HSC Science (Electronics) 12th Board ExamMaharashtra State Board
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Question Paper Solutions - Physics 2016 - 2017 HSC Science (Electronics) 12th Board Exam


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

If the angular speed of the earth is 7.26 x 10–5 rad/s and radius of the earth is 6,400 km,
calculate the change in weight of 1 kg of mass taken from equator to pole.

Chapter: [1] Circular Motion
Concept: Angular Velocity
[2]1.ii

A small body of mass 0.3 kg oscillates in vertical plane with the help of a string 0.5 m long with a constant speed of 2 m/s. It makes an angle of 60° with the vertical. Calculate tension in the string (g = 9.8 m/s2).

Chapter: [5] Elasticity
Concept: Definition of Stress and Strain
[2]1.iii

Two soap bubbles have radii in the ratio 4:3. What is the ratio of work done to blow these bubbles?

Chapter: [6] Surface Tension
Concept: Capillarity and Capillary Action
[2]1.iv

At what temperature will average kinetic energy of gas be exactly half of its value at N.T.P.?

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Kinetic Theory of Gases- Assumptions
[2]1.v

Define surface tension and surface energy.

Chapter: [6] Surface Tension
Concept: Surface Tension
[2]1.vi

Prove that `g_h=g(1-"2h"/R)` where gh is the acceleration due to gravity at altitude h and h << R (R is the radius of the earth).

Chapter: [2] Gravitation
Concept: Acceleration Due to Gravity and Its Variation with Altitude and Depth
[2]1.vii

Explain the physical significance of radius of gyration

Chapter: [3] Angular Momentum
Concept: Physical Significance of M.I (Moment of Inertia)
[2]1.viii

Draw a diagram showing all components of forces acting on a vehicle moving on a curved banked road. 

Chapter: [1] Circular Motion
Concept: Banking of Roads

Write the necessary equation for maximum safety, speed and state the significance of each term involved in it.

Chapter: [1] Circular Motion
Concept: Banking of Roads
[9]2 | Attempt any THREE:
[3]2.i

Prove Kirchhoff’s law of radiation theoretically.

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Qualitative Ideas of Blackbody Radiation
[3]2.ii

Within the elastic limit, find the work done by a stretching force on a wire.

Chapter: [5] Elasticity
Concept: Elastic Energy
[3]2.iii

A set of 12 tuning forks is arranged in order of increasing frequencies. Each fork produces
‘Y’ beats per second with the previous one. The last is an octave of the first. The fifth fork
has a frequency of 90 Hz. Find ‘Y’ and frequency of the first and the last tuning forks.

Chapter: [7] Wave Motion
Concept: Formation of Beats
[3]2.iv

A uniform solid sphere has radius 0.2 m and density 8 x 103 kg/m3. Find the moment of
inertia about the tangent to its surface. (π = 3.142)

Chapter: [3] Angular Momentum
Concept: Physical Significance of M.I (Moment of Inertia)
[7]3 | Attempt any one of the following
[7]3.i

Define linear simple harmonic motion.

Chapter: [4] Oscillations
Concept: Simple Harmonic Motion

Assuming the expression for displacement of a particle starting from extreme position, explain graphically the variation of velocity and acceleration w.r.t. time.

Chapter: [4] Oscillations
Concept: Simple Harmonic Motion

A clock regulated by seconds pendulum, keeps correct time. During summer, length of pendulum increases to 1.005 m. How much will the clock gain or loose in one day?

(g = 9.8 m/s2 and π = 3.142)

Chapter: [4] Oscillations
Concept: Some Systems Executing Simple Harmonic Motion
[7]3.ii

Discuss different modes of vibrations in an air column of a pipe open at both the ends.

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

State the cause of end correction.

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

Find the end correction for the pipe open at both the ends in fundamental mode.

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

What should be tension applied to a wire of length 1 m and mass 10 gram, if it has to vibrate with fundamental frequency of 50 Hz?

Chapter: [8] Stationary Waves
Concept: Forced Oscillations and Resonance
[7]4 | Select and write the most appropriate answer from the given alternatives for each sub-question:
[1]4.i

A body of mass ‘m’ performs uniform circular motion along a circular path of radius ‘r’ with velocity ‘v’. If its angular momentum is L, then the centripetal force acting on it is

(A) `(mL^2)/r^3`

(B) `L^2/(mr)`

(c) `L^2/(mr^2)`

(D) `L^2/(mr^3)`

Chapter: [1] Circular Motion
Concept: Centrifugal Forces
[1]4.ii

If the Earth completely loses its gravity, then for any body _______.

(A) both mass and weight become zero.
(B) neither mass nor weight become zero.
(C) weight becomes zero but not the mass.
(D) mass becomes zero but not the weight.

Chapter: [2] Gravitation
Concept: Weightlessness
[1]4.iii

If a rigid body of radius ‘R’ starts from rest and rolls down an inclined plane of inclination
‘θ’ then linear acceleration of body rolling down the plane is _______.

(A)`(gsintheta)/(1+K/R)`

(B) `gsintheta(1+K/R)`

(C) `(gsintheta)/(1+K^2/R^2)`

(D) `gsintheta(1+K^2/R^2)`

Chapter: [3] Angular Momentum
Concept: Rolling Motion
[1]4.iv

1000 tiny mercury droplets coalesce to form a bigger drop. In this process, temperature of the drop _______ .

(A) increases

(B) may increase or decrease

(C) decreases

(D) does not change

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Temperature and Heat
[1]4.v

Doppler effect is not applicable when _______.
(A) source and observer are at rest.
(B) there is a relative motion between source and observer.
(C) both are moving in opposite directions.
(D) both are moving in same direction with different velocities

Chapter: [7] Wave Motion
Concept: Beats

Doppler effect is not applicable when _______.
(A) source and observer are at rest.
(B) there is a relative motion between source and observer.
(C) both are moving in opposite directions.
(D) both are moving in same direction with different velocities

Chapter: [10] Wave Theory of Light
Concept: Beats
[1]4.vi

If the total kinetic energy per unit volume of gas enclosed in a container is E, the pressure exerted by the gas is

(A) E

(B) 3/2 E

(C) `sqrt3E`

(D) 2/3E

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Kinetic Theory of Gases- Assumptions
[1]4.vii

Two wires of the same material have radii rA and rB respectively. The radius of wire A is twice the radius of wire B. If they are stretched by same load then stress on wire B is 

(A) equal to that of A

(B) half that of A.

(C) two times that of A.

(D) four times that of A.

Chapter: [5] Elasticity
Concept: Eneral Explanation of Elastic Property
[12]5 | Attempt any SIX:
[2]5.i

Thorium 90Th232 is disintegrated into lead 82Pb200. Find the number of α and β particles emitted in disintegration.

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Alpha-particle Scattering and Rutherford’S Nuclear Model of Atom
[2]5.ii

If the work function of a metal is 3 eV, calculate the threshold wavelength of that metal.
(Velocity of light = 3 x 108 m/s, Planck’s constant = 6.63 x 10–34 J.s.; 1 eV = 1.6 x 10–19 J)

Chapter: [11] Interference and Diffraction
Concept: Measurement of Wavelength by Biprism Experiment
[2]5.iii

Three capacitors of capacities 8 μF, 8 μF and 4 μF are connected in a series and potential difference of 120 volt is maintained across the combination. Calculate the charge  on capacitor of capacity 4 μF.

 

Chapter: [16] Electromagnetic Inductions
Concept: Reactance and Impedance
[2]5.iv

If the total energy of radiation of frequency 1014 Hz is 6.63 J, calculate the number of  photons in the radiation. (Planck’s constant = 6.63 x 10–34 J.s.)

Chapter: [17] Electrons and Photons
Concept: Photoelectric Effect - Hertz’S Observations
[2]5.v

Distinguish between diamagnetic and paramagnetic substances

Chapter: [15] Magnetism
Concept: Magnetic Properties of Materials
[2]5.vi

Draw a neat, labeled diagram showing different layers of the Earth’s atmosphere.

Chapter: [20] Communication Systems
Concept: Production and Detection of an Amplitude Modulated Wave
[2]5.vii

Explain the construction of plane wavefront using Huygens’ principle.

Chapter: [10] Wave Theory of Light
Concept: Huygens Principle
[2]5.viii

Obtain an expression for electric field intensity at a point outside uniformly charged thin plane sheet.

Chapter: [12] Electrostatics
Concept: Effect of Dielectric on Capacity
[9]6 | Attempt any THREE:
[3]6.i

Write the functions of three segments of a transistor.

Chapter: [19] Semiconductors
Concept: Junction Transistor - Transistor as an Amplifier (Ce-configuration)

Draw a circuit diagram for studying the input and output characteristics of a n-p-n transistor in common emitter configuration. Using the circuit, explain how input, output characteristics are obtained

Chapter: [19] Semiconductors
Concept: Junction Transistor - Transistor as an Amplifier (Ce-configuration)
[3]6.ii

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.iii

When a resistance of 12 ohm is connected across a cell, its terminal potential difference is balanced by 120 cm length of potentiometer wire. When the resistance of 18 ohm is connected across the same cell, the balancing length is 150 cm. Find the balancing length when the cell is in open circuit. Also calculate the internal resistance of the cell.

Chapter: [13] Current Electricity
Concept: Metre Bridge
[3]6.iv

Find the ratio of longest wavelength in Paschen series to shortest wavelength in Balmer series.

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Wavelength of an Electron
[7]7 | Attempt any one of the following
[7]7.i

State the principle on  which transformer works.

Chapter: [16] Electromagnetic Inductions
Concept: Transformers

Explain transformer working with construction.

Chapter: [16] Electromagnetic Inductions
Concept: Transformers

Derive an expression for e.m.f. and current in terms of turns ratio

Chapter: [16] Electromagnetic Inductions
Concept: Transformers

Find the magnetization of a bar magnet of length 10 cm and cross-sectional area 4 cm2, if the magnetic moment is 2 Am2.

Chapter: [15] Magnetism
Concept: Magnetisation and Magnetic Intensity
[7]7.ii

Derive an expression for path difference in Young’s double slit experiment and obtain the conditions for constructive and destructive interference at a point on the screen.

Chapter: [11] Interference and Diffraction
Concept: Interference of Light Waves and Young’S Experiment

The refractive indices of glass and water w.r.t. air are 3/2 and 4/3 respectively. Determine the refractive index of glass w.r.t. water.

Chapter: [10] Wave Theory of Light
Concept: Polarisation
[7]8 | Select and write the most appropriate answer from the given alternatives for each sub-question:
[1]8.i

The logic gate which produces LOW output when one of the input is HIGH and produces
HIGH output only when all of its inputs are LOW is called _______.

(A) AND gate

(B) OR gate

(C) NOR gate

(D) NAND gate

Chapter: [19] Semiconductors
Concept: Digital Electronics and Logic Gates
[1]8.ii

For efficient radiation and reception of signal with wavelength λ, the transmitting antennas would have length comparable to ______.

(A)`lambda` of frequency used

(B)`lambda/2` of frequency used

(C )`lambda/3` of frequency used

(D)`lambda/4` of frequency used

Chapter: [20] Communication Systems
Concept: Elements of a Communication System
[1]8.iii

Which one of the following particles cannot be accelerated by a cyclotron?

(A) Electrons

(B) Protons

(C) Deuterons

(D) α- particles

Chapter: [14] Magnetic Effects of Electric Current
Concept: Motion in Combined Electric and Magnetic Fields - Cyclotron
[1]8.iv

In series LCR circuit at resonance, phase difference between current and e.m.f. of source is ______.

(A) `pi` rad

(B) `pi/2` rad

(C) `pi/4` rad

(D) zero rad

Chapter: [16] Electromagnetic Inductions
Concept: Resonant Circuit
[1]8.v

When unknown resistance is determined by meter bridge, the error due to contact resistance
is minimized ______.

(A) by connecting both the resistances only in one gap.
(B) by interchanging the positions of known and unknown resistance.
(C) by using uniform wire.
(D) by obtaining the null point near the ends of the wire.

Chapter: [13] Current Electricity
Concept: Meter Bridge
[1]8.vi

The ratio of kinetic energy of an electron in Bohr’s orbit to its total energy in the same orbit  is

(A) – 1

(B) 2

(C) 1/2

(D) – 0.5

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Bohr'S Model for Hydrogen Atom
[1]8.vii

Using monochromatic light of wavelength λ in Young’s double slit experiment, the eleventh dark fringe is obtained on the screen for a phase difference of ______.

(A) `11/2 pi` rad

(B) `21/2 pi` rad

(C) `13 pi` rad

(D) `21 pi` rad

Chapter: [11] Interference and Diffraction
Concept: Interference of Light Waves and Young’S Experiment
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