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

SubjectPhysics
Year2015 - 2016 (July)

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

The difference in tensions in the string at lowest and highest points in the path of the particle of mass 'm' performing vertical circular motion is:....

a) 2 mg

b) 4 mg

c) 6 mg

d) 8 mg

Chapter: [1] Circular Motion
Concept: Vertical Circular Motion Due to Earth’s Gravitation
[1]1.2

The body is rotating with uniform angular velocity (w) having rotational kinetic energy (E). Its angular momentum (L) is: ...............

a) (2E)/ω

b) E^2/ω

c) E/ω^2

d) E/(2ω)

Chapter: [3] Angular Momentum
Concept: Definition of M.I., K.E. of Rotating Body
[1]1.3

The S.I. unit of compressibility is..........

a) m^2/n

b) Nm^2

c) N/m^2

d) (kg)/m^3

Chapter: [5] Elasticity
Concept: Applications of Elastic Behaviour of Materials
[1]1.4

The working of RADAR is based on ...............

a) resonance

b) speed of a star

c) Doppler effect

d) speed of rotation of sun

Chapter: [7] Wave Motion
Concept: Beats

The working of RADAR is based on ...............

a) resonance

b) speed of a star

c) Doppler effect

d) speed of rotation of sun

Chapter: [10] Wave Theory of Light
Concept: Beats
[1]1.5

If two capillary tubes of different diameters are partially dipped in the same liquid vertically, then the rise of liquid ..........

a) is same in both the tubes

b) is more in the tube of larger ~iameter

c) will not be in smaller diameter tube

d) is more in the tube of smaller diameter

Chapter: [6] Surface Tension
Concept: Capillarity and Capillary Action
[1]1.6

A sonometer wire vibrates with three nodes and two antinodes, the corresponding mode of vibration is ...................

a) First overtone

b) Second overtone

c) Third overtane

d) Fourth overtone

Chapter: [8] Stationary Waves
Concept: Free and Forced Vibrations
[1]1.7

Two gases exert pressure in the ratio 3: 2 and their densities are in the ratio 2: 3, then the ratio of their R.M.S. velocities is ...........

(a) 2:3

(b) 3:2

(c) 2:1

(d) 1:2

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Derivation for Pressure of a Gas
[12]2 | Attempt any SIX
[2]2.1

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

Chapter: [1] Circular Motion
[2]2.2

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]2.3

Draw a neat labelled diagram of rise of liquid in capillary tube showing different components of tension (force).

Chapter: [6] Surface Tension
Concept: Capillarity and Capillary Action
[2]2.4

State any four assumptions of kinetic theory of gases.

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Kinetic Theory of Gases- Assumptions
[2]2.5

A tube open at both ends has length 47 em. Calculate the fundamental frequency of air column. (Neglect end correction. Speed of sound in air is 3.3 x 102m/s}

Chapter: [8] Stationary Waves
Concept: Study of Vibrations of Air Columns
[2]2.6

A uniform solid sphere has a radius 0.1 m and density 6 x 103 kg/m3• Find its moment of inertia about a tangent to its surface.

Chapter: [3] Angular Momentum
Concept: Physical Significance of M.I (Moment of Inertia)
[2]2.7

A particle executes S.H.M. with a period of 10 seconds. Find the time in which its potential energy will be half of its total energy.

Chapter: [4] Oscillations
Concept: Simple Harmonic Motion
[2]2.8

A stone of mass 2 kg is whirled in a horizontal circle attached at the end of 1.5m long string. If the string makes an angle of 30° with vertical, compute its period. (g = 9.8 m/s2)

Chapter: [3] Angular Momentum
Concept: Rolling Motion
[9]3 | Attempt any THREE
[3]3.1

State Kepler's laws of planetary motion.

Chapter: [2] Gravitation
Concept: Kepler’S Laws
[3]3.2

Obtain an expression for torque acting on a body rotating with uniform angular acceleration.

Chapter: [1] Circular Motion
Concept: Angular Acceleration
[3]3.3

A steel wire having cross-sectional area 2 mm2 is stretched by ION. Find the lateral strain produced in the wire. (Given : Y for steel = 2 x 1011 N / m2, Poisson's ratio δ = 0.29)

Chapter: [5] Elasticity
Concept: Definition of Stress and Strain
[3]3.4

A body cools from 62°C to 54°C in 10 minutes and to 48°C in the next 10 minutes. Find the temperature of the surroundings.

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Temperature and Heat
[7]4 | Attempt Any One
[4]4.1

Explain the formation of stationary wave by analytical method. Show that nodes and antinodes are equally spaced in a stationary wave.

Chapter: [8] Stationary Waves
Concept: Formation of Stationary Waves on String
[3]4.2

The speed limit for a vehicle on road is 120 km/ hr. A policeman detects a drop of 10% in the pitch of horn of a car as it passes him. Is the policeman justified in punishing the car driver for crossing the speed limit? (Given: Velocity of sound= 340 m/s)

Chapter: [1] Circular Motion
Concept: Equation for Velocity and Energy at Different Positions of Vertical Circular Motion
[4]4.3

Define practical simple pendulum

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

Show that motion of bob of the pendulum with small amplitude is linear S.H.M. Hence obtain an expression for its period. What are the factors on which its period depends?

Chapter: [4] Oscillations
Concept: Some Systems Executing Simple Harmonic Motion
[3]4.4

The total free surface energy of a liquid drop is pisqrt2 times the surface tension of the liquid. Calculate the diameter of the drop in S.l. unit.

Chapter: [6] Surface Tension
Concept: Surface Tension
[7]5 | Select and write the most appropriate answer from the given alternatives for each sub-question
[1]5.1

A parallel beam of light travelling in water is incident obliquely on a glass surface. After refraction its width ..............

a) decreases

b) increases

c) remains the same

d) becomes zero

Chapter: [11] Interference and Diffraction
Concept: Interference of Light
[1]5.2

If 'a' is the aperture of telescope and A. is the wavelength of light then resolving power of telescope is .............

a) lambda/(1.22a)

b) (1.22a)/lambda

c) (1.22 lambda)/a

d) a/(1.22lambda)

Chapter: [11] Interference and Diffraction
Concept: Resolving Power of a Microscope and Telescope
[1]5.3

From earth's surface, ionospheric layer of atmosphere lies between ............

(a) 12 km to 50 km

(b) 50 km to 80 km

(c) 80 km to 400 km

(d) 400 km to 700 km

Chapter: [20] Communication Systems
Concept: Space Communication
[1]5.4

The kinetic energy of emitted photoelectorns is independent of ............

(d) collector plate potential

Chapter: [3] Angular Momentum
Concept: Definition of M.I., K.E. of Rotating Body
[1]5.5

In hydrogen atom Balmer series is obtained when the electron jumps from ............ .

(a) higher orbit to first orbit

(b) first orbit to a higher orbit

(c) higher orbit to the second orbit

(d) second orbit to a higher orbit

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Wavelength of an Electron
[1]5.6

The fraction of the total current passing through the galvanometer is ............ .

a) S/(S+G)

b) G/(S+G)

c) (S+G)/G

d) (S+G)/S

Chapter: [14] Magnetic Effects of Electric Current
Concept: Moving Coil Galvanometer
[1]5.7

A meter gauge train is heading north with speed 54 km/hr in earth's magnetic field 3 x 10-4T. The e.m.f. induced across the axle joining the wheels is ..........

(a) 0.45 mV

(b) 4.5 mV

(c) 45 mV

(d) 450 m V

Chapter: [15] Magnetism
Concept: Magnetic Properties of Materials
[12]6 | Attempt any SIX
[2]6.1

Distinguish between intrinsic and extrinsic semiconductor. (Give any two points).

Chapter: [19] Semiconductors
Concept: Extrinsic Semiconductor
[2]6.2

Draw the block diagram of a receiver in communication system

Chapter: [20] Communication Systems
Concept: Elements of a Communication System
[2]6.3

A point is situated at 6.5 em and 6.65 em from two coherent sources. Find the nature of illumination at the point, if wavelength of light is 5000 Å

Chapter: [10] Wave Theory of Light
Concept: Wave Theory of Light
[2]6.4

Draw the diagrams showing the dipole moments in paramagnetic substance when external magnetic field is (a) absent (b) strong

Chapter: [15] Magnetism
Concept: Magnetic Dipole Moment of a Revolving Electron
[2]6.5

A voltmeter has a resistance of 100 Ω. What will be its reading when it is connected across a cell of e.m.f. 2V and internal resistance 20Ω?

Chapter: [14] Magnetic Effects of Electric Current
Concept: Moving Coil Galvanometer
[2]6.6

The susceptibility of magnesium at 300K is 1.2 x 10-5. At what temperature will the susceptibility increase to 1.8 X 10-5?

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Temperature and Heat
[2]6.7

What is de Broglie wavelength of an electron accelerated through 25000 volt?

Chapter: [18] Atoms, Molecules and Nuclei
Concept: Wavelength of an Electron
[2]6.8

Draw the schematic symbols for AND, OR, NOT and NAND gate

Chapter: [19] Semiconductors
Concept: Digital Electronics and Logic Gates
[9]7 | Attempt any THREE:
[3]7.1

Using analytical method for interference bands, obtain an expression for path difference between two light waves.

Chapter: [10] Wave Theory of Light
Concept: Wave Theory of Light
[3]7.2

State the law of radioactive decay.

Chapter: [18] Atoms, Molecules and Nuclei

Derive the mathematical expression for law of radioactive decay for a sample of a radioactive nucleus

Chapter: [18] Atoms, Molecules and Nuclei

Represent Radioactive Decay curve using relation N = N_o e^(-lambdat) graphically

Chapter: [18] Atoms, Molecules and Nuclei
[3]7.3

Determine the change in wavelenght of light during its passage from air to glass, if the refracrtive index of glass with respect to air is 1.5 and the frequency of light is 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: Wave Theory of Light
[3]7.4

Light of wavelength 3000Å falls on a metal surface having work function 2.3 eV. Calculate the maximum velocity of ejected electrons

(Planck's constant h = 6.63 x 10-34 J.s., Velocity of light c = 3 x 108 m/s, mass of an electron = 9.1 x 10-31 kg)

Chapter: [10] Wave Theory of Light
Concept: Wave Theory of Light
[7]8 | Attempt Any One
[1]8.1

What is electromagnetic induction?

Chapter: [16] Electromagnetic Inductions
Concept: Electromagnetic Induction
[4]8.2

Prove theoretically  (electromagnetic induction) e = (dphi)/(dt)

Chapter: [16] Electromagnetic Inductions
Concept: Electromagnetic Induction
[2]8.3

A potentiometer wire has length of 2m and resistance 10Ω. It is connected in series with resistance 990Ω and a cell of e.m.f. 2V. Calculate the potential gradient along the wire.

Chapter: [13] Current Electricity
Concept: Meter Bridge
[4]8.4

With the help of a neat diagram, describe the construction and working of van de Graff generator.

Chapter: [12] Electrostatics
Concept: Van-deGraaff Generator
[3]8.5

A moving coil galvanometer has a resistance of 25Ω and gives a full scale deflection for a current of 10mA. How will you convert it into a voltmeter having range 0 - 100 V?

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