Oswal Model Specimen Papers ICSE Class 10 Physics Solutions (Specimen Paper - 7)

Section-A

1. (i) (a) Mirage

Explanation :

Example for total internal reflection

(ii) (d) both (a) and (b)

Explanation :

Moment of force = Force x perpendicular distance

(iii) (b) Class II Lever

Explanation :

Class II lever is present in the human body when we raise the body weight on our toes as the fulcrum is at one end, the load is in the middle and effort by muscles is at the other end.

(iv) (d) All of these

Explanation :

As there is some loss in case of practical machine due to frictional resistance hence all three options are valid.

(v) (d) Scattering of light

Explanation :

The blue colour of the sky is due to the scattering of light. As the wavelength of blue colour is least so it get scattered more. When sunlight passes through the atmosphere, the fine particles in air scatter the blue colour (shorter wavelengths) more strongly than red. The scattered blue light enters our eyes and the sky appears blue to us.

(vi) (a) α

Explanation :

The ionising power of alpha radiation (α) is 100 times that of Beta (β) radiation and 10,000 times that of Gamma (γ) radiation. Thus, α-radiation has maximum ionising power.

(vii) (a) Part AB

Explanation :

From the graph it can be noticed that for part AB, with increase in time there is no change in temperature, thus this part is corresponds to the portion of the latent heat of melting of ice.

(viii) (a) The direct change of solid to vapour.

Explanation :

The phenomena of direct change of solid to vapour is known as sublimation and the phenomena of direct change of liquid to solid is known as solidification.

(ix) (a) Ice

Explanation :

Generally, volume of substance like lead, wax etc. increases on melting, but for ice, it is opposite. For ice, its volume decreases on melting to water.

(x) (a) α < β < γ

Explanation :

Speed of gamma particle is same as speed of light (in vacuum), speed of beta particle is around 90% of the speed of light and speed of alpha particle is around 10⁷ m/s.

(xi) (b) Beta

Explanation :

When beta particle is emitted, the mass number of the daughter particle remain same but the atomic number increases by 1. Hence the given statement indicates the beta particle.

(xii) (b) Faraday law of electromagnetic induction

Explanation :

AC generators work on the principle of Faraday’s law of electromagnetic induction, which states that electromotive force EMF or voltage is generated in a current-carrying conductor that cuts a uniform magnetic field.

(xiii) (b) 2 A

Explanation :

Current rating of fuse =

$$\frac{\text{Total power of the appliances in the circuit}}{\text{Supply voltage}}\\=\frac{440\space\text{W}}{220\space \text{V}}$$

So, the fuse’s current rating should be 2 A.

(xiv) (a) They differ in waveform

Explanation :

Both the figures (a) and (b) have same amplitude ‘a’, also they have same frequency, but they differ in waveform.

(xv) (d) All of the above.

Explanation :

All of the above are examples of radiation’s harmful effects. There are three types of biological effects from nuclear radiation: (1) curable short-term effects including diarrhoea, sore throat, hair loss, nausea, and so on; (2) permanent long-term effects like leukemia and cancer; and (3) hereditary disorders.

2. (i) (a) In a block and tackle system,

Number of pulleys = Velocity ratio of block and tackle system

Therefore, total number of pulleys will be 5.

(b) Yes, the position of daughter nucleus change in a periodic table as compared to the parents nucleus.

$$\text{For\space e.g.,\space }^{14}_{6}\text{C}\xrightarrow{}^{14}_{7}\text{N} + \underset{\text{Beta particle}}{^{0}_{\normalsize-1} e}$$

(c) As beta radiations are negatively charged particle, it will deflect towards positively charged plate while passing through an electric field.

(ii) (a) The energy possessed by a body by virtue of its position or configuration is called potential energy.

(b) Force acting on the body = Mass × Acceleration due to gravity = mg

∴ Work done in taking the body to height h = Force × Displacement = mgh

This work done in lifting the body gets stored in the body in the form of its gravitational potential energy when it is at a height ‘h’.

∴ Potential energy (U) = mgh

(iii) (a) Class I lever.

(b) Pliers.

(iv) (a) The focal length of a lens increases and the power gets decreased.

(b) Refractive index of diamond is 2.42. This means that light travels 2.42 times slower in diamond than in air (or vacuum).

(v) The rough focal length of a convex lens is obtained by forming sharp image of a very distant object on a screen. The distance of the screen from the lens gives us the rough focal length of the lens.

This method is not applicable to a concave lens, as image formed by a concave lens is virtual and it cannot be obtained on a screen.

(vi) (a) Resonance occurs when the frequency of the applied force is equal to the natural frequency of the vibrating body.

(b) (1) Loudness of sound is directly proportional to the square of the amplitude of the vibrating body.

(2) Loudness of sound is directly proportional to the surface area of vibrating body.

(vii) The rear view mirror of a motorbike starts vibrating violently when driven at a particular speed as the frequency of piston of the engine may match the natural frequency of the rear view mirror as a result vibrates violently. This can be avoided by reducing the speed of the motorbike.

3. (i) (a) As we know that virtual, diminished image is formed, the given lens is concave lens.

(b) Given; u = –50 cm, v = –15 cm

$$\frac{1}{f} = \frac{1}{v} -\frac{1}{u}\\=\frac{1}{\normalsize-15}-\frac{1}{-50}=\frac{-10 + 3}{150}\\ f=-\frac{150}{7}=-21.42\space\text{cm}$$

(ii) The two factors affecting lateral displacement are :

(1) Thickness of glass slab

(2) Angle of incidence

(iii) (a) The potential difference between the terminals of a cell is called its electromotive force (or e.m.f.) when no current is drawn from it.

When current is drawn from a cell, the potential difference between the cell’s electrodes is known as the terminal voltage.

(b) To have a high resistance, the filament wire is long and thin. To fit in a small space it is coiled.

(iv) (a) When the frequency of an externally applied periodic force equals the natural frequency of a body, the body begins to vibrate with increased amplitude. This phenomenon is known as resonance.

(b) When the glass rattles, at that moment, its natural frequency corresponds with frequency of piano note, thus resonance takes place, which makes the glass to vibrate violently.

(v) When a fielder stops the ball, the force applied by the fielder is in direction opposite to the direction of motion of the ball (i.e., displacement), so work done by the fielder is negative.

Section-B

4. (i) (a) The resistances B and C are connected in parallel. So their equivalent resistance is,

$$\text{R}_{1}=\frac{4×6}{4 + 6} = 2.4\space Ω.$$

The resistor A is connected in series with R₁, then the equivalent resistance of A, B, and C is

(R₂) = 2.4 + 2 = 4.4 Ω.

The total resistance of the circuit is = R₂ + 0.6 = 4.4 + 0.6 = 5 Ω.

(b) The current drawn from the battery,

$$\text{I =}\frac{\text{e.m.f}}{\text{total resistance}}=\frac{9}{5} = 1.8\space\text{A}$$

Thus, Current flowing through the resistor A is 1.8 A.

(ii) (a) The stone is moving with a variable velocity.

(b) Yes, the stone is moving with uniform acceleration. It is directed towards the centre of circular path.

(iii) (a) At point A :

Height (h) = (x + y) and Velocity = 0

∴ Total energy = Kinetic energy (K) + Potential energy (U)

$$=\frac{1}{2}×m×0^{2} + mg(x+y)\\= mg(x + y)$$

(b) At point B :

Height (h) = y and let velocity = v₁

∴ Total energy = K + U

$$=\frac{1}{2}mv_{1}^{2} + mgy$$

Using the equation of motion,

v² = u² + 2as

⇒ v₁² = 0² + 2gx

or v₁² = 2gx

∴ Total energy =

$$\frac{1}{2}mv_{1}^{2} +mgy\\=\frac{1}{2}m×2gx + mgy\\\lbrack\because\space v_{1}^{2} = 2gx\rbrack$$

= mgx + mgy = mg(x + y)

Height (h) = 0 and let velocity = v

$$\therefore\space \text{Total energy = K + U}\\=\frac{1}{2}mv^{2} + mg×0\\=\frac{1}{2}mv^{2} $$

Using the relation, v² = u² + 2as = 0² + 2g(x + y)

or v² = 2g(x + y)

$$\therefore\space \text{Total energy =}\frac{1}{2}\text{mv}^{2}\\=\frac{1}{2}m×2g(x+y)\\= mg(x+y)$$

(d) The law verified by (a), (b) and (c) above is the law of conservation of energy which states that, energy can neither be created nor be destroyed. It may be transformed from one form to another form, but the total energy of the system remains constant.

5. (i) (a) The completed diagram is shown below :

PQ = Incident ray,

QR = Refracted ray,

RS = Emergent ray, and QR is parallel to BC.

(b) At the position of minimum deviation of the prism,

Angle of incidence = Angle of emergence

or ∠i = ∠e.

(ii) (a) The lens is convex.

(b) The ray diagram is shown alongside :

AB is the object and A′B′ is the image formed.

(iii) (a) A′B′ is the image formed of the object AB placed in front of the lens LL′.

(b) The type of lens used is concave.

6. (i) (a) The phenomenon involved in tuning a radio set to a particular station is resonance.

Resonance is a condition of forced vibrations. When the frequency of an externally applied periodic force on a body readily begins to vibrate with an increased amplitude. This phenomenon is known as resonance.

(b) The frequency of channel is 93.5 MHz

In SI unit, frequency f = 93.5 × 10⁶ Hz

(ii) (a) Clockwise moment = F × r

= 100 gf × 20 cm

= 2000 gf cm

(b) X must be greater than 100 gf i.e., X > 100 gf

(iii) (a) Work done in moving the block from A to B,

= F × s

= 200 N × 3 m = 600 J

(b) Gain in potential energy = mgh = 30 × 10 × 1·5

= 450 J.

7. (i) (a) Lorentz found that a charge moving in a magnetic field, in a direction other than the direction of magnetic field, experiences a force. It is called the Lorentz force.

(b)

Whenever there is a change in magnetic flux linked with a coil, an e.m.f. is induced.
The magnitude of the induced e.m.f. is directly proportional to the rate of change of magnetic flux liked with the coil.

(ii) (a) The heat capacity per unit mass of a substance is described as its specific heat capacity.

i.e, Specific heat capacity =

$$\frac{\text{Heat capacity of the body}}{\text{Mass of the body}}$$

(b) Specific heat capacity of water is 4180 J kg^–1 K^–1.

$$\frac{\text{Applied heat}}{(\text{Mass of the body× Temperature change})}\\=\text{Or\space} 10 =\frac{200}{(m × 20)}$$

Or m = 1 kg.

Thus, the mass of the substance is 1 kg.

(iii) (a) Because alpha radiation (a) has a lower penetration power, it is prevented by the vessel’s walls. As a result, the vessel is secure from alpha radiation. The walls of the vessel cannot stop beta (b) and gamma (g) radiations, hence the vessel is dangerous for both beta and gamma radiations.

(b) Measures for more safety: The sphere’s walls must be made of lead. The radius of the sphere must be large.

(d) On emission of γ- particle, there will be no change in the mass number as well as in atomic number.

8. (i) (a) Given, m = 1 kg = 1000g, L = 336 Jg^–1.

Heat energy required = mL = 1000 g × 336 Jg^–1 = 336000 J = 3.36 × 10⁵ J.

(b) Isotones are atoms with varying numbers of protons but the same number of neutrons. They also differ in the number of electrons they have. For example, $$^{40}_{20}\text{Ar}\space\text{and}\space ^{39}_{19}\text{K}$$

have same number of neutrons but different numbers of protons, thus they are isotones.

(ii) (a) The earth pin is made so thick because the earth pin can never be put into other pin holes of live and neutral connections. Also, because the earth pin must be connected first, it is longer than the
other pins. If the holes are of equal thickness, the appliance may be destroyed if the wrong pin is accidentally placed into the wrong hole.

(b) A short circuit occurs when a live wire makes direct contact with a neutral wire. In this circumstance, resistance in the current’s path drops to virtually. As a result, a large amount of current flows through the live wire.

(iii) (a) As the vibrations are due to external means, thus forced vibrations are those that occur in the table top.

Yes, it will definitely produce a sound.

(b) Resonance will occur when the natural frequency of the table top’s vibrations will be equal to the frequency of the vibrating tuning fork.

(c) Loudness, pitch (shrillness), and quality (timber) are the three key characteristics that are able to distinguish two different sounds.

9. (i) (a) Across PQ the effective resistance is =

$$\frac{(3 + 3)×3}{(3 + 3) + 3}=\frac{18}{9} = 2Ω.$$

(b) Equivalent resistance across terminal XY is = 3 + effective resistance across PQ + 3

= 3 + 2 + 3 = 8 Ω.

The flow of current through the battery I =

$$\frac{\text{Voltage applied}}{\text{Equivalent resistance across terminal XY}}\\=\frac{10}{8} = 1.25\space\text{A}.$$

(ii) (a) South

(b) By passing a stronger current the strength of the magnetic field in increased.

(iii) (a) Because water does not cool rapidly due to its high specific heat capacity, utilising a hot water bottle for fomentation gives more heat energy for fomentation over a longer length of time.

(b) Sublimation is the process in which a solid is directly transformed into vapour, without through the phase of liquid.

Deposition or de-sublimation is the opposite of sublimation, in which a material transitions from a gas to a solid state.