, then calculate the energy of this new system.

  26. Explain the construction and working of a full wave rectifier.

  27. State Boolean laws. Elucidate how they are used to simplify Boolean expressions with suitable example.

  28. In a transistor connected in the common base configuration, α = 0.95, IB = mA. Calculate the values of IC and IB

  29. Elaborate on the basic elements of communication system with the necessary block diagram.

  30. What are the possible harmful effects of usage of Nanoparticles? Why?


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