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ICSE-X-Physics

Previous Year Paper year:2018

with Solutions - page 3

#3

#3-a [2]
Displacement distance graph of two sound waves A and B, travelling in a
medium, are as shown in the diagram below.

Study the two sound waves and compare their:

#3-a-i
Amplitudes
Ans : Amplitude of Wave A is ``\pu{20 cm}``. Amplitude of Wave B is ``\pu{10 cm}``.

#3-a-ii
Wavelengths
Ans : Wavelength of B is twice the wavelength of A.

#3-b [2]
You have three resistors of values ``2\Omega``, ``3\Omega`` and ``5\Omega``. How will you join them so
that the total resistance is more than ``7\Omega``?

#3-b-i
Draw a diagram for the arrangement.
Ans :

#3-b-ii
Calculate the equivalent resistance.
Ans : We have to connect them in a series to get equivalent resistance:
2 ``\Omega`` + 3 ``\Omega`` + 5 ``\Omega`` = 10 ``\Omega``

#3-c [2]

#3-c-i
What do you understand by the term nuclear fusion?
Ans : Nuclear fusion is the process in which two light nuclei combine to form a
heavy nucleus. In this process, a huge amount of energy is released.

#3-c-ii
Nuclear power plants use nuclear fission reaction to produce electricity.
What is the advantage of producing electricity by fusion reaction?

Ans :
For the same mass, the energy released in a fusion process is more than
that released in a fission process. A fusionable substance is found in
abundance. These substances are not radioactive and do not give any
harmful radiation. Disposal of waste is not difficult.

#3-d [2]

#3-d-i
What do you understand by free vibrations of a body?
Ans : Periodic vibrations of the body in the absence of any external force on it
are called natural or free vibrations.

#3-d-ii
Why does the amplitude of a vibrating body continuously decrease during
damped vibrations?
Ans : The amplitude of a vibrating body continuously decreases during damped
vibration because of the frictional or resistive force due to the
surrounding.

#3-e [2]

#3-e-i
How is the e.m.f. across primary and secondary coils of a transformer
related with the number of turns of coil in them?
Ans : $$ \frac {\text{Number of turns in secondary coil}} {\textrm{Number of turns in primary coil}} $$
$$= \frac {\text{emf across secondary coil}} {\textrm{emf across primary coil }} $$