# Oswal 61 Sample Question Papers ICSE Class 10 Physics Solutions

## Section-A

(i) (d) Both (a) and (b)

Explanation :

Conditions for total internal reflection

(ii) (a) Increases four times

Explanation :

$$\text{Kinetic energy is =}\space\frac{1}{2}\text{mv}^{2}$$

(iii) (d) All of the above

Explanation :

Different mathematical forms for calculating velocity ratio

(iv) (d) Both (a) and (b)

Explanation :

As option (c) is incorrect both option (a) and (b) are correct for efficiency for machine.

(v) (c) Due to total internal reflection followed by successive refraction of light

Explanation :

Consequence of total internal reflection near the sand surface followed by successive refraction.

(vi) (d) All of these

Explanation :

All alpha, beta, gamma (γ) particles can be stopped by a lead box. Whereas, Alpha (a) and Beta (a) particles can easily be stopped by a paper and an aluminium sheet, respectively. But gamma rays are more penetrating and can be stopped only by lead box.

(vii) (d) 41 F

Explanation :

$$\text{We know,}\frac{\text{C}}{5} =\frac{\text{(F-32)}}{9}$$

Here C = 5.

$$\text{So,\space}\frac{\text{C}}{5} = \frac{\text{(F - 32)}}{9}$$

Solving we get, F = 41° F.

(viii) (b) Parallel

Explanation :

In our household, electrical appliances are connected in a parallel. It is done so as to ensure that all appliances operate at the same voltage. Because the resistance in a parallel arrangement is minimum, thus each appliance receives full voltage. When one appliance fuses, it has no effect on the operation of the other appliances.

(ix) (a) Hydrogen

Explanation :

Among the given substance, hydrogen has the highest specific heat capacity of 14630 J Kg–1 K–1.

Where is for water, Lead and oxygen it is, 4180, 130, and 300 J kg–1 K–1 respectively.

(x) (c) The direction of current flow

Explanation :

Regardless of the direction of current flow, the amount of heat produced in the transmission wire (in general, a current carrying conductor) is determined by the amount of current flowing through it and the resistance of the conductor.

(xi) (c) During absorption of latent heat by a body, the temperature of the body remains constant

Explanation :

During absorption of sensible heat by a body, the temperature of the body changes. During absorption of latent heat by a body, the temperature of the body remains constant. In an isothermal process, temperature is constant everywhere.

(xii) (a) Helium

Explanation :

Emission of alpha (a) particle is alternatively referred as the emission of helium. Both alpha (a) particle and helium has mass number of 4 and atomic number of 2.

(xiii) (b) 836.8 kJ

Explanation :

Given: m = 5 kg; Cp = 4184 J·kg–1·K−1; Δt = (50 – 10) = 40 K.

Thus, required Energy (Q) = m × Cp × Δt = 5 × 4184 × 40 = 836.8 kJ.

(xiv) (c) Specific heat capacity of water is very high.

Explanation :

The reason for using hot water bottles for fomentation is that water does not cool quickly due to high specific heat capacity, so a hot water bottle provides more heat energy for fomentation over a longer period of time.

(xv) (a) Water can extract more heat without raising its temperature significantly.

Explanation :

When water passes through a pipe surrounded by a hot part of the engine, heat energy is removed from those parts. Because water has high specific heat capacity, water in pipes may extract more heat from the environment without significantly raising its temperature. As a result, the car’s radiator and generator are both filled with water.

(i) (a) Refractive index of a medium is the ratio of real depth to apparent depth.

(b) A convex lens can produce a real and inverted image of an object.

(ii) (a) Single fixed pulley.

(b) Drawing water from well.

(iii) A crack in the window pane appears to be silvery due to the phenomenon of total internal reflection. As the ray of light strikes the glass air interface at an angle greater than critical angle, it suffers total internal reflection hence reflects back causing the crack to appear silvery.

(iv) (a) The refractive index for a transparent medium is least for red light.

(b) The refractive index for a transparent medium is most for violet light.

(v) (a) Convex lens is a converging lens while concave lens is a diverging lens.

(b) Convex lens mostly produces a real and inverted image while concave lens always producers a virtual and erect image.

(vi) Water in closed containers such as pressure cookers boil at higher temperatures than normal boiling point as with pressure built inside the cooker raises the boiling point of water.

(vii) (a) If an α particle gains and electron, it would change into a singly ionised helium atom.

(b) If it gains two electrons it would get converted into a helium atom.

(i) (a) Mass number A = number of protons + number of neutrons

Atomic number Z = number of protons.

Number of neutrons = mass number A – atomic number Z = 48 – 18 = 30.

The nucleus X can be written as,

$$^{48}_{18}\text{X}.$$

(b) After the loss of 4 protons, the mass number and the atomic number of the nucleus

$$^{48}_{18}\text{X}\space\text{will decrease by 4.}\\\text{Thus the new nucleus will be}^{44}_{14}\text{Y}.$$

(ii) (a) Time t = 30 sec

Temperature ΔT = 328 – 278 = 50 K

Mass of water (m) = 1 kg

So, energy supplied by the geyser (Q) = power × time = 5000 × 30 = 150000 = 1.5 × 105 J.

(b) No, it is not safe to connect this electric geyser with the live wire. Because even if the switch is off, still the geyser will have access to current. Thus, it is dangerous to the users.

(iii) (a) The equivalent resistance is

$$\bigg(\frac{\text{I}}{\text{R}}\bigg) = \frac{1}{4+4} + \frac{1}{8}.$$

Or, R = 4 ohm.

(b) Current flowing through the battery is = 10/4 = 2.5 A.

(c) If they are connected in series, then the equivalent resistance (R) = 4 + 4 + 8 = 16 ohm.
Current flowing through the battery will be = 10/16 = 0.625 A.

(iv) (a) For maximum work, the angle between the force and displacement should be 0°.

(b) For no work to be done (or zero work), the angle between the force and displacement should be 90°.

$$\text{(v)}\space\text{(a)\space Given : a}^{n}w =\frac{4}{3}\\\therefore\space w^{n}a =\frac{1}{a^{n}w}=\frac{1}{4/3} =\frac{3}{4}$$

(b) The value of the angle of incidence in this case is zero.

## Section-B

(i) By law of conservation of energy

Gravitational potential energy of water = Heat produced

Mass × Acceleration due to gravity × Height = Mass × specific heat capacity × rise in temperature

m.g.h = m.c.θR

Rise in temperature [θR] = [g.h/c]

$$=\frac{10×150}{4200}$$

= 0.36°C

Rise in temperature of water when it strikes at the bottom

= 0.36°C

(ii) Law of conservation of mechanical energy as applied to a simple oscillating pendulum :

(iii) (a) A is a single movable pulley and B is a single fixed pulley.

(b) The purpose of pulley B is to give convenience of direction in application of the effort. [towards gravity]

(c) For this combination of single fixed and single movable pulley,

The mechanical advantage = 2

$$=\frac{\text{Load}}{\text{Effort}} = 2\\\frac{\text{Load}}{2} =\text{Effort}\\\text{Effort required =}\frac{40}{2}$$

= 20 kgf

(i) (a) The man having a box on his head and who climbs up a slope does more work against the force of gravity because he gains potential energy by virtue of his position (height).

(b) The two forces each of 8 N form a couple.

Moment of couple = Either force × Couple arm

= 8 × 1 Nm ( Couple arm = 100 cm = 1 m)

= + 8 Nm (anticlockwise)

(ii)

(iii) (a) The lens used is a concave lens.

(b)

(i) The factors on which intensity of sound depends are :

(a) It is directly proportional to (Amplitude)2

(b) It is directly proportional to surface area of vibrating surface.

(c) It is inversely proportional to the distance of source from listener.

(d) It is directly proportional to density of the medium.

(ii) Law of vibrating strings state that,

When a string is stretched between two fixed points, the frequency of emission is :

(a) directly proportional to the square root of tension in the string.

(b) inversely proportional to length of the string.

(c) inversely proportional to square root of linear density of the string.

(iii) For the first echo,

$$\text{Wave velocity =}2\frac{(\text{distance})}{\text{time}}\\ 340 = 2\frac{X}{3}$$

X = 510 m

For second echo,

$$\text{Wave velocity = 2}\frac{\text{distance}}{\text{time}}\\340 = 2.\frac{7}{6}$$

Y = 1020 m

Total distance between the two cliffs is = 510 + 1020 = 1530 m

(i) (a) According to Lenz’s law, the direction of induced e.m.f is such that it opposes the cause which produces it.

(b) Yes, we can find the direction of induced current using Lenz’s law.

(c) The device shown in the figure is called ‘Toroid.’

(ii) (a) Resistance of the filament (R) = V2/P = (220)2/100 = 484 Ohm.

(b) Safe current (I) = Power rating/Voltage rating = 100/220 = 0.45 A.

(c) As the safe current is 0.45 A, thus using current more than 0.45 A is unsafe to use.

(iii) (a) During a constant-temperature process, latent heat is the energy emitted or absorbed by a body or a thermodynamic system. Changes in phase between liquids, gases, and solids are associated to latent heat.

(b) The term “sensible heat” refers to energy that is transferred as heat and results in a temperature
change in a body.

(c) When the ice in a frozen lake begins to melt, the area around it gets extremely chilly. This is due to the fact that melting the frozen lake requires a significant quantity of heat energy, which is absorbed from the surrounding environment. As a result, the ambient temperature drops and becomes very cold.

(i) (a) North pole.

(b) Electromagnet is a very strong magnet as compared to a permanent magnet.

(ii) (a) Isotopes are atoms of the same element with the same atomic number but different mass numbers.

(b) Carbon has three isotopes, viz.

(iii) (a) A sound’s quality is the characteristic that distinguishes two sounds of equal loudness and pitch, but produced by two distinct instruments.

(b) Difference between music and noise.

1. Music is produced by periodic vibrations, noise is produced by an irregular succession of disturbances.
2. In music the waveform is regular, whereas in noise the waveform is irregular.
3. Music is pleasant to ears, whereas Noise is unpleasant to ears.

(c) When the tuning fork is allowed to vibrate in the air, produces damped vibration.

(i) For hot body (Water at 60°C) :

Let the mass be m1 gram.

T1 = 60°C

T2 = 10°C

ΔT = (60 – 10) = 50°C

c = 4200 J kg–1 °C–1 = 4.2 Jg–1 °C–1

Heat lost by water = mcΔT = m1 × 4.2 × 50 J

For cold body (Ice at 0°C) :

m = 40 g

T1 = 0°C

T2 = 10°C

ΔT = (10 – 0) = 10°C

L = 336 × 103 J kg–1 = 336 J g–1

c = 4.2 Jg–1 °C–1

Heat gained by ice = mL + mcΔT

= 40 × 336 + 40 × 4.2 × 10 = 15120 J

Using principle of calorimetry,

Heat lost by water = Heat gained by ice

or m1 × 4.2 × 50 = 15120

$$\text{or}\space m_{1} =\frac{15120}{4.2×50} = 7.2 g$$

(ii) Heat :

(a) The kinetic energy due to the random motion of molecules of a substance is known as heat energy.

(b) It is measured by using the principle of calorimetry.

(c) It is an additive quantity.

While, temperature :

(a) The quantity which determines the direction of flow of heat between the two bodies kept in contact is called temperature.

(b) It is measured by a thermometer.

(c) It is not an additive quantity.

(iii) (a) B is a good conductor of heat.

(b) B is a better conductor of heat than A because it has a lower specific heat capacity. This means that less heat is required to raise the temperature of 1 g of substance B by 1 K as compared to the heat required for substance A.

(c) Substance A will be preferred for use in car radiators as it absorbs large amount of heat energy without raising its own temperature much because it has a high specific heat capacity.

(d) Substance A will be preferred for fomentation purpose because it has a high specific heat capacity and will release greater amount of heat energy for every 1 K fall in temperature.

#### ICSE 61 Sample Question Papers

All Subjects Combined for Class 10 Exam 2024