AHSEC| CLASS 12| PHYSICS| SOLVED PAPER - 2024| H.S. 2ND YEAR
2024
PHYSICS
(Theory)
Full Marks: 70
Pass Marks: 21
Time: Three hours
The figures in the margin indicate
full marks for the question.
1. Answer any eight questions from the following as directed: 1x8=8
(a) The
process of sharing charges with the earth is called earthing.
(b) What is
the unit of mobility?
Ans:- The
unit of mobility is m²/V s (square meter per volt-second).
(c) Magnetic
field lines are also called magnetic lines of force. (State true or false)
(d) Find the
magnitude of current induced in a coil of resistance 2Ω if the
e.m.f induced there is 3.8x10-3V.
(e) What
is the general feature of electromagnetic waves?
Ans:- The
general characteristic of electromagnetic waves is that they can propagate in
vacuum and can travel at the speed of light.
(f) If the
critical angle of water with respect to air is 48.75 and sin 48.75=0.75, cos
48.75=0.65 and tan 48.75=1.14 approximately, what will be the refractive index
of water?
(g) For a
given frequency of incident radiation photoelectric
effect is independent of its
intensity. (Fill in the blanks)
(h) In a-particle
scattering experiment for (i) small, and (ii) large impact parameters the
scattering angles are approximately equal to 180∘ and 0∘. (Fill in the blanks)
(i) If x
equals one atomic mass number (u), then express y in a.m.u.(u).
Ans:- If x is
equal to an atomic mass number (u), then y expressed in a.m.u. (u) is also 1
a.m.u.
(j) Write
the full forms of (i) LCD, and (ii) CRT.
Ans:- The
full forms are:
(i) LCD: Liquid
Crystal Display
(ii) CRT: Cathode
Ray Tube
(k) If the
current flowing through a coil of N number of turns and cross-sectional area A
be I, what will be its magnetic moment?
Ans:- If the
current flowing through a coil having N turns and cross-sectional area A is I,
then its magnetic moment m is given by: m=NIA.
(l) Write
the expressions for equivalent capacitances if the capacitors C1 and
C2 are connected in (i) series, and (ii) parallel.
(m)
Mention the principle on which a transformer works.
Ans:- The
principle on which the transformer works is electromagnetic induction.
2. Answer the following questions as directed: 2x10=20
(a)
Classify the following into (i) polar, and (ii) non-polar molecules: CO2,
HCl, H2 and H2O.
Ans:- To
classify given molecules into polar and nonpolar categories, we need to
consider their molecular geometry and the electronegativities of the atoms
involved.
(i) Polar
Molecules
(a) HCl
(Hydrochloric Acid): HCl is polar because of the significant difference
in electronegativities between hydrogen (H) and chlorine (Cl), resulting in a
dipole moment.
(b) H2O
(Water): Water is also a polar molecule. It has a bent molecular geometry,
and the difference in electronegativities between hydrogen and oxygen creates a
dipole moment.
(ii)
Nonpolar Molecules
(a) CO2
(Carbon Dioxide): CO2 is nonpolar despite having a polar bond
(C=O). Its linear geometry causes the dipole moments to cancel each other out.
(b) H2
(Hydrogen gas): H2 is non-polar as it has two identical hydrogen atoms sharing
electrons equally, resulting in no dipole moment.
Summary:-
(i) Polar:
HCl, H2O
(ii)
Non-polar: CO2, H2
Or
Calculate the flux passing through a circular area of radius 5cm placed perpendicular to a uniform electric field
(b) “Inside a
conductor, electrostatic field is zero.” Explain.
Ans:- Inside a
conductor, the electrostatic field is zero because of the behaviour of free
electrons in response to external electric fields. When a conductor is placed
in an electric field, the free electrons within the conductor move in such a
way that they redistribute themselves over the surface. This motion continues
until they reach a state of electrostatic equilibrium, where the internal
electric field cancels out any external influence.
Explanation:-
(i) Charge
redistribution: In a conductor, the free electrons can move around easily. When
an external electric field is applied, these electrons shift to one side of the
conductor, causing the charge to separate. This results in the accumulation of
a negative charge on one surface and an equal positive charge on the opposite
surface.
(ii) State of
equilibrium: In electrostatic equilibrium, the forces acting on these free
electrons are balanced. If an electric field were present inside the conductor,
it would exert a force on the electrons, causing them to move. However, in
equilibrium, there is no net force acting on the electrons; Thus, they do not
move, and the electric field inside the conductor remains zero.
(iii) Gauss's
Law: This phenomenon can also be understood through Gauss's law, which
states that the electric flux passing through a closed surface is proportional
to the charge enclosed. Since there is no charge inside a conductor (all the
excess charge remains on its surface), the electric field inside must be zero.
In short, the
electrostatic field inside a conductor is zero because any external electric
field induces charge separation which cancels any internal electric field,
leading to a state of equilibrium where no net force acts on the charges within
the conductor.
Or
A 12pF capacitor
is connected to a 50V battery. How much electrostatic energy is stored in the
capacitor?
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