12th physics question paper 2015 – bihar board

Section – I (Objective Type)
  1. The electric dipole moment of an electric dipole made up of two opposite charges having magnitude + 3.2 x 10-19+C and -3.2 x 10-19C separated by a distance 2.4 x 10-10m is
(a) 7.68 x 10-27 C-m (b) 7.68 x 10-29 C-m
(c) 7.86 x 10-29 C-m (d) 7.86 x 10-27 C-m
  1. 64 Identical drops each of capacity 5µF combine to form a big drop. What is the capacity of big drip?
(a) 164µF (b) 20µF
(c) 4 µF (d) 25 µF
  1. Kilowatt-hour (kWh) is the unit of
(a) energy (b) power
(c) torque (d) force
12th physics question paper 2015 – bihar board

  1. The algebraic sum of all currents meeting at any point in an electrical circuit is
(a) Infinite (b) Positive
(c) Zero (d) Negative
  1. Dimension of permeability is
(a) MLT-2I-2 (b) MLT2I-2
(c) MLT-2I 2 (d) MLT-2I
  1. Impedance of L-R circuit
(a) (b)
(c) (d)
  1. The direction of propagation of electromagnetic wave is
(a) Parallel to (b) Parallel to
(c) Parallel to (d) Parallel to
  1. When a ray of light enters a glass slab, its wavelength
(a) Increases (b) Decreases
(c) Remains unchanged (d) Data are not complete
  1. The value of amplifier modulation index is
(a) always 0 (b) between 1 and ∞
(c) between 0 and 1 (d) always ∞
  1. Boolean expression of NOR gate is
(a) A + B = Y (b)
(c) A . B = Y (d)
  1. The intensity of electricity filed at any point on the surface of a charged conductor is
(a) zero (b) perpendicular to the surface
(c) tangential to the surface (d) at 450 to the surface
  1. Permittivity of free space is
(a) 9 x 109 mF-1 (b) 1.6 x 1019 C
(c) 8.85 x 10-12 Fm-1 (d) 8.85 x 10-9 Fm-1
  1. Power of electric circuit is
(a) V . R (b) V2 . R
(c) (d) V2 . R . I
  1. Electron volt (eV) is the measure of
(a) charge (b) potential difference
(c) current (d) energy
  1. Lens law is associated with
(a) charge
(b) mass
(c) energy
(d) principle of conservation of momentum
  1. The final image in astronomical telescope is
(a) real and erect (b) real and inverted
(c) virtual and inverted (d) virtual and erect
  1. When two converging lenses of same focal length are placed in contact, then the focal length of the combination is
(a) (b) 2
(c) (d) 3
  1. The transverse nature of light wave supports
(a) interference (b) reflection
(c) polarisation (d) dispersion
  1. The colour of a thin film is due to
(a) scattering (b) interference
(c) dispersion (d) diffraction
  1. If ɸ is the phase difference between ac current and e.m.f., then the value of power factor is
(a) tan ɸ (b) cos2 ɸ
(c) sin ɸ (d) cos ɸ
  1. Unit of self-induction is
(a) Weber (b) Ohm
(c) Henry (d) Gauss
  1. The working of dynamo is based on the principle of
(a) hearing effect of current (b) electromagnetic induction
(c) magnetic induction (d) electric induction
  1. The equation of an ac is represented by I = 0.6sin 100 . The frequency of ac is
(a) 50 (b) 50
(c) 100 (d) 100
  1. Nickel is
(a) diamagnetic (b) paramagnetic
(c) ferromagnetic (d) none of these
  1. Brewster’s law is
(a) (b)
(c) (d)
  1. With the increase of temperature, the resistance of a semiconductor
(a) increases
(b) decreases
(c) sometimes increases and sometimes decreases
(d) remains unchanged
  1. The ratio of peak value and r.m.s. value of ac is
(a) 2 (b)
(c) (d)
  1. Which frequency range is used for TV transmission?
(a) 30-300 Hz (b) 30-300 KHz
(c) 30-300 MHz (d) 30-300 GHz

Section – II (Non- Objective Type)
  1. Define electric dipole moment and write its SI units.
  2. Write two main features of Laser rays.
  3. What is the function of second plate in a parallel plate capacitor?
  4. The charge on a metallic sphere of radius 9cm is 4x10-6 C. Calculate the potential energy of charge on the conductor.
  5. When two resistors are connected in series and parallel, then their equivalent resistances are 16Ω and 3 Ω respectively. Find out the resistance of each resistor.
  6. Name the energy losses in a transformer.
  7. The equation of an ac is I=20sin 200 . Find out the frequency, peak value and r.m.s. value of the current.
  8. Tow thin lenses of powers 5D and 2D are placed coaxially at a distance 20cm apart. Find the focal length and power of the combination of lenses.
  9. Distinguish between n-type and p-type semiconductors.
  10. Define modulation. Write its types.
Long Answer Type Questions
  1. Define electric intensity. Derive an expression for electric intensity at a point suited pm the axis of electric dipole.
Define electric flux. State and prove Gauss theorem.
  1. Establish the formula
Write Huygens principles of light wave. Prove the laws of reflection or refraction of light on the basis of Huygens principles of light wave.
  1. Explain Biot-Savart law. With its help derive an expression for the magnetic field at any point on the axis of a current carrying circular loop.
Define Kirchhoff’s laws of electric circuit. Derive an expression for a balanced. Wheat stone’s bridge using Kirchhoff’s law.
  1. Give postulates of Bohr’s theory. Explain hydrogen spectrum on the basis of Bohr’s theory.
Write down Einstein’s photoelectric equation and explain the photoelectric effect on its basis.


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