Ahsec Class 12 Physics Solved Question Paper - 2026| ASSEB BOARD
2026
PHYSICS
(Theory)
Full Marks: 70
Pass Marks: 21
Time: 3 hours
The figures in the
margin indicate full marks for the questions
1. Answer any eight questions from the following as directed: 1×8=8
(a) Mention any one of the basic
properties of electric charge. 1
Ans:-Fundamental property of electric
charge:- Electric
charge is quantized (i.e., the total charge of an object is an integral
multiple of the elementary charge of an electron, q = ne).
(Alternatively: Electric charge is conserved, or charge is additive.)
(b) Give two examples of polar
molecules. 1/2x2=1
Ans:- Two examples of polar
molecules:-
(i) Water (H2O)
(ii) Hydrogen chloride (HCl)
(c) To drive a device of power P and
voltage V, the power wastage in the connecting wire is proportional to
(i) V2
(ii) 1/V2 (Choose the
correct one) 1
Ans:- (ii)
1/V2
(d) What is the potential difference
between A and B in the circuit? 1
(e) What do you mean by current
sensitivity of a galvanometer? 1
Ans:- The current sensitivity of a
galvanometer is defined as the deflection produced in the galvanometer per unit
of current flowing through its coil.
(f) The phenomenon of perfect
diamagnetism in superconductor is called Meissner
effect (or Meissner-Ochsenfeld effect). (Fill up the gap) 1
(g) At resonant frequency, the total
impedance of a series L-C-R circuit is minimum
and equal to its pure resistance (R). (Fill up the gap) 1
(h) A bar magnet is brought near a
coil as shown in the figure. What would be the direction of induced current in
the coil, if you look at the coil from the side of the magnet? 1
Ans:- Direction of the induced current:
Anti-clockwise (i.e., opposite to the direction of the hands of a clock).
Reason: As the North (N) pole of the bar magnet approaches the coil, according
to Lenz's Law, the end of the coil facing the magnet develops North polarity to
oppose its motion. When viewed from the side of the magnet, North polarity
corresponds to an anti-clockwise current.
(i) The critical angles for glass (μg
= 1.5 ), water (μw =1.33) and diamond (μD = 2.42 ) are θg, θw and θD respectively. Arrange the angles in descending order. 1
(j) Write the dimensional formula for
(k) What is the shape of the
wavefront diverging from a point source? 1
Ans:- Shape of the wavefront: Spherical
(spreading out from a point source).
(l) What is the name of light
particle? What physical quantity determines the energy of a light particle?
1/2+1/2=1
(m) In Rutherford's α-scattering experiment, for what value of scattering angle,
the impact parameter becomes minimum? 1
Ans:- Scattering angle for the minimum
impact parameter in Rutherford's experiment: 180° (back-scattering).
(n) Write a difference between
nuclear fission and nuclear fusion. 1
Ans:- Difference between nuclear
fission and nuclear fusion are:- In nuclear fission, a heavy nucleus splits into two or more
smaller nuclei. In nuclear fusion, two or more light nuclei combine to form a
heavier nucleus.
(0) In extrinsic semiconductor doped
with pentavalent impurity Electrons
become majority carriers and holes the
minority carriers. (Fill up the gaps) 1/2+1/2=1
2. Answer
any ten questions from the following: 2×10 = 20
(a) Write Coulomb's law in vector
form and define 1 coulomb charge. 1+1=2
(b) A comb running through one's dry
hair attracts small bits of paper. Why? What happens if the hair is wet? 1+1=2
Ans:- Combing dry hair vs. wet hair:-
Why it attracts pieces of paper:-
Combing dry hair generates friction,
causing an exchange of electrons between the hair and the comb, which results
in the comb acquiring an electric charge. This charged comb induces an opposite
charge on the small, neutral pieces of paper, causing them to be attracted to
the comb due to electrostatic force.
What happens if the hair is wet:-
If the hair is wet, water acts as a
conductor. Any charge generated by friction immediately dissipates into the
ground through the moisture and the user's body. Consequently, a static charge
cannot build up or remain on the comb, and it fails to attract the pieces of
paper.
(c) Plot a graph showing the
variation of current with voltage for the material GaAs. On the graph, mark the
region where (i) resistance is negative and (ii) Ohm's law is obeyed.
1+1/2+1/2=2
Ans:- I-V characteristics for Gallium
Arsenide (GaAs):-
Description:-
For GaAs (which exhibits the
transferred electron effect, similar to a Gunn diode), the graph of current (I)
versus voltage (V) is non-linear (not a straight line):-
(i) Region of negative resistance: The region beyond the peak threshold
voltage where current decreases as voltage increases (negative slope on the I-V
curve).
(ii) Region where Ohm's Law applies: The initial linear region starting
from the origin (V=0), where current is directly proportional to voltage
(constant positive slope/resistance).
(d) The resistance of a wire of
length 15 m and uniform cross-section 6.0×10-7 m2 is
measured to be 5.0Ω. What is the resistivity of the
material of the wire? 2
(e) Two long and parallel conductors
A and B are carrying currents 8.0 A and 5.0 A in the same direction. A and B
are separated by a distance of 4.0 cm. Calculate the force on a length of 1 cm
of wire A. 2
(f) What is magnetic susceptibility
x? Of two metals P and Q, it is found that xp >> 1 and −1≤ xQ <0. Name the types of
material to which metals P and Q belong. 1+1/2+1/2=2
(g) A square loop of side 10 cm and
resistance 0.5 Ω is placed
vertically in the east-west plane. A uniform magnetic field of 0.10 T is set up
across the plane in the north-east direction. The magnetic field is decreased
to zero in 0.7 s at steady rate. Determine the magnitude of the induced e.m.f.
2
(h) A 15.0 µF capacitor is connected to a 220
V, 50 Hz source. Find the capacitive reactance in the circuit. 2
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