# Physics 10 Solved Paper 2017 Federal Board

## Physics 10 Solved Paper 2017

Past papers always play a vital role in exam preparations. By consulting past papers, a student comes to know about the paper pattern of his forthcoming exam. We have produced the Federal Board Physics 10 Solved Paper 2017 in this post. You can see the more fbise solved past papers of class 10 on our website.

## Physics 10 Solved Paper 2017

### Physics 10 Solved Paper 2017Section B

#### Q2.

##### (i) What is the wavelength of the Radio-waves transmitted by an FM station at 90 MHz? The speed of the Radio-wave is 3´108 m/s.

Sol.  Frequency = f = 90 MHz = 90 × 106 Hz

Speed of the waves = v = 3 × 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

##### (ii) Give any three uses of Ultrasound.

Ans. Uses of Ultrasound
1.  Ultrasonic waves are used for the diagnosis and treatment of many diseases.
2.  Powerful ultrasonic is being used to remove blood clots from the arteries.
3.  These waves are used to determine the depth of the sea bed and to find the location of an object by its echo under the seawater.

##### (iii) An object 30cm tall is located 10.5cm from a Concave Mirror with Focal Length 16cm. Where is the image located?

Sol.  Height of object = hi = 30 cm
Distance of object = p = 10.5 cm
Focal length = f = 16 cm
Distance of image = q =?
Using mirror formula

##### (iv) Why a fish under water appears to be at a different depth below the surface than it actually is?

Excluded from the Syllabus

##### (v)  Write down the function of a Thermister.

Ans.  A thermistor is a heat-sensitive resistor. Its resistance decreases (current increases) as it gets hotter. This is because, on heating, more free electrons become available for the conduction of current.

##### (vi) How Lenz’s law can be used for finding the direction of induced e.m.f?

Ans.  Lenz’s law states that the direction of induced current in a circuit is always such that it opposes the cause that produces it.
Hence this law can be used for finding the direction of induced emf. Since the direction of induced current in a circuit is always opposite to its cause of production, therefore, can find it by knowing the direction of the cause of emf production.

##### (vii)   Briefly describe the process of Thermionic Emission from a metal surface.

Ans.  When metals are heated, electrons are emitted from the surface of metals. The process of emission of electrons from the surfaces of hot metals is called thermionic emission.

##### (viii) What do you understand by information and communication technology?

Excluded from the Syllabus

##### (ix)  Which has more penetrating power, an alpha particle or a gamma-ray photon? How?

The gamma-ray photon has more penetrating power and can penetrate a considerable thickness of concrete. It is due to its large speed and neutral nature. While alpha particle has the shortest range because of its strong interacting or ionizing power.

##### (x)   If Tritium is decayed by emitting an electron. What will be the daughter nucleus?

Excluded from the Syllabus

##### (xi)    Define the relationship between the critical angle and the refractive index of a substance.

Ans. The relationship between the critical angle (C) and the refractive index (n) can be defined by the following formula:
sin C = 1/n
or Critical angle = sin-1 (1/n)
We can also say that the product of the sine of critical angle and refractive index is always equals to 1. i.e.
(sin C ) (n) = 1

##### (xii)  What is a NOR Gate? Draw its truth table and symbol.

Ans. NOR Gate: The combination of OR gate with NOT gate (at the output) is called NOR gate. In NOR gate the output of OR gate is inverted. The bubble in the symbol of NOR gate shows that the output of OR gate is inverted.

##### (xiii)  Write down the harmful effects of Radiation Hazard.

1. Radiation burns, mainly due to beta and gamma radiations, which may cause redness and sores on the skin.
2. Genetic mutations in both humans and plants. Some children are born with serious deformities.

##### (xiv)   How is an electroscope used for identifying a conductor and an insulator?

Excluded from the Syllabus

### Physics 10 Solved Paper 2017Section C

#### Attempt any two (02) questions.

##### Q3 a. What is simple microscope? Also discuss Magnifying Power of Simple Microscope.  (02+04)

Excluded from the Syllabus

##### Q4 a.  What is Transformer? How does it work?  (02+04)

Ans. TRANSFORMER
A transformer is an electrical device used to increase and decrease the value of alternating voltage. It works in accordance with the principle of mutual induction.
It consists of two coils, which are wound on the opposite sides of a rectangular iron core. One coil to which an alternating voltage is supplied is called the primary coil and the other coil in which alternating voltage is induced is called the secondary coil. The value of the induced alternating voltage or output voltage (Vs) depends upon the number of turns of the primary coil (Np) and the number of turns of the secondary coil (Ns). These are related by the following expression:
Vs / Vp = Ns / Np
Where (Vp) is the input voltage supplied at the primary coil.

##### b.  Cobalt-60 is a radioactive element with a Half-Life of 5.25 years. What fraction of the original sample will be left after 26 years?   (04)

Solution:
Half life of Cobalt-60 = T½ = 5.25 Years
Time of decay = T = 26 Years
Fraction of original sample left = N / No =?

Hence fraction of the original sample left after 26 years = 1/32

##### Q5 a.  Discuss motion of a mass attached to a spring.           (06)

Ans. Consider a mass ‘m’ attached with a spring. If the spring is stretched through a small displacement ‘x’ from its mean position, it exerts a backward for ‘F” on the mass.
According to Hooke’s law, this force is directly proportional to the change of length of “x” of the spring.
Thus, F ∝ x
or   F = K x
Where ‘K’ is a constant known as the spring constant. It is given by  K = F/ x.
The spring constant ‘K’ is defined, as the force required for the unit increase of the length of the spring. Its unit is (Nm-1).
When the spring is released, a restoring force acts on the mass towards the mean position given by
F = – K x   ………… (i)
According to the 2nd law of motion
F = m a   ………… (ii)
From eq (i) and (ii)
m a =  – K x
a = (- K x) / m
or  a  ∝ – x
This relation proves that the acceleration of the mass attached with the spring is directly proportional to its displacement from the mean position. The negative sign shows that acceleration is directed towards the mean position. Therefore the motion of a mass attached with a spring is SHM