HSC Science (General) 12th Board ExamMaharashtra State Board
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# Question Paper Solutions - Physics 2014 - 2015 HSC Science (General) 12th Board Exam

Marks: 70
[7]1 | Select and write the most appropriate answer from the given alternatives for each sub-question :
[1]1.1

The period of a conical pendulum in terms of its length (l), semivertical angle (θ) and acceleration due to gravity (g) is:

(a)1/(2pi)sqrt((l costheta)/g)

(b)1/(2pi)sqrt((l sintheta)/g)

(c)4pisqrt((lcostheta)/(4g))

(d)4pisqrt((l tantheta)/g)

Chapter: [4] Oscillations
Concept: Some Systems Executing Simple Harmonic Motion
[1]1.2

The kinetic energy of a rotating body depends upon................

1. distribution of mass only.
2. angular speed only.
3. distribution of mass and angular speed.
4. angular acceleration only.
Chapter: [3] Angular Momentum
Concept: Definition of M.I., K.E. of Rotating Body
[1]1.3

If the metal bob of a simple pendulum is replaced by a wooden bob of the same size, then its time period will.....................

1. increase
2. remain same
3. decrease
4. first increase and then decrease.
Chapter: [4] Oscillations
Concept: Some Systems Executing Simple Harmonic Motion
[1]1.4

The graph between applied force and change in the length of wire within elastic limit is a.......................

1. straight line with positive slope.
2. straight line with negative slope.
3. curve with positive slope.
4. curve with negative slope.
Chapter: [5] Elasticity
Concept: Definition of Stress and Strain
[1]1.5

When longitudinal wave is incident at the boundary of denser medium, then............................

1. compression reflects as a compression.
2. compression reflects as a rarefaction.
3. rarefaction reflects as a compression.
4. longitudinal wave reflects as transverse wave.
Chapter: [7] Wave Motion
Concept: Reflection of Transverse and Longitudinal Waves
[1]1.6

The dimensions of universal gravitational constant are........................

a. [L1M0T0]

b. [L2M1T0]

c. [L-1M1T-2]

d. [L3M-1T-2]

Chapter: [2] Gravitation
Concept: Newton’s Law of Gravitation
[1]1.7

Two copper spheres of radii 6 cm and 12 cm respectively are suspended in an evacuated enclosure. Each of them are at a temperature 15°C above the surroundings. The ratio of their rate of loss of heat is.................

1. 2:1
2. 1:4
3. 1:8
4. 8:1
Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Temperature and Heat
[12]2 | Attempt any Six
[2]2.1

In circular motion, assuming bar v = bar w xx bar r , obtain an expression for the resultant acceleration of a particle in terms of tangential and radial component.

Chapter: [1] Circular Motion
[2]2.2

Explain why an astronaut in an orbiting satellite has a feeling of weightlessness.

Chapter: [2] Gravitation
Concept: Weightlessness
[2]2.3
[1]2.3.1

State the theorem of parallel axes about moment of inertia.

Chapter: [3] Angular Momentum
Concept: Physical Significance of M.I (Moment of Inertia)
[1]2.3.2

State the theorem of perpendicular axes about moment of inertia.

Chapter: [3] Angular Momentum
Concept: Theorems of Perpendicular and Parallel Axes
[2]2.4

State Wein's displacement law

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Wein'S Displacement Law
[1]2.4.1

State Wein's displacement law

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Wein'S Displacement Law
[1]2.4.2

State the First law of thermodynamics.

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Chemical Thermodynamics and Energetic - First Law of Thermodynamics
[2]2.5

A particle in S.H.M. has a period of 2 seconds and amplitude of 10 cm. Calculate the acceleration when it is at 4 cm from its positive extreme position.

Chapter: [4] Oscillations
Concept: Simple Harmonic Motion
[2]2.6

The surface tension of water at 0°C is 75.5 dyne/cm. Calculate surface tension of water at 25°C.

(α for water = 2.7×10-3/°C)

Chapter: [6] Surface Tension
Concept: Surface Tension
[2]2.7

The spin dryer of a washing machine rotating at 15 r.p.s. slows down to 5 r.p.s. after making 50 revolutions. Find its angular acceleration.

Chapter: [1] Circular Motion
Concept: Angular Acceleration
[2]2.8

Calculate the period of revolution of Jupiter around the Sun. The ratio of the radius of Jupiter’s orbit to that of the Earth’s orbit is 5.

(Period of revolution of the Earth is 1 year)

Chapter: [1] Circular Motion
Concept: Vertical Circular Motion Due to Earth’s Gravitation
[9]3 | Attempt any Three
[3]3.1

Derive an expression for excess pressure inside a drop of liquid.

Chapter: [6] Surface Tension
Concept: Surface Tension
[3]3.2

Explain what is Doppler effect in sound

Chapter: [7] Wave Motion
Concept: Beats

Explain what is Doppler effect in sound

Chapter: [10] Wave Theory of Light
Concept: Beats

State any four applications of Doppler effect

Chapter: [7] Wave Motion
Concept: Beats

State any four applications of Doppler effect

Chapter: [10] Wave Theory of Light
Concept: Beats
[3]3.3

Calculate the average molecular kinetic energy :

(a) per kilomole, (b) per kilogram, of oxygen at 27°C.

(R = 8320 J/k mole K, Avogadro's number = 6*03 x 1026 molecules/K mole)

Chapter: [4] Oscillations
Concept: K.E.(Kinetic Energy) and P.E.(Potential Energy) in S.H.M.
[3]3.4

A uniform steel rod of 5 mm2 cross section is heated from 0°C to 25°C. Calculate the force which must be exerted to prevent it from expanding. Also calculate strain.

(α for steel = 12 x 10-6/°C and γ for steel = 20 x 101ON/m2)

Chapter: [5] Elasticity
Concept: Definition of Stress and Strain
[7]4 | Attempt any One
[7]4.1

What are the forced vibrations and resonance?

Chapter: [8] Stationary Waves
Concept: Free and Forced Vibrations

Show that only odd harmonics are present in an air column vibrating in a pipe closed at one end.

Chapter: [8] Stationary Waves
Concept: Free and Forced Vibrations

A stretched wire emits a fundamental note of frequency 256 Hz. Keeping the stretching force constant and reducing the length of wire by 10 cm, the frequency becomes 320 Hz. Calculate the original length of wire.

Chapter: [8] Stationary Waves
Concept: Free and Forced Vibrations
[7]4.2

Obtain an expression for potential energy of a particle performing simple harmonic motion. Hence evaluate the potential energy

1. at mean position and
2. at extreme position.
Chapter: [4] Oscillations
Concept: K.E.(Kinetic Energy) and P.E.(Potential Energy) in S.H.M.
[7]5
[1]5.1

Electric field intensity in free space at a distance ‘r’ outside the charged conducting sphere of radius ‘R’ in terms of surface charge density ‘ a ’ is............................

(a)sigma / in_0[R/r]^2

(b)in_0/sigma[R/r]^2

(c)R/r[sigma/in_0]^2

(d)R/sigma[r/in_0]^2

Chapter: [16] Electromagnetic Inductions
Concept: Electromagnetic Induction
[1]5.2

Instrument which can measure terminal potential difference as well as electro motive force (e.m. f.) is................................

1. Wheatstone’s meter bridge
2. Voltmeter
3. Potentiometer
4. Galvanometer
Chapter: [13] Current Electricity
Concept: Metre Bridge
[1]5.3

If the frequency of incident light falling on a photosensitive material is doubled, then the kinetic energy of the emitted photoelectron will‘be........................................

1. same as its initial value
2. two times its initial value
3. more than two times its initial value
4. less than two times its initial value
Chapter: [4] Oscillations
Concept: K.E.(Kinetic Energy) and P.E.(Potential Energy) in S.H.M.
[1]5.4

Linear momentum of an electron in Bohr orbit of H-atom (principal quantum number n) is proportional to..................................

1. 1/n2
2. 1/n
3. n
4. n2
Chapter: [18] Atoms, Molecules and Nuclei
Concept: Bohr'S Model for Hydrogen Atom
[1]5.5

In a semiconductor, acceptor impurity is.................................

1. antimony
2. indium
3. phosphorous
4. arsenic
Chapter: [19] Semiconductors
Concept: Electrical Properties - Applications of N-type and P-type Semiconductors
[1]5.6

The power radiated by linear antenna of length T is proportional to........................

(λ= wavelength)

1. lambda/ l
2. [lambda/l]^2
3. l/lambda
4. [l/lambda]^2
Chapter: [20] Communication Systems
Concept: Need for Modulation and Demodulation
[1]5.7

The numerical aperture of objective of a microscope is 0.12. The limit of resolution, when light of wavelength 6000A is used to view an object is.......................

1. 0.25 * 10-7m
2. 2.5 * 10-7m
3. 25 * 10-7m
4. 250 * 10-7m

Chapter: [11] Interference and Diffraction
Concept: Resolving Power of a Microscope and Telescope
[12]6 | Attempt any Six
[2]6.1

What is a Polaroid?

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

State two uses of Polaroid.

Chapter: [10] Wave Theory of Light
Concept: Polarisation
[2]6.2

Draw a neat and labelled diagram of suspended coil type moving coil galvanometer.

Chapter: [14] Magnetic Effects of Electric Current
Concept: Moving Coil Galvanometer
[2]6.3

Define Magnetization

Chapter: [15] Magnetism
Concept: Magnetisation and Magnetic Intensity

Define Magnetic intensity.

Chapter: [15] Magnetism
Concept: Magnetisation and Magnetic Intensity
[2]6.4

Draw a block diagram of generalized communication system.

Chapter: [20] Communication Systems
Concept: Elements of a Communication System
[2]6.5

A solenoid 3.142m long and 5.0 cm in diameter has two layers of windings of 500 turns each and carries a current of 5A. Calculate the magnetic induction at its centre along the axis.

Chapter: [16] Electromagnetic Inductions
Concept: Inductance and Capacitance
[2]6.6

A circular coil of 300 turns and average area 5 * 10-3m2 carries a current of 15A. Calculate the magnitude of magnetic moment associated with the coil.

Chapter: [15] Magnetism
Concept: Magnetic Dipole Moment of a Revolving Electron
[2]6.7

The magnetic flux through a loop varies according to the relation Φ = 8t2 + 6t + C, where ‘C’ is constant, 'Φ' is in milliweber and 't' is in second. What is the magnitude of induced e.m.f. in the loop at t = 2 seconds.

Chapter: [16] Electromagnetic Inductions
Concept: Electromagnetic Induction
[2]6.8

An electron is orbiting in 5th Bohr orbit. Calculate ionisation energy for this atom, if the ground state energy is -13.6 eV.

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Bohr'S Model for Hydrogen Atom
[9]7 | Attempt any Three
[3]7.1

Obtain an expression for the radius of Bohr orbit for H-atom.

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Bohr'S Model for Hydrogen Atom
[3]7.2

What are α and β parameters for a transistor? Obtain a relation between them.

Chapter: [19] Semiconductors
Concept: Transistor and Characteristics of a Transistor
[3]7.3

Two metal spheres having charge densities 5μC/m2 and -2μC/m2 with radii 2mm and  1mm respectively are kept in a hypothetical closed surface. Calculate total normal electric induction over the closed surface.

Chapter: [16] Electromagnetic Inductions
Concept: Inductance and Capacitance
[3]7.4

The threshold wavelength of silver is 3800Å. Calculate the maximum kinetic energy in eV of photoelectrons emitted, when ultraviolet light of wavelength 2600Å falls on it.

(Planck’s constant, h =6.63 x 1O-34J.s.,

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

Chapter: [17] Electrons and Photons
Concept: Einstein’s Equation - Particle Nature of Light
[7]8 | Attempt any One
[7]8.1

Obtain an expression for e.m.f. induced in a coil rotating with uniform angular velocity in a uniform magnetic field. Show graphically the variation of e.m.f. with time (t).

Resistance of a potentiometer wire is 0.1Ω/cm. A cell of e.m.f 1.5V is balanced at 300 cm on this potentiometer wire. Calculate the current and balancing length for another cell of e.m.f. 1.4V on the same potentiometer wire.

Chapter: [16] Electromagnetic Inductions
Concept: Coil Rotating in Uniform Magnetic Induction
[7]8.2

Describe biprism experiment to calculate the wavelength of a monochormatic light. Draw the necessary ray diagram.

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

If the critical angle of a medium is sin-1(3/5), find the polarising angle.

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