ICSE Class 7 Physics Sample Paper with Solutions Set 01

Question 1
Choose the correct answer out of the four available choices given under each question. [15]

1. A plastic mug full of water appears lighter inside water due to [1 Mark]
(a) Gravitational force
(b) Pressure
(c) Newton's Third Law
(d) Buoyant force

Answer: (d) Buoyant force

When a plastic mug full of water is placed in water, it experiences an upward thrust (buoyant force). As a result, it appears lighter when placed inside water.

Teacher's Note:
a) Buoyant force is the upward force exerted by a fluid on an object placed in it.
b) Students must remember that apparent loss of weight in a fluid is equal to the buoyant force acting on the body.

2. A person gets a severe shock on touching [1 Mark]
(a) a neutral wire
(b) a live wire
(c) an earthing wire
(d) None of above

Answer: (b) a live wire

A person gets a severe electric shock on touching a live wire because it carries current at a high potential.

Teacher's Note:
a) The live wire carries current from the power station to the appliance.
b) Earthing wire is used as a safety measure to prevent electric shocks, whereas neutral wire completes the circuit.

3. A car increases its speed from \( 20\text{ km/h} \) to \( 40\text{ km/h} \) in \( 10\text{ seconds} \). Its acceleration is: [1 Mark]
(a) \( (5/9)\text{ m/s}^{2} \)
(b) \( 2\text{ m/s}^{2} \)
(c) \( (-5/9)\text{ m/s}^{2} \)
(d) \( -2\text{ m/s}^{2} \)

Answer: (a) \( (5/9)\text{ m/s}^{2} \)

Initial velocity \( u = 20\text{ km/h} = 20 \times \frac{5}{18}\text{ m/s} = \frac{50}{9}\text{ m/s} \). Final velocity \( v = 40\text{ km/h} = 40 \times \frac{5}{18}\text{ m/s} = \frac{100}{9}\text{ m/s} \). Time \( t = 10\text{ s} \). Acceleration \( a = \frac{v - u}{t} = \frac{\frac{100}{9} - \frac{50}{9}}{10} = \frac{50}{9 \times 10} = \frac{5}{9}\text{ m/s}^{2} \).

Teacher's Note:
a) Always convert speeds from \( \text{km/h} \) to \( \text{m/s} \) by multiplying with \( \frac{5}{18} \) before calculating acceleration.
b) Pay close attention to the units requested in the options.

4. Which of the following is not a characteristic of a plane mirror? [1 Mark]
(a) The magnification of the image formed is 1.
(b) The image can be formed on a screen
(c) The image formed is erect.
(d) The image is formed at the same distance behind the mirror as the object is in front of it.

Answer: (b) The image can be formed on a screen

Plane mirrors always form virtual images, and virtual images cannot be projected or formed on a screen.

Teacher's Note:
a) Real images can be caught on a screen, whereas virtual images appear only in the mirror.
b) Plane mirrors form erect images of the same size as the object with a magnification of 1.

5. The ratio of C.G.S. to M.K.S. unit of acceleration is: [1 Mark]
(a) \( 1 : 1 \)
(b) \( 1 : 10 \)
(c) \( 1 : 100 \)
(d) \( 10 : 1 \)

Answer: (c) \( 1 : 100 \)

C.G.S. unit of acceleration is \( 1\text{ cm/s}^{2} \) and M.K.S. unit is \( 1\text{ m/s}^{2} \). Since \( 1\text{ m} = 100\text{ cm} \), the ratio is \( \frac{1\text{ cm/s}^{2}}{100\text{ cm/s}^{2}} = 1 : 100 \).

Teacher's Note:
a) Always convert both units to the same system (either CGS or MKS) before taking the ratio.
b) Common mistake is to invert the ratio as \( 100 : 1 \).

6. Pick the odd one out in terms of behavior towards light. [1 Mark]
(a) Air
(b) Water
(c) Glass
(d) Milk

Answer: (d) Milk

Milk is an opaque object, whereas air, water, and glass are transparent media.

Teacher's Note:
a) Transparent substances allow light to pass through them completely, while opaque substances do not.
b) Milk scatters light and does not let it pass clearly, making it opaque.

7. The size of the image formed by a plane mirror is [1 Mark]
(a) Smaller than the object
(b) Same as that of the object
(c) Larger than the object
(d) None of the above

Answer: (b) Same as that of the object

An image formed by a plane mirror is always of the same size as the object.

Teacher's Note:
a) The magnification for a plane mirror is always equal to \( +1 \).
b) The object distance is also equal to the image distance in a plane mirror.

8. Let the internal circuit of a torch contain a cell, key and a bulb connected with wires. What happens when the torch is switched on? [1 Mark]
(a) Key closes, current does not flow and the bulb glows
(b) Key closes, current flows and bulb glows
(c) Key opens, current flows and the bulb glows
(d) Key opens, current does not flow and the bulb does not glow

Answer: (b) Key closes, current flows and bulb glows

When a torch is switched on, the switch/key is closed to complete the circuit, allowing electric current to flow so the bulb glows.

Teacher's Note:
a) A closed key completes the electrical path.
b) An open key breaks the circuit and stops the flow of current.

9. The instrument used to produce sound of a fixed frequency: [1 Mark]
(a) simple pendulum
(b) thermometer
(c) tuning fork
(d) metre

Answer: (c) tuning fork

A tuning fork is an acoustic resonator that produces a pure musical tone of a single, fixed frequency when struck.

Teacher's Note:
a) Tuning forks are widely used in laboratories to demonstrate sound waves and frequency.
b) Thermometer measures temperature and pendulum measures time intervals.

10. Sea breeze blows during the [1 Mark]
(a) Day
(b) Night
(c) Summer
(d) Evening

Answer: (a) Day

Sea breeze blows during the day because land heats up faster than water, causing warm air over land to rise and cooler air from the sea to rush in.

Teacher's Note:
a) Convection currents drive both sea breezes and land breezes.
b) Land breezes blow during the night when land cools down faster than the sea.

11. In a concave mirror, the image is inverted and the same size as the object when the object is placed at the [1 Mark]
(a) Principal Focus
(b) Centre of curvature
(c) Between the focus and the centre of curvature
(d) Between the focus and the pole of mirror

Answer: (b) centre of curvature

The image formed by a concave mirror is real, inverted, and of the same size as the object only when the object is placed at the centre of curvature.

Teacher's Note:
a) When an object is at \( C \), its image is also formed at \( C \).
b) Students must practice ray diagrams for all standard object positions in front of a concave mirror.

12. Which of the following voices is likely to have minimum frequency? [1 Mark]
(a) Baby girl
(b) Baby boy
(c) A man
(d) A woman

Answer: (c) A man

Frequency of sound is directly proportional to its pitch. An adult man has a thicker vocal cord producing a lower pitch, hence the minimum frequency compared to women and babies.

Teacher's Note:
a) Women and children have higher pitched voices due to higher frequency vibrations.
b) Pitch is a characteristic of sound determined by its frequency.

13. If we want to determine the volume of a solid by immersing it in water, the solid should be [1 Mark]
(a) lighter than water
(b) heavier than water
(c) insoluble in water
(d) heavier than water and insoluble in it

Answer: (d) heavier than water and insoluble in it

To find the volume by complete immersion, the solid must sink (heavier than water) and not dissolve or react with water (insoluble in it).

Teacher's Note:
a) If the solid floats, it will not displace its total volume.
b) If it dissolves, the volume measurement using a graduated cylinder will be inaccurate.

14. In hot countries, it is preferred to wear light colours on a hot day because [1 Mark]
(a) light colours are poor absorbers of heat
(b) light colours are good radiators of heat
(c) light colours are good absorbers of heat
(d) light colours are poor radiators of heat

Answer: (a) light colours are poor absorbers of heat

Light-colored clothes reflect most of the heat radiation falling on them and are poor absorbers of heat, keeping the body cool.

Teacher's Note:
a) Dark colors are good absorbers and poor reflectors of heat.
b) This principle is applied in painting buildings white in hot regions.

15. Light causes the [1 Mark]
(a) sensation of heat
(b) sensation of sound
(c) sensation of sight
(d) sensation of touch

Answer: (c) sensation of sight

Light is a form of energy that enables us to see objects by producing the sensation of sight in our eyes.

Teacher's Note:
a) Sound produces the sensation of hearing.
b) Heat produces the sensation of warmth or temperature change.

Question 2

(A) Answer the following questions in one word or one sentence. [5]
1. Name the unit used to measure the loudness of sound. [1 Mark]

Answer:
The loudness of sound is measured in decibels (\( \text{dB} \)).

Teacher's Note:
a) The decibel scale is logarithmic and quantifies sound levels.
b) Sounds above \( 80\text{ dB} \) can be harmful to human ears.

2. What is the law of length? [1 Mark]

Answer:
The time period of a simple pendulum is directly proportional to the square root of its effective length.

Teacher's Note:
a) Formula: \( T \propto \sqrt{l} \).
b) Ensure students mention that time period increases as the length of the pendulum increases.

3. Which lens would you prefer to use while reading small letters found in a dictionary? [1 Mark]

Answer:
A convex lens.

Teacher's Note:
a) A convex lens acts as a magnifying glass when the object is placed within its focal length.
b) It produces a magnified and erect virtual image.

4. Name the temperature scale which does not have negative temperature readings. [1 Mark]

Answer:
Kelvin scale.

Teacher's Note:
a) Absolute zero (\( 0\text{ K} \) or \( -273.15^{\circ}\text{C} \)) is the lowest possible temperature on the Kelvin scale.
b) There are no negative numbers on the Kelvin absolute temperature scale.

5. What happens when two bodies are rubbed together? [1 Mark]

Answer:
They get electrically charged due to the transfer of electrons from one body to the other.

Teacher's Note:
a) This method of charging is called electrification by friction.
b) The body that loses electrons acquires a positive charge, while the one that gains electrons acquires a negative charge.

(B) Fill in the blanks and rewrite the sentences: [5]
1. No medium is required for the transfer of heat by the process of ________. [1 Mark]

Answer:
radiation.

Teacher's Note:
a) Radiation can travel through a vacuum, unlike conduction and convection.
b) Heat from the sun reaches the earth through radiation.

2. A ________ mirror can form a real and inverted image. [1 Mark]

Answer:
concave.

Teacher's Note:
a) Convex mirrors always form virtual and erect images.
b) Concave mirrors can form both real and virtual images depending on object position.

3. ___________ is the characteristic property of a substance, which decreases with an increase in temperature. [1 Mark]

Answer:
Density.

Teacher's Note:
a) As temperature increases, substances generally expand, increasing volume and thus decreasing density.
b) Water shows anomalous expansion between \( 0^{\circ}\text{C} \) and \( 4^{\circ}\text{C} \).

4. A collection of rays is known as _____________ of light. [1 Mark]

Answer:
beam.

Teacher's Note:
a) A single line representing the path of light is a ray.
b) A bundle or collection of rays forms a beam of light (parallel, divergent, or convergent).

5. When a body travels with uniform velocity, its acceleration is_________. [1 Mark]

Answer:
zero.

Teacher's Note:
a) Acceleration is the rate of change of velocity with time.
b) If velocity is constant, the change in velocity is zero.

Question 3

(A) Match the items in column A with the appropriate items in column B. [5]

Answer:
Pitch matches with Frequency.
When two oppositely charged clouds approach each other matches with Lightning produced.
Used by dentist to see enlarged image of teeth matches with A concave mirror.
Absolute zero matches with \( -273^{\circ}\text{K} \).
Acceleration matches with \( \text{m/s}^{2} \).

Teacher's Note:
a) Students should carefully match each physical quantity or phenomenon with its correct definition or unit.
b) Absolute zero is properly denoted as \( 0\text{ K} \), though \( -273^{\circ}\text{C} \) or \( -273^{\circ}\text{K} \) represents the traditional textbook reference in this curriculum level.

(B) Define the following: [5]
1. Rotational motion [1 Mark]

Answer:
When an object turns about a fixed axis, it is called rotational motion.

Teacher's Note:
a) Every particle of the body moves in a circle whose center lies on the axis of rotation.
b) Example: Motion of a spinning top or a rotating fan blade.

2. Angle of incidence [1 Mark]

Answer:
The angle formed between the incident ray and the normal at the point of incidence is called the angle of incidence.

Teacher's Note:
a) It is usually denoted by the symbol \( i \).
b) According to the laws of reflection, the angle of incidence is always equal to the angle of reflection.

3. Infrasonic vibrations. [1 Mark]

Answer:
The vibrations whose frequencies are less than \( 20\text{ Hz} \) are called infrasonic vibrations.

Teacher's Note:
a) Human ears cannot detect infrasonic sounds.
b) Animals like whales and elephants communicate using infrasonic waves.

4. Electroplating [1 Mark]

Answer:
When an electric current is passed through an electrolyte, the positive metal ions move to the cathode and get uniformly coated on the object kept as the cathode. This process is called electroplating.

Teacher's Note:
a) It is an application of the chemical effect of electric current.
b) Used widely for coating objects with corrosion-resistant or shiny metals like gold, silver, or chromium.

5. Radiation [1 Mark]

Answer:
It is the transfer of heat energy from a hot body to a cold body by means of heat rays without requiring any medium between the two bodies.

Teacher's Note:
a) Radiation travels at the speed of light in straight lines.
b) It does not heat the intervening medium.

Question 4

(A) Identify and classify the following types of motions as rotatory, vibratory, periodic, or translatory motion: [5]

Answer:
As shown in the classification table above.

Teacher's Note:
a) Objects can sometimes exhibit multiple types of motion simultaneously, such as a rolling wheel having both translation and rotation.
b) Periodic motion repeats itself in equal intervals of time.

(B) Give one word for the following [5]
1. When an object is placed over a liquid whose density is less than the density of the object, the object will [1 Mark]

Answer:
Sink.

Teacher's Note:
a) An object sinks if its density is greater than that of the liquid.
b) An object floats if its density is less than or equal to the liquid.

2. The Sun is completely blocked by the Moon. [1 Mark]

Answer:
Total solar eclipse.

Teacher's Note:
a) Occurs when the moon comes directly between the sun and the earth.
b) Blocks sunlight completely for observers in the umbra region.

3. The method which determine the distance of sound of reflecting surface by producing echo. [1 Mark]

Answer:
SONAR.

Teacher's Note:
a) Stands for Sound Navigation and Ranging.
b) Uses ultrasonic waves to measure underwater distances.

4. The property which is used to generate electricity in generator. [1 Mark]

Answer:
Electromagnetic induction.

Teacher's Note:
a) Discovered by Michael Faraday.
b) Involves producing an electric current by moving a conductor through a magnetic field.

5. The maximum displacement of the bob on either side of the mean position is [1 Mark]

Answer:
Amplitude.

Teacher's Note:
a) Amplitude is a key characteristic of wave motion and oscillations.
b) Measured in meters (\( \text{m} \)).

Question 5

(A) State whether the following statements are True or False [5]
1. Inertia is the specific property of a body by virtue of which the body changes its state of rest by itself. [1 Mark]

Answer:
False. (Inertia is the property by virtue of which a body resists any change in its state of rest or uniform motion.)

Teacher's Note:
a) Bodies cannot change their state by themselves without an external force.
b) This is Newton's First Law of Motion.

2. Designers of wallpapers and fabrics and artists use periscopes to get ideas for new patterns. [1 Mark]

Answer:
False. (Designers and artists use kaleidoscopes to get ideas for new patterns.)

Teacher's Note:
a) Kaleidoscopes use multiple reflections from inclined mirrors to create symmetrical patterns.
b) Periscopes are used to view objects from a hidden position.

3. Formation of images is done by ray diagram. [1 Mark]

Answer:
True.

Teacher's Note:
a) Ray diagrams help locate image position, size, and nature.
b) Straight lines with arrowheads represent rays of light.

4. When the chemicals in an electric cell are used up, the electric cell stops producing electricity. [1 Mark]

Answer:
True.

Teacher's Note:
a) Cells convert chemical energy into electrical energy.
b) Once chemicals are exhausted, the cell is 'dead' and must be replaced or recharged.

5. The air from the sea is called the warm air. [1 Mark]

Answer:
False. (The air from the sea is cool air, known as sea breeze.)

Teacher's Note:
a) Warm air rises over the land during daytime.
b) Cooler air rushes in from the sea to take its place.

(B)
1. Give reasons. Cooking pots are provided with wooden or plastic handles. [2 Marks]

Answer:
1. Wood and plastic are bad conductors (insulators) of heat.
2. Hence, heat from the hot cooking appliance does not flow to our hands, allowing us to handle hot pots safely without burns.

Teacher's Note:
a) Metals are good conductors of heat, making pot bodies heat up quickly.
b) Insulating handles prevent thermal energy transfer to the user's hands.

2. What is a pinhole camera? How does the letter F appear in a pin hole camera? [3 Marks]

Answer:
1. A pinhole camera is a simple optical device without a lens, consisting of a light-proof box with a single small aperture through which light enters to form an inverted image on a screen.
2. The image of the letter F through a pinhole camera appears inverted (upside down and laterally inverted / flipped horizontally and vertically).
[Figure: Diagram showing object F in front of a pinhole, with light rays passing through the pinhole aperture to form an inverted and laterally reversed image on the inner screen sensor]

Teacher's Note:
a) Pinhole cameras work on the principle of rectilinear propagation of light.
b) The image formed is always real and inverted.

Question 6
Answer the following questions in short:

1. Pick out the conductors and insulators from the list: Brass, mica, air, silver, aluminium, human body, lead, copper, glass, plastic, bakelite, rubber, common salt solution, alcohol, mercury, wool, leather, ebonite [2 Marks]

Answer:
Conductors: Brass, aluminium, mercury, silver, copper, human body, common salt solution, alcohol.
Insulators: Air, mica, lead, glass, plastic, bakelite, rubber, wool, leather, ebonite.

Teacher's Note:
a) Conductors allow electric current to pass through them easily.
b) Insulators offer high resistance and block current flow.

2. On what factors does the time period of a simple pendulum depend? [2 Marks]

Answer:
1. The effective length of the pendulum (\( l \)).
2. Acceleration due to gravity at that place (\( g \)).

Teacher's Note:
a) Formula: \( T = 2\pi\sqrt{\frac{l}{g}} \).
b) It is independent of the mass of the bob and small amplitudes of oscillation.

3. What is the radius of curvature of a spherical mirror whose focal length is -0.5 cm? Also name the type of mirror? [2 Marks]

Answer:
Radius of curvature (\( R \)) = \( 2 \times \text{Focal length } (f) \).
\( R = 2 \times (-0.5\text{ cm}) = -1\text{ cm} \).
Type of mirror: Concave mirror, since its focal length is negative.

Teacher's Note:
a) The radius of curvature is always twice the focal length in spherical mirrors.
b) Concave mirrors have negative focal lengths according to sign conventions.

4. Find the odd man out and give reasons for your choice. i. Loudness, reflection, pitch, quality. ii. 40 decibels, 70 decibels, 150 decibels, 90decibels. [2 Marks]

Answer:
i. Reflection - as it is not a characteristic of sound, while loudness, pitch, and quality are characteristics of sound.
ii. 150 decibels - as it is an undesirable, very loud, and painful sound, thus considered to be noise, whereas the others are moderate sound levels.

Teacher's Note:
a) Sound characteristics include pitch, loudness, and quality (timbre).
b) Sound levels above \( 120\text{ dB} \) cause pain and discomfort.

5. Express 78 tonnes in kilograms. [2 Marks]

Answer:
\( 1\text{ tonne} = 10\text{ quintals} \)
\( 78\text{ tonnes} = 78 \times 10 = 780\text{ quintals} \)
\( 1\text{ quintal} = 100\text{ kg} \)
\( 780\text{ quintals} = 780 \times 100 = 78,000\text{ kg} \)

Teacher's Note:
a) Always show intermediate unit conversion steps clearly.
b) \( 1\text{ tonne} = 1,000\text{ kg} \), directly giving \( 78 \times 1,000 = 78,000\text{ kg} \).

Question 7

(A)
1. Draw ray diagrams to show the image formation by a concave mirror, when it is placed (i) beyond C (ii) at C [4 Marks]

Answer:
1. (i) Beyond C: When the object is placed beyond the centre of curvature \( C \), a real, inverted, and diminished image is formed between \( C \) and \( F \).
[Figure: Ray diagram showing object AB placed beyond centre of curvature C in front of concave mirror MN. Incident rays from A parallel to principal axis passing through focus F, and passing through F reflecting parallel, intersect between C and F to form inverted diminished image A'B']
2. (ii) At C: When the object is placed at the centre of curvature \( C \), a real, inverted, and same-sized image is formed at \( C \).
[Figure: Ray diagram showing object AB placed at centre of curvature C in front of concave mirror MN. Incident rays reflect to form real, inverted image A'B' of identical size exactly at C]

Teacher's Note:
a) Arrowheads on light rays are mandatory in ray diagrams to indicate the direction of propagation.
b) Ensure principal focus \( F \) and centre of curvature \( C \) are spaced correctly.

2. Explain the effects of heat. [3 Marks]

Answer:
1. Change in temperature of the body: Heating a body increases its temperature, while cooling decreases it.
2. Change in state of matter: Heat energy causes a substance to change its physical state from solid to liquid, or liquid to gas (melting, boiling).
3. Change in shape and size: Heat causes thermal expansion in bodies, altering their dimensions and shape.

Teacher's Note:
a) Heat can also kill harmful microorganisms in substances like water and milk when boiled.
b) State change occurs at constant temperature during phase transitions.

(B)
1. What is an echo? [1 Mark]

Answer:
The repetition of sound caused by the reflection of sound waves from a high building, hill, or any large reflecting surface is called an echo.

Teacher's Note:
a) Persistence of human hearing is about \( \frac{1}{10}\text{th} \) of a second (\( 0.1\text{ s} \)).
b) Reflected sound must reach the ear after \( 0.1\text{ s} \) to be heard distinctly as an echo.

2. State two conditions necessary for hearing an echo. [2 Marks]

Answer:
1. The minimum distance between the source of sound and the reflecting surface should be at least \( 17\text{ metres} \).
2. The reflecting obstacle must be large enough (such as a high-rise building, hill, or cliff) compared to the wavelength of sound.

Teacher's Note:
a) Sound travels approximately \( 340\text{ m/s} \); in \( 0.1\text{ s} \) it covers \( 34\text{ m} \) (round trip), meaning a minimum one-way distance of \( 17\text{ m} \) is required.
b) Soft furnishings absorb sound and prevent echoes.