HSC Science (Electronics) 12th Board ExamMaharashtra State Board
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# Question Paper Solutions - Physics 2013 - 2014 HSC Science (Electronics) 12th Board Exam

SubjectPhysics
Year2013 - 2014 (March)

Marks: 70
[12]1 | Attempt any SIX
[2]1.1

Explain the rise of liquid in the capillary on the basis of pressure difference.

Chapter: [6] Surface Tension
Concept: Capillarity and Capillary Action
[2]1.2

Show graphical representation of energy distribution spectrum of perfectly black body.

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Qualitative Ideas of Blackbody Radiation
[2]1.3

The escape velocity of a body from the surface of the earth is 11.2 km/s. If a satellite were to orbit close to the surface, what would be its critical velocity?

Chapter: [2] Gravitation
Concept: Binding Energy and Escape Velocity of a Satellite
[2]1.4

A pipe which is open at both ends is 47 cm long and has an inner diameter 5 cm. If the speed of sound in air is 348 m/s, calculate the fundamental frequency of air column in that pipe.

Chapter: [8] Stationary Waves
Concept: Study of Vibrations of Air Columns
[2]1.5

Show that R.M.S. velocity of gas molecules is directly proportional to square root of its absolute temperature.

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Kinetic Theory of Gases- Assumptions
[2]1.6

For a particle performing uniform circular motion vecv=vecomegaxxvecrobtain an expression for linear acceleration of the particle performing non-uniform circular motion.

Chapter: [1] Circular Motion
Concept: Uniform Circular Motion
[2]1.7

A stone of mass 1 kg is whirled in horizontal circle attached at the end of a 1 m long string. If the string makes an angle of 30º with vertical, calculate the centripetal force acting on the stone.(g=9.8m/s2).

Chapter: [1] Circular Motion
Concept: Centrifugal Forces
[2]1.8

A solid cylinder of uniform density of radius 2 cm has mass of 50 g. If its length is 12 cm, calculate its moment of inertia about an axis passing through its centre and perpendicular to its length.

Chapter: [3] Angular Momentum
Concept: Physical Significance of M.I (Moment of Inertia)
[9]2 | Attempt any THREE:
[3]2.1

Derive an expression for acceleration due to gravity at depth ‘d’ below the earth’s surface.

Chapter: [2] Gravitation
Concept: Acceleration Due to Gravity and Its Variation with Altitude and Depth
[3]2.2

A copper metal cube has each side of length 1 m. The bottom edge of the cube is fixed and tangential force 4.2x108 N is applied to a top surface. Calculate the lateral displacement of the top surface if modulus of rigidity of copper is 14x1010 N/m2.

Chapter: [4] Oscillations
Concept: Periodic and Oscillatory Motions
[3]2.3

State an expression for K. E. (kinetic energy) and P. E. (potential energy) at displacement ‘x’ for a particle performing linear S.H. M. Represent them graphically. Find the displacement at which K. E. is equal to P. E.

Chapter: [4] Oscillations
Concept: K.E.(Kinetic Energy) and P.E.(Potential Energy) in S.H.M.
[3]2.4

The equation of simple harmonic progressive wave is given by y=0.05sinpi[20t-x/6] where all quantities are in S. I. units. Calculate the displacement of a particle at 5 m from origin and at the instant 0.1 second.

Chapter: [7] Wave Motion
Concept: Simple Harmonic Progressive Waves,
[7]3 | Attempt Any One
[7]3.1
[4]3.1.1

State the theorem of parallel axes about moment of inertia.

Chapter: [3] Angular Momentum
Concept: Physical Significance of M.I (Moment of Inertia)

Prove the theorem of parallel axes about moment of inertia

Chapter: [3] Angular Momentum
Concept: Theorems of Perpendicular and Parallel Axes
[3]3.1.2

Calculate the density of paraffin oil, if glass capillary of diameter 0.25 mm dipped in paraffin oil of surface tension 0.0245 N/m rises to a height of 4 cm. (Angle of contact of paraffin with glass = 28° and acceleration due to gravity = 9.8 m/s2.)

Chapter: [6] Surface Tension
Concept: Capillarity and Capillary Action
[7]3.2
[5]3.2.1

A wire of density ‘ρ’ and Young’s modulus ‘Y’ is stretched between two rigid supports separated by a distance ‘L’ under tension ‘T’. Derive an expression for its frequency in fundamental mode. Hence show that n=1/(2L)sqrt((Yl)/(rhoL)) where symbols have their usual meanings

Chapter: [7] Wave Motion
Concept: Reflection of Transverse and Longitudinal Waves
[2]3.2.2

When the length of a simple pendulum is decreased by 20 cm, the period changes by 10%. Find the original length of the pendulum.

Chapter: [4] Oscillations
Concept: Some Systems Executing Simple Harmonic Motion
[7]4 | Select and write the most appropriate answer from the given alternatives for each sub-question
[1]4.1

The bulging of earth at the equator and flattening at the poles is due to _______.

(A) centripetal force

(B) centrifugal force

(C) gravitational force

(D) electrostatic force

Chapter: [1] Circular Motion
Concept: Centrifugal Forces
[1]4.2

Young’s modulus of material of wire is ‘Y’ and strain energy per unit volume is ‘E’, then the strain is

(A) sqrtY/(2E)

(B) sqrt(E/Y)

(C) sqrt((2E)/Y)

(D) sqrt(2EY)

Chapter: [5] Elasticity
Concept: Hooke’s Law
[1]4.3

The wavelength range of thermal radiation is

(A) from 4000 Å to 7000 Å

(B) from 7700 Å to 4 x 106 Å

(C) from 106 Å to 108 Å

(D) from 4 x 10-12 Å to 4 x 108 Å

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Qualitative Ideas of Blackbody Radiation
[1]4.4

A pipe open at both ends resonates to a frequency ‘n1’ and a pipe closed at one end resonates to a frequency ‘n2’. If they are joined to form a pipe closed at one end, then the fundamental frequency will be ______.

(A)  (n_1n_2)/(2n_2+n_1)

(B) (2n_2n_1)/(2n_2+n_1)

(C) (2n_2n_1)/(n_1+n_2)

(D) (n_2+2n_1)/(n_1n_2)

Chapter: [8] Stationary Waves
Concept: Study of Vibrations of Air Columns
[1]4.5

The phase difference between displacement and acceleration of a particle performing S.H.M. is _______.

(A) pi/2rad

(D)(3pi)/2rad

Chapter: [4] Oscillations
Concept: Some Systems Executing Simple Harmonic Motion
[1]4.6

Let n1 and n2 be the two slightly different frequencies of two sound waves. The time interval between waxing and immediate next waning is ______.

(A) 1/(n_1-n_2)

(B) 2/(n_1-n_2)

(C) (n_1-n_2)/2

(D) 1/(2(n_1-n_2))

Chapter: [7] Wave Motion
Concept: Formation of Beats
[1]4.7

A metal ball cools from 64 °C to 50 °C in 10 minutes and to 42 °C in next 10 minutes. The ratio of rates of fall of temperature during the two intervals is _______.

(A) 4/7

(B) 7/4

(C) 2

(D) 2.5

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Temperature and Heat
[12]5 | Attempt any SIX
[2]5.1

Show that the orbital magnetic dipole moment of a revolving electron is (eVr)/2

Chapter: [15] Magnetism
Concept: Magnetic Dipole Moment of a Revolving Electron
[2]5.2

Describe the construction of photoelectric cell.

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Wave Nature of Matter
[2]5.3

For a glass plate as a polariser with refractive index 1.633, calculate the angle of incidence at which light is polarised.

Chapter: [10] Wave Theory of Light
Concept: Polarisation
[2]5.4

The susceptibility of magnesium at 300 K is 2.4 x 10-5. At what temperature will the susceptibility increase to 3.6 x 10-5?

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Temperature and Heat
[2]5.5

Draw a neat labelled diagram for Davisson and Germer experiment, for diffraction of electron wave.

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Davisson-Germer Experiment
[2]5.6

Write the functions of the following in communication systems:

Transmitter

Chapter: [20] Communication Systems
Concept: Basic Terminology Used in Electronic Communication Systems

Write the functions of the following in communication systems:

Chapter: [20] Communication Systems
Concept: Basic Terminology Used in Electronic Communication Systems
[2]5.7

A metal rod 1/sqrtpi m long rotates about one of its ends perpendicular to a plane whose magnetic induction is 4 x 10-3 T. Calculate the number of revolutions made by the rod per second if the e.m.f. induced between the ends of the rod is 16 mV.

Chapter: [16] Electromagnetic Inductions
Concept: Electromagnetic Induction
[2]5.8

Find the wave number of a photon having energy of 2.072 eV

Given : Charge on electron = 1.6 x 10-19 C,

Velocity of light in air = 3 x 108 m/s,

Planck’s constant = 6.63 x 10-34 J-s.

Chapter: [17] Electrons and Photons
Concept: Einstein’s Equation - Particle Nature of Light
[9]6 | Attempt any THREE
[3]6.1

State Ampere’s circuital law.

Chapter: [14] Magnetic Effects of Electric Current
Concept: Ampere’s Circuital Law

Obtain an expression for magnetic induction along the axis of the toroid.

Chapter: [14] Magnetic Effects of Electric Current
Concept: Ampere’s Circuital Law
[3]6.2

Calculate the radius of second Bohr orbit in hydrogen atom from the given data.

Mass of electron = 9.1 x 10-31kg

Charge on the electron = 1.6 x 10-19 C

Planck’s constant = 6.63 x 10-34 J-s.

Permittivity of free space = 8.85 x 10-12 C2/Nm2

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Bohr'S Model for Hydrogen Atom
[3]6.3

Explain the working of P-N junction diode in forward and reverse biased mode.

Chapter: [19] Semiconductors
Concept: Semiconductor Diode
[3]6.4

A network of four capacitors of 6 μF each is connected to a 240 V supply. Determine the charge on each capacitor.

Chapter: [12] Electrostatics
Concept: Condensers in Series and Parallel,
[7]7 | Attempt Any One
[7]7.1
[5]7.1.1

Describe biprism experiment to find the wavelength of monochromatic light. Draw the necessary ray diagram for magnified and diminished images of virtual sources.

Chapter: [11] Interference and Diffraction
Concept: Measurement of Wavelength by Biprism Experiment
[2]7.1.2

If the difference in velocities of light in glass and water is 2.7 x 107 m/s, find the velocity of light in air. (Refractive index of glass = 1.5, Refractive index of water = 1.333)

Chapter: [1] Circular Motion
Concept: Equation for Velocity and Energy at Different Positions of Vertical Circular Motion
[7]7.2
[4]7.2.1

Explain transformer working with construction.

Chapter: [16] Electromagnetic Inductions
Concept: Transformers

State the principle on  which transformer works.

Chapter: [16] Electromagnetic Inductions
Concept: Transformers

Derive an expression for ratio of e.m.f.s and currents in terms of number of turns in primary and secondary coil.

Chapter: [16] Electromagnetic Inductions
Concept: Transformers
[3]7.2.2

Two diametrically opposite points of a metal ring are connected to two terminals of the left gap of meter bridge. The resistance of 11 Ω is connected in right gap. If null point is obtained at a distance of 45 cm from the left end, find the resistance of metal ring.

Chapter: [13] Current Electricity
Concept: Meter Bridge
[7]8 | Select and write the most appropriate answer from the given alternatives for each sub-question
[1]8.1

Intensity of electric field at a point close to and outside a charged conducting cylinder is proportional to ______. (r is the distance of a point from the axis of cylinder)

(A) 1/r

(B) 1/r^2

(C) 1/r^3

(D) r3

Chapter: [12] Electrostatics
Concept: Energy of Charged Condenser
[1]8.2

When a hole is produced in P-type semiconductor, there is _______.

(A) extra electron in valence band.

(B) extra electron in conduction band.

(C) missing electron in valence band.

(D) missing electron in conduction band.

Chapter: [19] Semiconductors
Concept: Electrical Properties - Applications of N-type and P-type Semiconductors
[1]8.3

The outermost layer of the earth’s atmosphere is _______.

(A) stratosphere

(B) mesospher

(C) troposphere

(D) ionosphere

Chapter: [20] Communication Systems
Concept: Propagation of Electromagnetic Waves
[1]8.4

Accuracy of potentiometer can be easily increased by ______

(A) increasing resistance of wire

(B) decreasing resistance of wire

(C) increasing the length of wire

(D) decreasing the length of wire

Chapter: [13] Current Electricity
Concept: Metre Bridge
[1]8.5

When electron in hydrogen atom jumps from second orbit to first orbit, the wavelength of radiation emitted is λ. When electron jumps from third orbit to first orbit, the wavelength of emitted radiation would be _______.

(A)27/32lambda

(B)32/27lambda

(C)2/3lambda

(D)3/2lambda

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Qualitative Ideas of Blackbody Radiation
[1]8.6

An ideal voltmeter has _______.

(A) low resistance

(b) high resistance

(C) infinite resistance

(D) zero resistance

Chapter: [14] Magnetic Effects of Electric Current
Concept: Moving Coil Galvanometer
[1]8.7

The resolving power of telescope of aperture 100 cm for light of wavelength 5.5 x 10-7 m

(A) 0.149 x 10+7

(B) 1.49 x 10+7

(C) 14.9 x 10+7

(D) 149 x 10+7

Chapter: [11] Interference and Diffraction
Concept: Resolving Power of a Microscope and Telescope
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