Physics | RJ Board | Grade 12 | 2015
Q. Define common emitter output characteristic for a transistor. Draw a circuit diagram for studying the characteristics of n-p-n transistor in common emitter configuration.
Among emitter, base and collector regions of a transistor which one is:
(a) largest in size and (b) most heavily doped?
View Solution
Q. Draw propagation diagram of a linearly polarised electromagnetic wave and write any two properties of electromagnetic waves.
The amplitude of the magnetic field associated with an electromagnetic wave in vacuum is B0=50×108 tesla. Write the value of amplitude of the electric field in V/m associated with the wave.
View Solution
Q. A ray of light is incident at the Brewster's angle on the surface of a transparent medium. Deduce Brewster's law by using Snell's law.
View Solution
Q. Write the relation between object distance (u), image distance (v) and focal length (f) for a concave mirror.
View Solution
Q. Write the statement of Gauss's law.
View Solution
Q. On the basis of Bohr's postulates derive an expression for orbital velocity of an electron in nth stationary orbit of hydrogen atom.
The ground state energy of hydrogen atom is (X) eV. What will be the kinetic energy of the electron in this state?
View Solution
Q. Define half-life of a radioactive substance and write the relation of half-life with the following:
(a) Radioactive decay constant (disintegration constant)
(b) Mean life of a radioactive substance.
View Solution
Q. Match the following:
 Column I Column II (a) Resonant frequency (i) VIcosϕ (b) Quality factor (ii) 12LI2 (c) Average power (iii) 1√LC (d) Impedance (iv) √R2+(XL−XC)2 (e) Magnetic potential energy (v) −E(dIdt) (f) Coefficient of self-induction (vi) w0LR

1. aiii, bv, ci, div, evi, fii
2. aii, biv, cv, diii, evi, fi
3. aii, biii, ci, div, ev, fvi
4. none of these
View Solution
Q. Write the relation in radius R and mass number A of a nucleus.
View Solution
Q. Define angle of inclination (magnetic declination).
In the magnetic meridian of a certain place, the horizontal component of earth's magnetic field is 0.25 gauss and the dip angle is 60o. At this place find the value of earth's magnetic field.
View Solution
Q. A message signal of peak voltage 20V is used to modulate a carrier wave of peak voltage 30V. Determine the modulation index.
View Solution
Q.

(i) Define rectification.
(ii) Draw a circuit diagram of a full-wave rectifier.
(iii) Semi-conductor related to given energy band diagram is:
n-type semi-conductor, p-type semi-conductor or intrinsic semi-conductor.

View Solution
Q. (a) Write the name of the lens used to correct nearsightedness (myopia)
(b) What will be the radius of curvature of a concave mirror of focal length 10cm?
View Solution
Q. Define the following:
(a) Total internal reflection
(b) Diffraction of light
(c) Refraction of light
View Solution
Q. How the effective power radiated by an antenna will be changed if the wavelength of radiation is decreased?
View Solution
Q. Calculate the potential at a point due to a charge of 3×109C located 9×102m away from it.
View Solution
Q. Define mass defect of a nucleus. Binding energy of 8O16 is 127.5MeV. Write the value of its 'binding energy per nucleon'. Write the value of 1eV energy in joule.
View Solution
Q. In the figure, resistivities of two conductors of same material are ρ1Ωm and ρ2Ωm respectively. Write the value of ratio of ρ1 and ρ2

View Solution
Q. Select one donor impurity among the following:
Boron(B), Aluminium (Al), and Arsenic (As).
View Solution
Q. Write de Broglie hypothesis. Obtain the formula for de Broglie wavelength of an electron which is accelerated from rest through a potential V volt.
View Solution
Q. (a) Derive a relation for electric field due to an electric dipole at a point on the equatorial plane of the electric dipole. Draw necessary diagram.
(b) An electric dipole of charge ±1 μC exists inside a spherical Gaussian surface of radius 1cm. Write the value of outgoing flux from the Gaussian surface.
(c) Potential on the surface of a charged spherical shell of radius 10cm is 10V. Write the value of potential at 5cm from its centre.
View Solution
Q. Write the name of electromagnetic wave produced by vacuum tube magnetron.
View Solution
Q. Explain briefly the following terms used in communication system:
(a) modulation; and (b) transducer.
View Solution
Q. Write average value of current over a complete cycle of alternating current.
View Solution
Q. Write the statement of Lenz's law of electromagnetic induction.
A 2m horizontal long straight conducting wire extending from east to west direction is falling with a speed of 5m/s perpendicular to the horizontal component of the earth's magnetic field 0.3×104 tesla. Calculate the value of instantaneous emf induced across the ends of wire.
View Solution
Q. (a) NAND gates are also called universal gate. Why?
(b) Draw a logic symbol of OR gate.
(c) Write the value of output y in the given circuit:
(d) Write the name of the diode used in voltage regulation.

View Solution