Physics 2015-2016 HSC Science (Electronics) 12th Standard Board Exam Question Paper Solution

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

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

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

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

Define emissive power and coefficient of emmision of a body.

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]

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

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?

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.

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..........

vt

(v/D)-t

vt/2D

2vt/D

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......

W₁=W₂

W₁<W₂

W₁>W₂

W₁=W₂=0

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 .....

four times that of A.

two times that of A.

three times that of A.

same as that of A.

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

0 rad

`π/4`  rad

`π/2` rad 

π rad

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 .........

`n_1sqrt((sigma+1)/sigma)`

`n_1sqrt((sigma-1)/sigma)`

`n_1sqrt(sigma/(sigma+1))`

`n_1sqrt(sigma/(sigma-1))`

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

`(1+f)/(2+f)`

 `(2+f)/(3+f)`

 `(4+f)/(3+f)`

`(5+f)/(4+f)`

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 ......

5 m/s

4 m/s

3 m/s

2 m/s

Define linear S.H.M.

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

Explain analytically how the stationary waves are formed

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

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 42^nd tuning fork

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 ]

State the theorem of parallel axes about moment of inertia.

Prove the theorem of parallel axes about moment of inertia

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

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.

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

What is 'diffraction of light'

Explain two types of diffraction of light.

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

Distinguish between ‘paramagnetic’ and ‘ferromagnetic’ substances.

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

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

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?

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

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

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

`1/sqrt3`

`sqrt(3/2)`

1

`sqrt3` 

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

length of the telescope

focal length of an objective

diameter of an objective

focal length of an eyepiece

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

increase in charge on sphere.

increase in dielectric constant.

decrease in the distance from the centre of sphere.

decrease in square of distance from the centre of sphere.

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 :

`l_1=l_2((R+r)/R)`

`l_1=l_2((R)/(R+r))`

`l_1=l_2((R)/(R-r))`

`l_1=l_2((R-r)/R)`

The energy of photon of wavelength X is_____ .

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

hcλ

`(hλ)/c`

`λ/(hc)`

`(hc)/λ`

Which logic gate corresponds to the truth table given below?

AND

NOR

OR

NAND

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

detection  

mixing

modulation 

attenuation

State the principle on  which transformer works.

Explain transformer working with construction.

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

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]

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

What is 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 ]

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]

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?

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

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