HSC Science (Electronics) 12th Board ExamMaharashtra State Board
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Question Paper Solutions - Physics 2015 - 2016 HSC Science (Electronics) 12th Board Exam

notes


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

In U. C. M (Uniform Circular Motion), prove the relation `vec v = vec w xx vec r`, where symbols have their usual meanings.

 
 
Chapter: [1] Circular Motion
Concept: Uniform Circular Motion
[2]1.2

Derive an expression for critical velocity of a satellite revolving around the earth in a circular orbit.

Chapter: [2] Gravitation
Concept: Acceleration Due to Gravity and Its Variation with Altitude and Depth
[2]1.3

Obtain an expression for total kinetic energy of a rolling body in the form

`1/2 (MV^2)[1+K^2/R^2]`

 
Chapter: [3] Angular Momentum
Concept: Definition of M.I., K.E. of Rotating Body
[2]1.4

Define emissive power and coefficient of emmision of a body.

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Temperature and Heat
[2]1.5

A coin kept at a distance of 5cm from the centre of a turntable of radius 1.5m just begins to slip when the turntable rotates at a speed of 90 r.p.m. Calculate the coefficient of static friction between the coin and the turntable.

[g = 9.8 m/s2]

Chapter: [1] Circular Motion
Concept: Centrifugal Forces
[2]1.6

The fundamental frequency of an air column in a pipe closed at one end is in unison with the third overtone of an open pipe. Calculate the ratio of lengths of their air columns

Chapter: [8] Stationary Waves
Concept: Study of Vibrations of Air Columns
[2]1.7

A particle performing linear S.H.M. has a period of 6.28 seconds and a pathlength of 20 cm. What is the velocity when its displacement is 6 cm from mean position?

Chapter: [4] Oscillations
Concept: Differential Equation of Linear S.H.M.
[2]1.8

The energy of the free surface of a liquid drop is 5π times the surface tension of the liquid. Find the diameter of the drop in C.G.S. system.

Chapter: [6] Surface Tension
Concept: Surface Tension
[7]2 | Select and write the most appropriate answer from the given alternatives for each sub-question :
[1]2.1

A particle rotates in U.C.M. with tangential velocity V along a horizontal circle of diameter ‘D' . Total angular displacement of the particle in time 't' is..........

(a) vt

(b) (v/D)-t

(c) vt/2D

(d) 2vt/D



 

Chapter: [1] Circular Motion
Concept: Uniform Circular Motion
[1]2.2

Two springs of force constants K1 and K2 (K1> K2) are stretched by same force. If W1 and W2 be the work done stretching the springs then......

(a) W1=W2

(b) W1<W2

(c) W1>W2

(d) W1=W2=0

Chapter: [5] Elasticity
Concept: Elastic Energy
[1]2.3

A and B are two steel wires and the radius of A is twice that of B. If they are stretched by the same load, then the stress on B is .....

(a) four times that of A.

(b) two times that of A.

(c) three times that of A.

(d) same as that of A.

Chapter: [5] Elasticity
Concept: Behaviour of Metal Wire Under Increasing Load
[1]2.4

If sound waves are reflected from surface of denser medium, there is phase change of.......

(a) 0 rad                                    

(b) π/4  rad

(c) π/2 rad    

(d) π rad

Chapter: [8] Stationary Waves
Concept: Forced Oscillations and Resonance
[1]2.5

A sonometer wire vibrates with frequency n1 in air under suitable load of specific gravity of . When the load is immersed in water, the frequency of vibration of wire n2 will be .........

(a)  `n_1sqrt((sigma+1)/sigma)`

(b) `n_1sqrt((sigma-1)/sigma)`

(c) `n_1sqrt(sigma/(sigma+1))`

(d) `n_1sqrt(sigma/(sigma-1))`

 

Chapter: [2] Gravitation
Concept: Acceleration Due to Gravity and Its Variation with Altitude and Depth
[1]2.6

For polyatomic molecules having 'f' vibrational modes, the ratio of two specific heats,Cp/Cv  is..........

(a) `(1+f)/(2+f)`

(b) `(2+f)/(3+f)`

(c) `(4+f)/(3+f)`

(d) `(5+f)/(4+f)`

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Law of Equipartition of Energy
[1]2.7

A body of moment of inertia 5 kgm2 rotating with an angular velocity 6 rad/s has the same kinetic energy as a mass of 20 kg moving with a velocity of ......

(a) 5 m/s

(b) 4 m/s

(c) 3 m/s

(d) 2 m/s

Chapter: [3] Angular Momentum
Concept: Physical Significance of M.I (Moment of Inertia)
[7]3 | Attempt any one of following :
[7]3.1

Define linear S.H.M.

Chapter: [4] Oscillations
Concept: Differential Equation of Linear S.H.M.

Show that S.H.M. is a projection of  U.C.M. on any diameter

Chapter: [4] Oscillations
Concept: Projection of U.C.M.(Uniform Circular Motion) on Any Diameter

A metal sphere cools at the rate of 4°C / min. when its temperature is 50°C. Find its rate of cooling at 45°C if the temperature of surroundings is 25°C.

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Temperature and Heat
[7]3.2

Explain analytically how the stationary waves are formed

Chapter: [8] Stationary Waves
Concept: Formation of Stationary Waves on String

Hence show that the distance between node and adjacent antinode is λ/4

Chapter: [8] Stationary Waves
Concept: Formation of Stationary Waves on String

A set of 48 tuning forks is arranged in a series of descending frequencies such that each fork gives 4 beats per second with preceding one. The frequency of first fork is 1.5 times the frequency of the last fork, find the frequency of the first and 42nd tuning fork

Chapter: [7] Wave Motion
Concept: Formation of Beats
[9]4 | Attempt any THREE
[3]4.1

What is the decrease in weight of a body of mass 600kg when it is taken in a mine of depth 5000m?

[ Radius of earth = 6400km, g = 9.8 m/s2 ]

Chapter: [2] Gravitation
Concept: Acceleration Due to Gravity and Its Variation with Altitude and Depth
[3]4.2
[1]4.2.1

State the theorem of parallel axes about moment of inertia.

Chapter: [3] Angular Momentum
Concept: Physical Significance of M.I (Moment of Inertia)
[2]4.2.2

Prove the theorem of parallel axes about moment of inertia

Chapter: [3] Angular Momentum
Concept: Theorems of Perpendicular and Parallel Axes
[3]4.3

Derive Laplace’s law for spherical membrane of bubble due to surface tension.

Chapter: [6] Surface Tension
Concept: Surface Tension
[3]4.4

A steel wire having cross sectional area 1.5 mm2 when stretched by a load produces a lateral strain 1.5 x 10-5. Calculate the mass attached to the wire.

(Ysteel = 2 x 1011 N/m2, Poisson’s ratio σ = 0.291,g = 9.8 m/s2)

Chapter: [5] Elasticity
Concept: Definition of Stress and Strain
[12]5 | Attempt any SIX
[2]5.1

What is 'diffraction of light'

Chapter: [11] Interference and Diffraction
Concept: Fraunhofer Diffraction Due to a Single Slit

Explain two types of diffraction of light.

Chapter: [11] Interference and Diffraction
Concept: Fraunhofer Diffraction Due to a Single Slit
[2]5.2

Draw a neat labelled diagram for the construction of 'cyclotron'

Chapter: [14] Magnetic Effects of Electric Current
Concept: Motion in Combined Electric and Magnetic Fields - Cyclotron
[2]5.3

Distinguish between ‘paramagnetic’ and ‘ferromagnetic’ substances.

Chapter: [15] Magnetism
Concept: Magnetic Properties of Materials
[2]5.4

Write a short note on surface wave propagation of electromagnetic waves.

Chapter: [20] Communication Systems
Concept: Propagation of Electromagnetic Waves
[2]5.5

The combined resistance of a galvanometer of resistance 500Ω and its shunt is 21Ω. Calculate the value of shunt.

Chapter: [14] Magnetic Effects of Electric Current
Concept: Moving Coil Galvanometer
[2]5.6

The susceptibility of magnesium at 200 K is 1.8 x 10-5. At what temperature will the susceptibility decrease by 6 x 10-6?

Chapter: [15] Magnetism
Concept: Magnetic Properties of Materials
[2]5.7

The co-efficient of mutual induction between primary and secondary coil is 2H. Calculate induced e.m.f. if current of 4A is cut off in 2.5 x 10-4 seconds

Chapter: [16] Electromagnetic Inductions
Concept: Inductance - Mutual Inductance
[2]5.8

The decay constant of radioactive substance is 4.33 x 10-4 per year. Calculate its half life period.

 

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Radioactivity - Law of Radioactive Decay
[7]6 | Select and write the most appropriate answer from the given alternatives for each sub-question :
[7]6.1

If the polarising angle for a given medium is 60°, then the refractive index of the medium is.................

(a) `1/sqrt3`

(b) `sqrt(3/2)`

(c) 1

(d) `sqrt3`

Chapter: [10] Wave Theory of Light
Concept: Polarisation
[1]6.2

The resolving power of a telescope depends upon the...............

(a) length of the telescope

(b) focal length of an objective

(c) diameter of an objective

(d) focal length of an eyepiece

Chapter: [11] Interference and Diffraction
Concept: Resolving Power of a Microscope and Telescope
[1]6.3

Electric intensity due to a charged sphere at a point outside the sphere decreases with...................

(a)increase in charge on sphere.

(b)increase in dielectric constant.

(c)decrease in the distance from the centre of sphere.

(d)decrease in square of distance from the centre of sphere

Chapter: [12] Electrostatics
Concept: Dielectrics and Polarisation
[1]6.4

In potentiometer experiment, if l1 is the balancing length for e.m.f. of cell of internal resistance r and l2 is the balancing length for its terminal potential difference when shunted with resistance R then :

(a) `l_1=l_2((R+r)/R)`

(b) `l_1=l_2((R)/(R+r))`

(c) `l_1=l_2((R)/(R-r))`

(d) `l_1=l_2((R-r)/R)`

Chapter: [13] Current Electricity
Concept: Metre Bridge
[1]6.5

The energy of photon of wavelength X is_____ .

[h = Planck’s constant, c = speed of light in vacuum]

(a)hcλ

(b)hλ/c

(c)λ/hc

(d)hc/λ

 

Chapter: [17] Electrons and Photons
Concept: Einstein’s Equation - Particle Nature of Light
[1]6.6

Which logic gate corresponds to the truth table given below?

A

B

Y

0

0

I

0

1

0

1

0

0

1

1

0

 

(a)  AND

(b)  NOR

(c)  OR  

(d) NAND

Chapter: [19] Semiconductors
Concept: Digital Electronics and Logic Gates
[1]6.7

The process of superimposing a low frequency signal on a high frequency wave is_______ .

(a) detection  

(b)  mixing

(c) modulation            

(d) attenuation

Chapter: [20] Communication Systems
Concept: Modulation and Its Necessity
[7]7 | Attempt any one of the following :
[7]7.1

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 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

A conductor of any shape, having area 40 cm2 placed in air is uniformly charged with a charge 0* 2µC. Determine the electric intensity at a point just outside its surface. Also, find the mechanical force per unit area of the charged conductor.

[∈0=8.85x10-12 S.I. units]

Chapter: [12] Electrostatics
Concept: Mechanical Force on Unit Area of a Charged Conductor
[7]7.2

With the help of a neat labelled diagram, describe the Geiger- Marsden experiment

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

What is mass defect?

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Mass-Energy Relation and Mass Defect

The photoelectric work function for a metal surface is 2.3 eV. If the light of wavelength 6800A is incident on the surface of metal, find threshold frequency and incident frequency. Will there be an emission of photoelectrons or not?

[Velocity of light c = 3 x 108 m/s,

Planck’s constant, h = 6.63 * 10-34 Js ]

Chapter: [17] Electrons and Photons
Concept: Photoelectric Effect - Hertz’S Observations
[9]8 | Attempt any three :
[3]8.1

Determine the change in wavelength of light during its passage from air to glass. If the refractive index of glass with respect to air is 1.5 and the frequency of light is 3.5 x 1014 Hz, find the wave number of light in glass.

[Velocity of light in air c = 3 x 108 m/s]

Chapter: [10] Wave Theory of Light
Concept: Reflection and Refraction of Plane Wave at a Plane Surface Using Wave Fronts
[3]8.2

In biprism experiment, 10th dark band is observed at 2.09 mm from the central bright point on the screen with red light of wavelength 6400 A. By how much will fringe width change if blue light of wavelength 4800A is used with the same setting?

Chapter: [11] Interference and Diffraction
Concept: Measurement of Wavelength by Biprism Experiment
[3]8.3

Describe Kelvin’s method to determine the resistance of galvanometer by using metre bridge.

Chapter: [13] Current Electricity
Concept: Meter Bridge
[3]8.4

Explain the elementary idea of an oscillator with the help of block diagram

Chapter: [19] Semiconductors
Concept: Oscillators
S