# Class 10 Physics 2021 Solved Past Paper Overseas Federal Board

## Class 10 Physics 2021 Solved Paper Overseas

Federal Board FBISE Class 10 Physics 2021 Solved Past Paper Overseas is solved for you in this post. For more Class 10 Solved Papers visit our Class 10 Solved Papers Page.

### Section A

#### Q1. MCQs

Class-10-Physics-2021-O-MCQs

### Class 10 Physics 2021 OverseasSection B

#### Q2.

##### (i) Furnish three examples of motion in everyday life, which are Simple Harmonic.

Ans. Following are the three examples of motion in everyday life, which are Simple Harmonic:
1. A girl swinging on a swing.
2. Pendulum used in wall clocks.
3. Vibration of strings in musical instruments
5. Sea-saw
6. Human eardrum

##### (ii) What is the wavelength of the radio waves transmitted by an FM station at 90MHz where 1M=106 and the speed of radio waves is 3 x 108 ms-1.

Sol.  Frequency = f = 90 MHz = 90 x 106 Hz
Speed of the waves = v = 3 x 108 m s-1
Wavelength = λ =?

Using wave equation
v = f λ
Or λ = v / f
λ = 3 × 108 / 90 × 106
λ = 3.33 m

##### (iii) What is meant by the term “intensity level of sound”? Name and define the unit of the intensity level of sound.

Ans. Intensity Level of Sound
The difference between the loudness of the faintest audible sound and the loudness of an unknown sound is called the intensity level or sound level of the unknown sound.

The unit of the intensity level of sound is called bel. Since bel is a very large unit of the intensity level of a sound, therefore, a smaller unit called decibel is used. Decibel is abbreviated as dB and 1 bel is equal to 10 dB.

The intensity level of sound is 1 Bel if the intensity of the sound is 10 times greater than the intensity of the faintest audible sound.

##### (iv) If the pitch of the sound is increased, what are the changes in the following?a. The frequency                                 b. The wavelengthc. The amplitude of the wave

Ans. a. Frequency: If the pitch of the sound is increased, its frequency is also increased because:
Frequency ∝ Pitch
b. Wavelength: If the pitch of the sound is increased, its wavelength is decreased because:
Wavelength ∝ 1 / Pitch
c. The Amplitude of the Wave: If the pitch of the sound is increased, the amplitude of the wave does not change because amplitude does not depend on the pitch.

##### (vii) Is Electric Intensity a vector quantity? What will be its direction?

Ans.    Yes, electric intensity is a vector quantity and is defined as the force acting on the unit positive charge placed inside an electric field.
Its direction is that in which a unit positive charge moves inside an electric field.

### Class 10 Physics 2021 OverseasSection C

#### Q3.

##### (i) What is meant by resistance? Write its SI unit.

Ans. Resistance: The property of a substance that offers opposition to the flow of current through it is called its resistance. This opposition comes from the collisions of moving electrons with atoms of the substance.
The SI unit of resistance is Ohm denoted by the symbol Ω.

##### (iii) A magnetic field is produced around a straight current-carrying conductor. How can this be demonstrated by an experiment?

Ans. EXPERIMENT
To demonstrate this, we take a straight conductor wire and pass it vertically through cardboard. Now connect the two ends of the conductor wire with the terminals of the battery so that current flows through the circuit in the clockwise direction. The lines of force of the magnetic field produced around the wire would be in the form of concentric circles. If we place a compass needle at different points in the region of the magnetic field, it will align along the direction of the magnetic field. Also if we sprinkle some iron filings on the cardboard around the wire, they will align themselves in concentric circles in the clockwise direction.

If we reverse the direction of the current by reversing the terminals of the battery, the compass needle also reverses its direction. Now the magnetic field lines will align in the anticlockwise direction.

##### (v) Differentiate between analogue electronics and digital electronics. Write down the names of three analogue and three digital devices that are commonly used in everyday life.

Ans. Analogue Electronics: The branch of electronics consisting of circuits which process analogue quantities is called analogue electronics.
Digital Electronics: The quantities whose values vary in a non-continuous manner are called digital quantities.
Examples of analogue devices are loudspeakers, old CRT TV, Land Line Telephones and Audio Tape etc.
Examples of digital devices are mobile phones, Laptops Computers, and LED TVs, etc

##### (vi) Determine which of these radioactive decay processes are possible:(a) 90Th230→88Ra226 + 2He4(b) 84Po214→82Pb208 + 2He4(c) 6C12→7N14 + -1β0

Ans. (a) 90Th230 88Ra226 + 2He4
The above process is possible because values of A and Z are correct on both sides.

(b) 84Po214 82Pb208 + 2He4
The above process is not possible because value of A (atomic mass) on Pb is incorrect (should be 210 instead of 208).

(c) 6C12 7N14 + -1β0
The above process is not possible because value of A (atomic mass) should not change during emission of β particle.

##### (v) The half-life of 7N14 is 7.3s. A sample of this nuclide of Nitrogen is observed for 29.2s. Calculate the fraction of the original radioactive isotope remaining after this time.

Sol. Half-life of 7N14 = 7.3s
Observation time = 29.2s
We know that after helf-life, the fraction of original radioactive isotope left = 1/2
So,
Fraction left after 7.3s (1st half-life) = 1/2
Fraction left after 2×7.3s = 14.6s (2 half-lives) = 1/2 (1/2) = 1/4
Fraction left after 3 × 7.3s = 21.9s (3 half-lives) = 1/2 (1/4) = 1/8
Fraction left after 4 × 7.3s = 29.2s (4 half-lives) = 1/2 (1/8) = 1/16

Thus, the fraction of the original radioactive isotope remaining after 29.2s will be 1/16.