class 7 Science

Short Questions and Answers

Q1: What causes day and night on Earth?
Ans: Day and night occur due to the rotation of the Earth on its axis. As the Earth rotates, one side faces the Sun (day), while the opposite side is in darkness (night).

Q2: In which direction does the Earth rotate?
Ans: The Earth rotates in an anti-clockwise direction from the North Pole, which means it rotates from West to East.

Q3: Why does the Sun appear to rise in the East and set in the West?
Ans: The Sun appears to rise in the East and set in the West because the Earth rotates from West to East. As the Earth rotates, different parts of it move into and out of sunlight.

Q4: How long does the Earth take to complete one full rotation?
Ans: The Earth completes one full rotation in approximately 24 hours.

Q5: What is a solar eclipse?
Ans: A solar eclipse occurs when the Moon comes between the Earth and the Sun, blocking the Sun’s light from reaching the Earth.

Q6: How long does the Earth take to complete one revolution around the Sun?
Ans: The Earth completes one revolution around the Sun in about 365 days and 6 hours.

Q7: Why do different stars appear in the night sky over the course of a year?
Ans: The position of stars in the night sky changes due to the Earth’s revolution around the Sun. As Earth moves along its orbit, the stars visible at night also shift.

Q8: What is the effect of the Earth’s axial tilt on seasons?
Ans: The Earth’s axial tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year, leading to the changing seasons.

Q9: What is a lunar eclipse?
Ans: A lunar eclipse occurs when the Earth comes between the Sun and the Moon, blocking sunlight from reaching the Moon. This casts a shadow on the Moon.

Q10: How can we safely observe a solar eclipse?
Ans: A solar eclipse should not be viewed directly with the naked eye. Special protective glasses or indirect methods (like using a mirror to project the image) should be used for safe viewing.Long Questions and Answers

Q1: Explain the process of Earth’s rotation and how it affects the day-night cycle.
Ans: The Earth rotates on its axis, which is an imaginary line running from the North Pole to the South Pole. This rotation occurs in an anti-clockwise direction when viewed from above the North Pole. As the Earth rotates, different parts of the planet move into sunlight, experiencing daytime, while the opposite side is in darkness, experiencing night. This rotation is the primary cause of the cycle of day and night, with each full rotation taking approximately 24 hours.

Q2: Describe the difference between Earth’s rotation and revolution.
Ans: Earth’s rotation refers to its spinning on its axis, taking about 24 hours to complete one rotation. This causes day and night. On the other hand, Earth’s revolution is the motion of the Earth around the Sun, taking approximately 365 days and 6 hours to complete one full orbit. The revolution is responsible for the changing seasons on Earth.

Q3: How do the Earth’s rotation and revolution contribute to the changing seasons?
Ans: The Earth’s rotation gives rise to the day-night cycle, but it is the revolution that causes the changing seasons. Due to the Earth’s axial tilt, different hemispheres receive varying amounts of sunlight throughout the year. When the Northern Hemisphere is tilted towards the Sun, it experiences summer, while the Southern Hemisphere experiences winter. In December, the tilt reverses, and the Northern Hemisphere experiences winter, while the Southern Hemisphere experiences summer. This axial tilt and Earth’s orbit around the Sun are the main factors contributing to the seasonal changes.

Q4: What is the geometry behind a solar eclipse? Explain how it occurs.
Ans: A solar eclipse occurs when the Moon comes between the Sun and the Earth, blocking the Sun’s light from reaching the Earth. The Moon casts a shadow on Earth, which can either be a total or partial eclipse, depending on the alignment of the Sun, Moon, and Earth. In a total solar eclipse, the Moon completely covers the Sun, and the sky becomes dark during the day. A partial solar eclipse occurs when only a part of the Sun is blocked. This event is brief, as the Moon’s shadow moves across the Earth’s surface due to the Earth’s rotation.

Q5: Discuss the safety precautions that should be followed while observing a solar eclipse.
Ans: It is crucial not to look directly at a solar eclipse with the naked eye, as it can cause serious eye damage. Special eclipse glasses that meet safety standards should be used for direct viewing. Alternatively, indirect methods, such as using a mirror to project the Sun’s image onto a screen, can also be used. Never observe a solar eclipse through regular sunglasses, binoculars, or telescopes unless they are equipped with proper solar filters. It is also recommended to participate in organized eclipse viewing events where experts provide the necessary equipment and safety instructions.

Short Question Answer:

Q1: What is the difference between luminous and non-luminous objects?

Answer: Luminous objects are those that emit their own light, such as the Sun, stars, and fireflies. Non-luminous objects do not emit light; they reflect light from luminous objects. The Moon is an example of a non-luminous object because it only reflects sunlight.

Q2: How does light travel?

Answer: Light travels in a straight line, as demonstrated by various activities where light passes through holes or is blocked by objects. This straight-line travel is known as the rectilinear propagation of light.

Q3: What happens when light passes through transparent materials?

Answer: When light passes through transparent materials, like glass or clear water, it passes almost completely through them, allowing us to see through the material clearly. Transparent materials allow most of the light to pass through without scattering.

Q4: How does the Moon produce light?

Answer: The Moon does not produce its own light. It is a non-luminous object that reflects the light of the Sun. This reflected light is what we see as moonlight. The surface of the Moon reflects sunlight, but because the surface is rough, the light is scattered.

Q5: What is lateral inversion in mirrors?

Answer: Lateral inversion refers to the reversal of left and right in an image formed by a plane mirror. When you look into a mirror, the image appears reversed, such as your left hand appearing as the right hand in the reflection.

Q6: Why do opaque objects create shadows?

Answer: Opaque objects block the path of light, and as a result, a dark area forms on the opposite side of the object. This dark area is the shadow. Since opaque objects completely block light, they create the darkest shadows.

Q7: What happens when light is reflected by a mirror?

Answer: When light strikes a mirror, it changes direction and is reflected. The angle at which light hits the mirror (angle of incidence) is equal to the angle at which it is reflected (angle of reflection). This is known as the law of reflection.

Q8: How do you form a shadow using a torch?

Answer: To form a shadow, you need a light source (like a torch), an opaque object to block the light, and a screen (like a wall or a cardboard). When the object blocks the light, the shadow forms on the screen in the shape of the object.

Q9: How does a periscope work?

Answer: A periscope allows you to see objects that are out of your direct line of sight by using two mirrors placed at 45° angles inside a box. Light entering the periscope is reflected off both mirrors, allowing you to see over obstacles or around corners.

Q10: What is the role of mirrors in forming images?

Answer: Mirrors form images by reflecting light. The image formed in a plane mirror is virtual, meaning it cannot be captured on a screen. The image is always upright, of the same size as the object, and laterally inverted (left-right reversal).

Long Question Answer

Q1: Explain how light travels and what happens when it hits different objects.

Answer: Light travels in a straight line. This is known as the rectilinear propagation of light. When light strikes different materials, it behaves in different ways:

• Transparent materials, like glass and clear water, allow light to pass through them completely. This means we can see through them clearly.
• Translucent materials, like tracing paper or frosted glass, let some light pass through but not all. They cause the light to scatter, so objects on the other side are not clearly visible.
• Opaque materials, like cardboard or wood, block light completely. No light passes through opaque objects, which is why we can’t see through them.

In experiments, when you place objects in the path of a torch beam, you can observe that light passes through transparent materials but either partially or completely blocks through translucent and opaque materials.

Q2: Describe the process of shadow formation.

Answer: Shadows are formed when an object blocks the path of light. Since light travels in a straight line, when it hits an opaque object, the area behind the object will not receive light. This creates a shadow. The size, shape, and sharpness of the shadow depend on the position of the object, the light source, and the screen where the shadow is cast.

• Opaque objects create darker shadows because they block most or all of the light.
• Translucent objects create lighter shadows because some light passes through them.
• Even transparent objects, like clear plastic, can create faint shadows, as they only slightly allow light to pass through.

When you move the object closer to the light source, the shadow becomes larger. If you move the object further away, the shadow becomes smaller. The position of the object also affects the sharpness of the shadow—closer objects create sharp shadows, while distant objects create blurry ones.

Q3: How do mirrors reflect light?

Answer: Mirrors reflect light by changing the direction of the light that falls on them. When light hits a mirror, it bounces off the surface. This reflection allows us to see an image of objects placed in front of the mirror. The reflection follows a law called the law of reflection, which states that the angle at which the light hits the mirror (angle of incidence) is equal to the angle at which it reflects off (angle of reflection).

In experiments with mirrors:

• If you direct light onto a flat, shiny surface (like a mirror), it will reflect in a straight line to another surface or wall.
• If the mirror is tilted, the direction of the reflected light will change, but the angle of incidence will always equal the angle of reflection.

The images formed in a plane mirror are:

• Erect (not upside down),
• Same size as the object,
• Laterally inverted (left and right are reversed),
• Cannot be projected on a screen because they are virtual.

Q4: Explain how the Moon reflects light.

Answer: The Moon does not produce its own light. It is a non-luminous object, which means it doesn’t emit light. Instead, the Moon reflects the light of the Sun that falls on its surface. This reflected light is what we see as moonlight.

The Moon’s surface is rough and uneven, so the light it reflects is scattered. This is why moonlight is not as bright as sunlight. During the day, we can’t see the moon’s light because the sunlight is much brighter. But at night, when the Sun’s light is not in the sky, the moon’s reflection becomes visible to us.

This phenomenon of reflection is similar to how mirrors work. The only difference is that the Moon’s surface reflects light unevenly due to its craters and rough texture, which is why the moonlight we see is softer and more diffused than sunlight.

Q5: How can we create a periscope and how does it work?

Answer: A periscope is a simple device that allows you to see things that are hidden from direct view. It works by using two mirrors arranged at an angle to each other. Here’s how to make a simple periscope:

• Take a rectangular box and cut two holes on opposite sides.
• Place two plane mirrors inside the box at an angle of 45° to each other.
• Through one hole, you can look into the periscope, and through the other hole, you can see the image reflected by the mirrors.

When light enters through the first hole, it strikes the first mirror and is reflected onto the second mirror. The second mirror then reflects the light to the second hole, allowing you to see objects that are outside the direct line of sight.

Periscopes are often used in submarines, tanks, or by soldiers to observe the surroundings without exposing themselves. They are useful for seeing over obstacles or around corners.

Q1: How do plants grow?
Answer: Plants grow by obtaining water, sunlight, and nutrients from the soil. Visible growth includes new leaves, branches, increased height, and thicker stems.

Q2: What is photosynthesis?
Answer: Photosynthesis is the process by which plants use sunlight, chlorophyll, carbon dioxide, and water to produce glucose and oxygen. It mainly occurs in the leaves.

Q3: Why are leaves called the “food factories” of plants?
Answer: Leaves are called the “food factories” because they perform photosynthesis, producing food (glucose) for the plant using sunlight, water, and carbon dioxide.

Q4: What is the role of chlorophyll in plants?
Answer: Chlorophyll is a green pigment in leaves that captures sunlight, which is necessary for photosynthesis. It helps convert light energy into chemical energy to produce food.

Q5: What is the function of stomata in leaves?
Answer: Stomata are tiny pores on the surface of leaves that allow the exchange of gases. They take in carbon dioxide for photosynthesis and release oxygen as a by-product.

Q6: How do plants absorb water and minerals?
Answer: Plants absorb water and minerals through their roots. These are then transported to other parts of the plant by xylem, a specialized vascular tissue.

Q7: What is the difference between xylem and phloem?
Answer: Xylem transports water and minerals from the roots to the rest of the plant, while phloem transports food (glucose or starch) produced in the leaves to other parts of the plant.

Q8: Do plants respire?
Answer: Yes, plants respire to produce energy for growth and other functions. Respiration involves breaking down glucose with oxygen, releasing carbon dioxide, water, and energy.

Q9: What is the importance of carbon dioxide in photosynthesis?
Answer: Carbon dioxide is essential for photosynthesis. Without it, plants cannot produce starch, even if they have sunlight, water, and chlorophyll.

Q10: What happens to the starch produced by plants during photosynthesis?
Answer: The starch produced in plants is stored for later use. It serves as a carbohydrate reserve that can be converted into glucose when needed for energy.

Long Answer Questions

Q1: Explain the process of photosynthesis in detail.
Answer: Photosynthesis is a process by which plants produce their own food. It takes place in the leaves, mainly in the chloroplasts, which contain chlorophyll. During photosynthesis, plants absorb sunlight through chlorophyll. The sunlight, along with water absorbed by the roots and carbon dioxide from the air (through stomata), reacts to produce glucose (a simple carbohydrate) and oxygen. The word equation for photosynthesis is:
Carbon dioxide + Water → Glucose + Oxygen
Glucose is used by the plant as an immediate energy source or stored as starch for later use. Oxygen is released as a by-product, which is crucial for the survival of other organisms, including humans.

Q2: How do plants transport water, minerals, and food within their structure?
Answer: Plants have a specialized transport system to move water, minerals, and food to different parts. Water and minerals are absorbed by the roots from the soil and transported upwards to the leaves through xylem tissue. The xylem acts like a pipeline, carrying water and minerals to the stems, leaves, and flowers.
Food produced during photosynthesis (mainly glucose) is transported through phloem, another type of vascular tissue. The phloem carries the food from the leaves, where it is made, to other parts of the plant like roots, stems, and fruits. These processes ensure that the plant gets the necessary nutrients for growth, energy, and reproduction.

Q3: Describe the role of sunlight, water, and chlorophyll in plant growth and food production.
Answer: Sunlight, water, and chlorophyll are essential for plant growth and food production.

• Sunlight provides energy for photosynthesis. Chlorophyll absorbs sunlight and helps convert it into chemical energy.
• Water is necessary for transporting nutrients through the plant and helps maintain its structure. It also participates in photosynthesis by combining with carbon dioxide to form glucose.
• Chlorophyll, the green pigment in leaves, captures sunlight and enables plants to perform photosynthesis. Without chlorophyll, plants cannot produce food effectively, even if they have sunlight and water.

Q4: What is respiration in plants, and how does it differ from photosynthesis?
Answer: Respiration in plants is a process where plants break down glucose (produced during photosynthesis) using oxygen to release energy. The equation for respiration is:
Glucose + Oxygen → Carbon dioxide + Water + Energy
This energy is used for growth, repair, and other functions within the plant. Respiration occurs in all parts of the plant, both green and non-green.
In contrast, photosynthesis occurs only in the green parts of the plant (mainly the leaves), where sunlight, water, and carbon dioxide are used to produce glucose and oxygen. Unlike respiration, which releases energy, photosynthesis stores energy in the form of glucose.

Q5: How do stomata function in gas exchange during photosynthesis and respiration?
Answer: Stomata are tiny pores located on the surface of leaves that play a key role in gas exchange. During photosynthesis, stomata allow carbon dioxide to enter the leaf from the air, which is necessary for the production of glucose. At the same time, oxygen, a by-product of photosynthesis, exits the leaf through the stomata.
In respiration, the stomata also allow oxygen to enter for the breakdown of glucose and the release of energy, while carbon dioxide, a waste product of respiration, exits the plant. The opening and closing of stomata are regulated by guard cells, ensuring that the plant can exchange gases efficiently while minimizing water loss.

Short Answer Question

Q1: What do you mean by animal nutrition?
Ans: Animal nutrition refers to the study of the nutritional needs of animals, which includes:

• The requirement for nutrients essential for growth, maintenance, and reproduction.
• The mode of food intake, which varies among different species.
• The utilisation of food within the body for various physiological processes.

Understanding these aspects is crucial for improving animal health and productivity.

Q2: What is digestion?
Ans: Digestion is the process of breaking down complex components of food, such as carbohydrates, into simpler substances. These simpler substances are then absorbed and assimilated by the body.

Q3: Name different modes of feeding in animals?
Ans: Scraping, chewing, brewing, capturing and swallowing, sucking etc. are the different mode of feeding in animals.

Q4: What are the functions of the tongue in human body?
Ans: The functions of the tongue are as follows:

• Speech: It is essential for talking; it is not possible to articulate words without it.
• Mixing: The tongue mixes saliva with food during chewing, aiding in the swallowing process.
• Taste: Thanks to the presence of taste buds, it identifies various flavours such as sweet and salty.
  Taste Buds

Q5: Name the main organs of digestive system.
Ans: The main organs of digestive system are liver, Gall bladder Stomach, Pancreas, Small intestine, Large intestine, Rectum, Anus. The digestive tract and the associated glands together constitute the digestive system.

Q6: Explain tooth decay?
Ans: Our mouth contains some useful bacteria, but if we do not clean our teeth and mouth after eating, harmful bacteria can also begin to thrive. These harmful bacteria break down the sugars from leftover food and release acids. Over time, these acids gradually damage the teeth and lead to tooth decay.

Q7: Glucose is considered as the source of instant energy, why?
Ans: Glucose is the simplest form of carbohydrate and can be easily broken down to provide energy. This property makes glucose a source of instant energy for the body. Furthermore, glucose mixes directly into the bloodstream, ensuring it is readily available for immediate use by our cells.

Q8: What are secreted inside the stomach?
Ans: Gastric juice is secreted by the walls of the stomach and contains hydrochloric acid (HCl) and pepsin. HCl plays a crucial role in killing germs present in food. After mixing with food, it provides an acidic medium that is essential for activating the pepsin enzyme. Pepsin is responsible for digesting proteins into peptides.

Q9: Explain digestive enzymes?
Ans: There are different types of enzymes which are used for the digestion of different food materials like carbohydrates, fats, protein etc. The process of digestion involves the association of several catalytic organic compounds such as amylase, pepsin, lipase, trypsin etc. These organic compounds are known as digestive enzymes.

Q10: What do you mean by absorption in terms of digestion of food?
Ans: The process of absorption occurs after food has been digested in the stomach. It involves the transfer of nutrients from the food into the blood vessels located in the walls of the intestine. This critical step allows the body to utilize the nutrients for energy and growth.

Q11: Name and explain the type of carbohydrates that can be digested by ruminants but not by humans.
Ans: Cellulose is the type of carbohydrate that can be digested by ruminants but not by humans. Ruminants possess a large, sac-like structure located between the small intestine and large intestine, which is essential for the digestion of cellulose. The cellulose in their food is broken down by the action of specific bacteria that are absent in humans.

Q12: What role does villi performs in the small intestine?
Ans: The villi increase the surface area for the absorption of digested food. Their surface is designed to effectively absorb the digested materials and transfer them into the blood. Once absorbed, these substances are transported via blood vessels to various organs of the body.

Q13: What is rumination?
Ans: Rumination is a process in which partially digested food is regurgitated as small lumps and then chewed again. Animals that engage in this process are known as ruminants.

Q14: How does digestion occur in ruminants grass-eating animals?
Ans: Ruminants quickly swallow grass and store it in a separate part of the stomach called the rumen. Here, the food undergoes partial digestion and is referred to as cud. Later, the cud returns to the mouth in small lumps, and the animal chews it. This process is known as rumination. The cellulose present in grass is digested in the rumen by the action of specific bacteria, which are not found in humans.

Q15: What is the site of production of bile? Which component of the food does it digest?
Ans: Bile is produced in the liver and is stored in a sac-like structure called the gallbladder. It plays an important role in the digestion of fats, acting on them to convert them into a simpler form.

Q16: What happens to the food in stomach of the digestive tract?
Ans: The inner lining of the stomach secretes mucus, hydrochloric acid, and digestive juices. The mucus protects the lining of the stomach. The hydrochloric acid kills many bacteria that enter with food and creates an acidic environment in the stomach. Additionally, the digestive juices break down proteins into simpler substances.

Q17: What happens to the food in large intestine of the digestive tract?
Ans: The food that remains undigested and unabsorbed enters the large intestine from the small intestine. The large intestine is approximately 1.5 metres in length. Its primary function is to absorb water and some salts from the undigested food material.

Long Answer Question

Q1: Can we survive only on raw, leafy vegetables / grass? Discuss.
Ans: Animals, including most bacteria and non-green plants, as well as humans, do not have the ability to synthesize their own food. Therefore, they rely on autotrophs for their food supply, either directly or indirectly. Green plants, such as leafy vegetables and grass, trap solar energy and manufacture their food in the form of glucose. While leafy vegetables and grass are nutritious, they may not provide sufficient energy for human survival alone. Humans require a varied diet that includes proteins and other nutrients that are not typically found in high quantities in raw, leafy vegetables or grass. In conclusion, although leafy vegetables and grass play a vital role in a healthy diet, relying solely on them may not meet all the nutritional needs of humans.

Q2: What happens to the food in small intestine of the digestive tract?
Ans: The small intestine is highly coiled and is about 7.5 metres long. Liver is the largest gland in the body. It secretes bile juice that is stored in a sac called the gall bladder. It digests fats. The pancreas is cream colour red gland secretes pancreatic juice that acts on carbohydrates and proteins and changes them into simpler forms. The carbohydrates get broken into simple sugars such as glucose, fats into fatty acids and glycerol, and proteins into amino acid, she digested food can now pass into the blood vessels in the wall of the intestine having thousands of finger-like villi. The surface of the villi absorbs the digested food materials. The absorbed substances are transported via the blood vessels to different organs of the body.

Q3: Draw a labelled diagram showing digestive system of cow.

Ans : 

Short Answer Questions

Q1: What is the advantage of a distance- time graph?

Ans: Distance-time graphs gives information about the nature of the motion of an object like uniform or uniform motion. Motion of an object can be represented by its distance-time graphs.

Q2: Differentiate between uniform speed and average speed.

Ans: An object is said to be moving with uniform speed if it covers equal distances in equal intervals of time. But when we travel in a vehicle the speed of the vehicle changes from time to time depending upon the conditions existing on the road. In such a situation, the speed is calculated by taking the ratio of the total distance travelled by the vehicle to the total time taken for the journey. This is called the average speed.

Q3: What do you mean by non-uniform speed?

Ans: An object is said to be moving with variable speed or non-uniform speed if it covers equal distances in unequal intervals of time or vice-versa.

Q4: What do you mean by instantaneous speed?

Ans: When we say that the car travels at an average speed of 60 km/h it does not mean that the car would be moving with the speed of 60 km/h throughout the journey. The actual speed of the car may be less than or greater than the average speed at a particular instant of time. The speed of a moving body at any particular instant of time is called instantaneous speed.

Q5: A child is on see-saw, what kind of motion he have and why? Explain.

Ans: On a see-saw child goes up and comes down from mean position and repeats itself .So there is oscillatory motion.

Q6: Explain how in ancient time a day, a month and a year were measured.

Ans: In ancient time the time between one sunrise and the next was called a day. A month was measured from one new moon to the next and a year was fixed as the time taken by the earth to complete one revolution of the sun.

Q7: Define velocity along with its unit.

Ans: Velocity can be defined as the rate of change of displacement.SI unit of velocity is m/s (meter/second Velocity is a vector quantity.

Q8: What are quartz clocks?

Ans: It is a special type of clock or watch which have an electric circuit with one or more cells are called quartz clocks.

Q9: How do we know an object is moving faster compared to the speed of another object?

Ans: By finding the distance travel by a moving body in unit time 1 hr. or 1 sec we know the speed of an object that help us to know which one is moving faster i.e. having greater speed.

Q10: If a car is moving with a speed of 5Km/h on highway then find the distance travelled by the car in 4 hours?

Ans: We know distance travelled by a body = speed X time 

So, distance travelled by the car =5×4=20 km

Q11: Sumit covers a distance of 2.4 Km from his house to reach her college on a scooter. If the scooter has a speed of 6m/sec, calculate the time taken by her to reach the college.

Ans: 

Total distance travelled =2.4km=2.4x1000m=2400m. Speed is 6m/sec 

as time = (Distance/speed) time=2400/6= 400sec.

Q11: How can you say that motion and rest are relative?

Ans: We have observed that the position of stars and planets change while you remain stationary. In reality the earth is moving too. Thus, an object which appears to be at rest, may actually be in motion. Therefore, motion and rest are relative terms.

Q12: Differentiate between circular motion and periodic motion.

Ans: Motion of an object in a circular path is called circular motion eg. Motion of the hands of a clock. But when an object repeats its motion after some time. This type of motion is called periodic motion. E.g. Motion of a pendulum, motion of a child on a swing, motion of the strings of a guitar.

Q13: Give an example when objects undergo combinations of different types of motion?

Ans: The motion of a ball on the ground. Here the ball is rolling on the ground and rotating as well as moving forward on the ground. Thus, the ball undergoes a rectilinear motion as well as rotational motion.

Q14: What is simple pendulum?

Ans: A simple pendulum consists of a small metallic ball or a piece of stone suspended from a rigid stand by a thread .The metallic ball is called the bob of the pendulum.

Q15: What is oscillation of a pendulum?

Ans: One complete to and fro motion of a pendulum from rest position is called one oscillation. The time taken by the pendulum to complete one oscillation is called its time period. It is only depending on the length of the string of pendulum.

Q16: What do you mean by time?

Ans: The interval between two events is called time. Example: The time between one sunrise and the next was called a day. Clocks or watches are the most common time measuring devices. The basic unit of time is a second. Its symbol is s. Larger units of time are minutes (min) and hours (h).

Q17: A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?

Ans: 

Time taken to complete 20 oscillations = 32 s 

Time period of the pendulum = No of oscillations/Total Time taken = 32/20 s = 1.6s

Q18: Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s, calculate the distance between her house and the school.

Ans: 

Distance between her school and house = speed of bicycle X Time taken

= 2m/s × 60s= 1800m

Q19: The distance between two stations is 300 km. A train takes 6 hours to cover this distance. Calculate the speed of the train.

Ans: 

The distance between two stations = 300 km

Time taken by the train to cover that distance = 6 hours

Speed of the train = 300/6 Km/h =50 km/h

Long Answer Questions

Q1: State different types of motion?

Ans: Following are different types of motion:

• Translatory Motion: – In Translatory motion the particle moves from one point in space to another. This motion may be along a straight line or along a curved path.
• Rectilinear motion : Motion along a straight line is called rectilinear motion. Example: A car moving on a straight road
• Curvilinear motion: Motion along a curved path is called curvilinear motion. Example: A car negotiating a curve
• Rotatory Motion : In rotatory motion, the particles of the body describe concentric circles about the axis of motion
• Vibratory Motion: In vibratory motion the particles move to and fro about a fixed point.

Q2: A simple pendulum takes 15 seconds to complete 5 oscillations. What is the time period of pendulum?

Ans: 

The time taken by pendulum to complete 1 oscillation is called time period

The time taken by pendulum to complete 5 oscillation = 15sec

The time taken by pendulum to complete 1 oscillation = 15/5= 3 sec

So time period = 3 sec

Q3: The odometer of a car reads 57321.0 km when the clock shows the time 08:30 AM. What is the distance moved by the car, if at 08:50 AM, the odometer reading has changed to 57336.0 km? Calculate the speed of the car in km/min during this time. Express the speed in km/h also.

Ans: 

Initial reading of car odometer= 57321.0 km

Final reading of car odometer= 57336.0 km

Time at the time of Initial reading= 08:30 AM

Time at the time of Initial reading= 08:50 AM

Distance travelled by the car = 57336.0 km – 57321.0 km 

= 15 Km

Time taken by the car to cover distance = 08:50 AM -08:30 AM

= 20 m

Speed of the car in Km/m = 15 km/20m

= .75 Km/m

Speed of the car in Km/h = 15 km/20m X 60

= 45 Km/h

Q5: A car moves with a speed of 40 km/h for 15 minutes and then with a speed of 60 km/h for the next 15 minutes. The total distance covered by the car is:

Ans: 

Distance covered by the car with a speed of 40 km/h in 15 minutes = Speed * Time 

= (40 Km/h /60 minutes) * 15 minute 

= 10 Km 

Distance covered by the car with a speed of 40 km/h in 15 minutes = Speed * Time 

= (60 Km/h /60 minutes) * 15 minute 

= 15 Km

Total distance covered by the car =(10 + 15 )km = 25 Km

Short Questions and Answers

Q1: Define heat.
Ans: Heat is a form of energy which produces a sensation of warmth and flows when there is a temperature difference between two bodies.  It is measured in joules or calories.

Q2: Define temperature. What is its unit?
Ans:  A reliable measure of the hotness of an object is its temperature. Temperature is measured by a device called a thermometer. The unit of temperature is degree Celsius (°C), Fahrenheit, and Kelvin (SI unit).

Q3: What is the use of the maximum-minimum thermometer?
Ans: The maximum-minimum thermometer is used to measure the highest and lowest temperatures of a place in a day. It is commonly used in weather stations to track daily temperature variations. This thermometer helps in understanding temperature fluctuations, which is essential for weather forecasting and analysis.

Max-min Thermometer

Q4: : What is conduction?
Ans: Heat flows from a hotter object to a colder object. The process by which heat is transferred from the hotter end to the colder end of an object is known as conduction.

Q5: Why conduction is only possible in solids?
Ans: In solids, generally, the heat is transferred by the process of conduction because particles of solids are closely packed, and heat is transferred from the hotter end to the colder end of an object.

Q6: How does the heat from the sun reach us?
Ans:  Heat from the sun reaches us by radiation, which does not require a medium to transfer heat. Unlike conduction (which occurs in solids) and convection (which occurs in liquids and gases), radiation can transfer heat even through the vacuum of space

Q7: Explain how water is heated by convection.

Ans: The water is a poor conductor of heat, so do not heat it by conduction. When water is heated, the water becomes lighter. Hot water rises up. The cold water from the sides moves down towards the source of heat. This water also gets hot and rises upward, and water from the sides moves down. This process continues till the whole water gets heated. This mode of heat transfer is known as convection.

Q8: Differentiate between conductor and insulators?
Ans: The materials which allow heat to pass through them easily are conductors of heat. For example, aluminum, iron, and copper The materials that do not allow heat to pass through them easily are poor conductors of heat, known as insulators, such as plastic and wood.

Q9: Explain land breeze.
Ans: The water cools down more slowly at night than the land. So, the cool air from the land moves towards the sea. This is called the land breeze.

Q10: Explain sea breeze.
Ans: During the day, the land gets heated faster than the water. The air over the land becomes hotter and rises up. The sea’s cooler air rushes towards the land to take its place. The warm air from the land moves towards the sea to complete the cycle. The air from the sea is called the sea breeze.

Long Questions and Answers

Q1: How does heat transfer take place in solids, liquids, and gases?
Ans: Heat can be transferred in three different ways depending on the medium:

Conduction (Solids)

• In solids, heat travels from one particle to another without movement of the particles.
• Example: A metal spoon gets hot when placed in a cup of tea.

Convection (Liquids & Gases)

• In liquids and gases, heat moves through rising hot particles and falling cold particles.
• Example: Boiling water in a pan shows upward movement of hot water and downward movement of cold water.

Radiation (Without Medium)

• Heat can also be transferred without any medium in the form of rays.
• Example: Heat from the Sun reaches Earth through space by radiation.

Thus, different materials transfer heat in different ways, and understanding these helps in designing better insulators and conductors.

Q2: State similarities between the laboratory thermometer and the clinical thermometer.

Ans: Similarities between laboratory thermometer and clinical thermometer are :

• Both are used to measure temperature.
• Both typically use mercury or digital technology to display readings.
• Both require careful handling to ensure accurate readings.
• Both thermometers have a scale marked in degrees Celsius.

Q3: Why do coastal areas experience land breeze and sea breeze?

Ans: In coastal areas, the movement of air between land and sea causes land breeze and sea breeze.

1. Sea Breeze (Daytime)
   • During the day, the land heats up faster than the sea.
   • The air above the land becomes hot and rises, while cooler air from the sea moves in to take its place.
   • This movement of air from the sea to the land is called sea breeze.
2. Land Breeze (Nighttime)
   • At night, the land cools down faster than the sea.
   • The air above the sea remains warmer and rises, and the cooler air from the land moves towards the sea.
   • This movement of air from the land to the sea is called land breeze.

These breezes help moderate temperatures in coastal areas, making them more comfortable.

Short Questions and Answers

Q1: What is adolescence?
Ans: Adolescence is the stage of growth and development between childhood and adulthood, typically occurring between the ages of 10 and 19. It involves rapid physical, emotional, and behavioral changes.

Q2: At what age does adolescence generally start?
Ans: Adolescence generally starts around the age of 10 years.

Q3: What is puberty?
Ans: Puberty is the stage in adolescence when the body undergoes external and internal changes to develop into an adult capable of reproduction.

Q4: What is the role of hormones during adolescence?
Ans: Hormones regulate various aspects of growth and development during adolescence, influencing physical, emotional, and behavioral changes.

Q5: What are secondary sexual characteristics?
Ans: Secondary sexual characteristics are traits that help distinguish males from females, like the development of breasts in girls or facial hair in boys, which mark the onset of puberty.

Q6: How does the voice change during adolescence in boys?
Ans: In adolescent boys, the voice box grows, leading to a hoarse voice. This is visible as the development of the Adam’s apple.

Q7: What is menstruation, and when does it start?
Ans: Menstruation is the process where adolescent girls experience a monthly discharge of blood from the uterus, marking the onset of reproductive capability, typically starting around the age of 12.

Q8: Why do acne and pimples appear during adolescence?
Ans: Acne and pimples appear during adolescence due to an increase in oily secretions from the skin, which can clog pores and lead to infections.

Q9: How do boys and girls differ in terms of body changes during adolescence?
Ans: Boys typically experience the development of a deeper voice, facial hair, and broader shoulders. Girls experience changes like breast development and wider hips, along with a menstrual cycle.

Q10: What is the importance of a healthy diet during adolescence?
Ans: A healthy diet is crucial during adolescence as it supports rapid growth and development, providing essential nutrients like proteins, vitamins, and minerals for optimal physical and mental health.

Long Questions and Answers

Q1: Discuss the physical changes that occur in both boys and girls during adolescence.
Ans: During adolescence, both boys and girls experience significant physical changes. Boys typically undergo growth in height, develop broader shoulders, and experience the growth of facial hair, such as moustaches and beards. Their voices become deeper due to the growth of the voice box (Adam’s apple). Girls also grow in height and experience the development of breasts and wider hips. Both boys and girls develop hair in the armpits and pubic regions. Additionally, boys may develop chest and back hair, although this is not universal. Pimples and acne are common for both genders due to increased oily secretions from the skin.

Q2: Explain the concept of puberty and its relation to reproductive health.
Ans: Puberty is a critical stage in adolescence where the body undergoes both external and internal changes that prepare it for reproduction. It marks the transition from childhood to adulthood. In girls, puberty is associated with the start of menstruation, which is a key indicator of reproductive capability. In boys, puberty involves the development of secondary sexual characteristics like facial hair and a deeper voice, signaling the body’s readiness for reproduction. Puberty involves hormonal changes that drive these physical transformations, preparing individuals for adulthood.

Q3: How do emotional and behavioral changes affect adolescents, and what steps can they take for positive growth?
Ans: Adolescents undergo significant emotional and behavioral changes due to the surge in hormones. They may experience mood swings, increased sensitivity, and curiosity, leading to both positive and negative behavior. These emotional changes can lead to stronger feelings of empathy, social engagement, and self-exploration, but may also cause confusion and impulsive decisions. To ensure positive growth, adolescents can engage in various activities like sports, music, or volunteering, which help them channel their emotions productively. Seeking guidance from trusted adults and maintaining healthy social relationships also aid in emotional stability.

Q4: What are the challenges and benefits of maintaining good hygiene during adolescence?
Ans: During adolescence, personal hygiene becomes increasingly important as the body undergoes significant changes. Good hygiene, especially in areas like the armpits, face, and pubic region, helps prevent infections and body odor. Girls, in particular, must maintain menstrual hygiene to ensure comfort and health. While maintaining hygiene can be challenging due to the increase in sweat and body changes, it is essential to prevent skin conditions like acne and other infections. Using sanitary pads during menstruation, regularly washing the face, and wearing clean clothes are simple yet effective ways to maintain hygiene and support overall health.

Q5: Discuss the risks associated with substance abuse during adolescence and how to avoid them.
Ans: Adolescence is a period marked by curiosity and peer pressure, which can make adolescents more susceptible to trying harmful substances like tobacco, alcohol, and drugs. These substances can have serious effects on physical and mental health, leading to addiction, lung damage, memory loss, and other severe health issues. It is important for adolescents to understand the risks of substance abuse and to make informed decisions. They can avoid these risks by saying “NO” to peer pressure, seeking support from family and teachers, and engaging in healthy activities like sports and hobbies. Educating adolescents about the harmful effects of substances and providing a supportive environment helps them make healthier choices.

Short Answer Questions

Q1: Explain physical reaction along with examples.
Ans : A change in which a substance undergoes a change in its physical properties is called a physical change. For example; melting of ice.
Q2: Explain chemical reaction along with examples.
Ans : A change in which one or more new substances are formed is called a chemical reaction. For example; rusting of iron.
Q3: Differentiate between physical and chemical reactions.
Ans : Physical ReactionChemical Reaction A change in the physical properties of a substance. A change in which one or more new substances are formed. A physical change is generally reversible. A chemical change is generally irreversible. 

Q4: State the condition necessary for the occurrence of any reactant.
Ans : For the occurrence of any reaction, the following condition is necessary:

• The molecules or atoms of the reactants must collide with each other.
• This collision is essential to break old bonds and form new ones.

Q5: Why new products are formed in a chemical reaction?
Ans : New products are formed in a chemical reaction due to the following reasons:

• The old bonds between atoms in the reactants are broken.
• New bonds are created, leading to the formation of different substances.
• The resulting products have different properties compared to the original reactants.

Q6: Explain the process of rusting.
Ans: The process of rusting occurs when iron is exposed to damp air or water for a long time. This results in a reddish-brown flaky substance known as rust. The key steps in rusting are:

• Iron reacts with oxygen from the air.
• This reaction requires the presence of water or moisture.
• The outcome of this reaction is a compound called iron oxide.

Rusting is accelerated in humid conditions, making it a significant issue for iron objects.

Q7: How can we prevent rusting?
Ans: To prevent rusting, it is essential to keep iron, water, and oxygen apart. Here are some effective methods:

• Apply a coat of paint or grease regularly to create a barrier.
• Use wax or oil coatings, especially for vehicles.
• Keep tools and equipment dry; wipe them down after use.
• Store items in a dry place to avoid moisture.

Q8: Setting of curd is regarded as a chemical change, explain why?
Ans: The setting of curd is considered a chemical change for the following reasons:

• The original substance, milk, cannot be recovered after curd is formed.
• Curd has distinct taste, smell, and chemical properties compared to milk.
• New substances are created during the process, indicating a transformation.

Q9: What happens when baking soda is treated with vinegar?
Ans: When baking soda is mixed with vinegar, a reaction occurs that produces a hissing sound and bubbles. This is due to the formation of carbon dioxide gas. The chemical equation for this reaction is:

• Vinegar (Acetic acid) + Baking soda (Sodium hydrogen carbonate) → Carbon dioxide + other substances.

The bubbles you see are the carbon dioxide gas being released during the reaction.

Q10: What happens when a piece of iron metal is placed in copper sulphate solution?
Ans: When iron is placed in Copper sulphate solution, the iron is coated with a brown coloured substance “copper” and CuSO₄ solution changes from blue to light green. This is due to iron displacing copper as it is more reactive than copper.

Q11: Explain the changes occuring in burning of candle.
Ans: When a candle burns, it undergoes both physical and chemical changes:

• The wax melts as it heats up, which is a physical change because it can solidify again when cooled.
• As the candle burns, it produces light and gases, such as carbon dioxide, indicating a chemical change due to the combustion of the wick.

Q12: Baking soda is mixed with lemon juice, bubbles are formed with the evolution of gas, explain the changes occurred here.
Ans: When baking soda is mixed with lemon juice, a chemical reaction occurs, resulting in the formation of bubbles. This happens because:

• A new substance, carbon dioxide, is produced during the reaction.
• The release of gas creates visible bubbles.
• This process is an example of a chemical change as new substances are formed.

Q13: Name some of the process in which both chemical and physical changes take place.
Ans: One example of a process that involves both chemical and physical changes is the burning of wood:

• The moisture in the wood turns to vapor when heated, which is a physical change.
• The actual burning produces carbon dioxide and other products, indicating a chemical change.

Q14: Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.
Ans: Burning of wood produces ash and smoke. Hence the properties of wood are changed and new substances are formed. So, it is a chemical reaction. When a log of wood is cut into small pieces,there is no new substance formed. Each small piece bears the properties of wood. So, its a physical change.Obviously, burning and cutting of wood are two different types of changes.

Q15: Explain how painting of an iron rod prevents it from rusting.
Ans: To prevent rusting, it is essential to stop iron from contacting both air and moisture. Painting an iron gate achieves this by:

• Creating a protective barrier that blocks air and moisture.
• Reducing the chances of rust formation.
• Ensuring the iron remains dry and free from corrosive elements.

Regular maintenance of the paint layer is important to keep the iron protected. 

Q16: A part from new products, many other things accompany a chemical change, what are those things?
Ans : Part from new products, many other things accompany a chemical change, those things are:

• Heat, light or any other radiation may be given off or absorbed.
• Change in smell may take place.
• Sound may be produced.
• Change in colour may take place.
• A gas may be formed

Q17: Burning of any substance is the chemical change. Discuss.
Ans: Burning of any substance is a chemical change. Burning involves a series of changes:

• Heat is always produced.
• The old bonds in the reactants are broken.
• New bonds are formed, leading to new products.
• The properties of these new products differ from the original substances.

Thus, burning is a clear example of a chemical change. 

Q18: State Four characteristics which are included in the physical properties of matter.
Ans: Physical properties of matter include the following characteristics:

• Shape: The form or outline of an object.
• Size: The dimensions or magnitude of an object.
• Colour: The visual perception of light reflected from an object.
• State: The physical form of matter, such as solid, liquid, or gas.

Q19: Why formation of manure from leaves is a chemical change?
Ans: The formation of manure from leaves is a chemical change because:

• It produces a new substance with a different composition.
• The original leaves undergo a transformation that alters their chemical structure.

Q20: Why cutting of wood is a physical change?
Ans: Cutting of wood is classified as a physical change for the following reasons:

• The identity of the wood remains the same.
• Its composition does not change.
• No new substances are formed during the process.

Thus, cutting wood is a reversible change that affects its shape and sizebut not its fundamental properties. 

Long Answer Questions

Q1: Explain the physical and chemical processes along with examples.
Ans: A change in which a substance undergoes a change in its physical properties is called physical change, physical properties involves shape, size, colour and state of a substance. It is generally reversible; in physical change no new substance is formed. For example: evaporation, condensation etc.
A change in which one or more new substances are formed is called chemical change. Chemical change is irreversible. It is also called chemical reaction; in this type of change a new substance is formed. Example—Burning of coal, photosynthesis.
The difference between physical change and chemical change is as follows-Physical change
(1) No new substance is formed. A substance undergoes a change in its physical properties.
(2) Physical change is generally reversible.
Example—Melting of ice, lighting of bulb Chemical Change
(1) One or more new substances are formed by chemical reaction.
(2) Chemical change is irreversible.
Example—burning of coal, photosynthesis

Q2: Explain the process of rusting of iron, and measures to prevent the same.
Ans: 

The process of rusting occurs when iron reacts with oxygen and water, forming a reddish-brown substance known as rust (iron oxide). This reaction is accelerated in humid conditions where moisture is abundant. To prevent rusting, consider the following methods:

• Galvanisation: This involves coating iron with a layer of zinc, which protects it from moisture and oxygen.
• Painting or Greasing: Applying a coat of paint or grease creates a barrier that prevents contact with air and water.
• Using Stainless Steel: Stainless steel, made by mixing iron with chromium and other metals, is resistant to rust.

Regular maintenance of protective coatings is essential to ensure long-lasting protection against rusting. 

Q3: Why chemical changes are very important in our life?
Ans: A chemical change occurs when the composition of a substance is altered, resulting in the formation of one or more new substances. This process is essential in our daily lives for several reasons:

• New substances are created through chemical changes, such as during the digestion of food and the ripening of fruits.
• Medicines are produced as a result of complex chemical reactions.
• Many useful materials, including plastics and detergents, are formed through chemical processes.
• Every new material discovered is linked to the study of chemical changes.

In summary, chemical changes are vital as they lead to the creation of essential substances and materials that support life and industry. 

Q4: Rusting of an iron object is faster is coastal areas than in desert area. Explain why?
Ans: Rusting of an iron object occurs more rapidly in coastal areas than in desert regions due to the following reasons:

• Coastal areas have higher levels of moisture in the air because of the nearby sea.
• Deserts, on the other hand, have dry air with little to no moisture.
• Both air and moisture are essential for rusting to take place.
• Thus, the increased humidity in coastal areas leads to faster rusting compared to the arid conditions of deserts.

Short Questions and Answers

Q1: What is malleability?
Ans: Malleability is the property of materials by which they can be beaten or hammered into thin sheets. Metals like copper, aluminium, and iron possess malleability.

Q2: What happens when metals like copper and aluminium are beaten with a hammer?
Ans: Metals like copper and aluminium become flattened when beaten with a hammer, demonstrating their malleability.

Q3: What is ductility?
Ans: Ductility is the property of materials that allows them to be drawn into wires. Metals such as gold and copper are highly ductile.

Q4: What is sonority in metals?
Ans: Sonority is the property of metals to produce a ringing sound when struck. Metals like iron and steel are sonorous.

Q5: Why are metals used for cooking utensils?
Ans: Metals are good conductors of heat, which makes them ideal for cooking utensils as they quickly transfer heat to food.

Q6: What is corrosion?
Ans: Corrosion is the gradual deterioration of metals due to reactions with air, water, or other substances. For example, iron rusts when exposed to moist air.

Q7: What happens when metals react with oxygen?
Ans: When metals react with oxygen, they form metal oxides, which are usually basic in nature.

Q8: Why are metals like iron and copper used in electrical wiring?
Ans: Metals like iron and copper are good conductors of electricity, making them ideal for use in electrical wiring.

Q9: Why is sodium stored in kerosene?
Ans: Sodium reacts vigorously with water and oxygen, generating a lot of heat. Storing sodium in kerosene prevents it from reacting with moisture and air.

Q10: What is the importance of metals and non-metals in everyday life?
Ans: Metals and non-metals play vital roles in daily life. Metals are used in construction, electrical devices, and tools, while non-metals like oxygen and nitrogen are essential for life and plant growth.

Long Questions and Answers:

Q1: Describe the physical properties of metals and how they differ from non-metals.
Ans: Metals generally exhibit properties like metallic lustre, malleability, ductility, sonority, and high conductivity of heat and electricity. Non-metals, on the other hand, are generally non-lustrous, brittle, and poor conductors of heat and electricity. Metals can be hammered into sheets (malleable) and drawn into wires (ductile), whereas non-metals lack these properties. Non-metals also form acidic oxides when they react with oxygen, while metals typically form basic oxides.

Q2: How does the reaction of metals and non-metals with oxygen differ?
Ans: Metals generally react with oxygen to form basic metal oxides, such as iron oxide (rust), which is alkaline in nature. Non-metals, on the other hand, form acidic oxides when they react with oxygen, such as sulfur dioxide, which forms sulfurous acid when dissolved in water. This difference in reactions is key to understanding the nature of oxides formed by metals and non-metals.

Q3: Explain the process of rusting and how it can be prevented.
Ans: Rusting is the process where iron reacts with oxygen and water to form iron oxide (rust), which causes the iron to deteriorate. Rusting can be prevented by methods such as painting, oiling, greasing, or applying a protective layer of zinc (galvanization). These methods protect the iron from direct exposure to air and water, thus preventing corrosion.

Q4: What are the applications of metals in daily life?
Ans: Metals have numerous applications in daily life due to their distinct properties. For instance, metals like copper and aluminium are used for electrical wiring due to their excellent conductivity. Iron and steel are used in construction and making tools due to their strength and malleability. Precious metals like gold and silver are used in jewelry, while aluminium is used in food packaging materials due to its malleability and low cost. Metals are also used in the manufacturing of machinery, vehicles, and electronics.

Q5: Discuss the uses of non-metals in everyday life.
Ans: Non-metals like oxygen are essential for respiration, making them crucial for life. Nitrogen is used in fertilizers to enhance plant growth. Carbon is an important element in organic molecules and fuels. Chlorine is used in water purification, while iodine is used as an antiseptic for wounds. Non-metals are also found in medicines, food preservation, and industrial applications like rubber manufacturing and water treatment.

Short Answer Questions:

Q1: What is a torchlight?
Answer: A torchlight is a portable device that produces light, commonly used to see in the dark.Torchlight

Q2: What is the function of the electric cell in a torchlight?
Answer: The electric cell provides the energy needed to make the lamp glow by allowing current to flow from the positive to the negative terminal.

Q3: How does an electric circuit work?
Answer: An electric circuit is a complete path that allows current to flow from a power source (like a cell) through a device (like a lamp) and back, making the device work.

CircuitQ4: What is the difference between an electric cell and a battery?
Answer: An electric cell is a single source of electrical energy, while a battery is a combination of two or more cells connected together to provide more energy.

Q5: What is an incandescent lamp?
Answer: An incandescent lamp has a filament inside that glows when electric current passes through it, producing light.

Q6: What is the function of a switch in a circuit?
Answer: A switch controls the flow of current by either completing (closing) or breaking (opening) the circuit.

Q7: What is the purpose of using insulators in electrical circuits?
Answer: Insulators prevent the flow of electric current and are used to cover wires and make switches and plugs to ensure safety.

Q8: What is a circuit diagram?
Answer: A circuit diagram is a drawing that uses standard symbols to represent the components of an electrical circuit.

Circuit DiagramQ9: What is the role of a filament in an incandescent lamp?
Answer: The filament inside the incandescent lamp glows when heated by the electric current, producing light.

Q10: What are the types of electricity used in devices?
Answer: The two main types of electricity are Direct Current (DC), used in devices like torchlights and phones, and Alternating Current (AC), used for larger appliances.Long Answer Questions:

Q1: Explain how an electric cell works in providing energy to a device.

Answer:  

•  An electric cell is a source of electrical energy. 
•  It has two terminals: a positive (+) terminal and a negative (-) terminal. 

Electric Cell

•  These two terminals are connected by a circuit. 
•  Inside the cell, a chemical reaction occurs between the materials inside the cell. 
•  This chemical reaction releases electrons (tiny charged particles) that move from the negative terminal to the positive terminal, creating an electric current. 
•  This current flows through the wires of the circuit and powers the devices connected to it, like lamps, radios, clocks, or remote controls. 
•  The flow of current from the electric cell provides the energy needed for these devices to work. 

Q2: Describe the structure and working of an LED lamp.

Answer: 

•  An LED lamp is different from traditional lamps like incandescent or fluorescent lamps. 
•  It does not have a filament, but instead uses a special material called a diode to produce light. 
•  The LED lamp has two terminals: one longer (positive terminal) and one shorter (negative terminal). 
•  The lamp is designed to glow when the positive terminal of the lamp is connected to the positive side of a battery or power source, and the negative terminal is connected to the negative side. 
•  When current flows through the LED, it moves in only one direction because LEDs only work when the current is going from the positive to the negative terminal. 
•  This makes LEDs more efficient, meaning they use less energy to produce light and last longer than regular bulbs. 
•  Since there is no filament, LED lamps are less likely to break or burn out, which makes them more durable. 

Q3: How does a simple electrical circuit work to make a lamp glow?

Answer: 

• A simple electrical circuit consists of a few key parts: an electric cell (like a battery), a lamp, and wires.
• When the switch in the circuit is in the “on” position, it allows electricity to flow from the positive terminal of the cell through the wires and into the lamp.
• Inside the lamp, there is a filament (a thin wire), and when electricity passes through the filament, it heats up and starts to glow.
• This produces light.
• If the switch is turned off, the circuit becomes incomplete, and the electric current cannot flow, so the lamp will not glow.
• The switch is used to either allow or stop the flow of electricity, controlling when the lamp is on or off.

Q4: What are the roles of conductors and insulators in electrical circuits?

Answer: In an electrical circuit, conductors and insulators play important roles:

Conductors vs Insulators

• Conductors are materials that allow electricity to flow through them easily. Metals like copper, silver, and aluminum are good conductors. They are used in the wires that connect different parts of an electrical circuit because they let the electric current pass through them without resistance.
• Insulators, on the other hand, are materials that do not allow electricity to flow. They protect us from electric shocks. Common insulators include plastic, rubber, and wood. These materials are used to cover wires, make electrical switches, and create plug tops. They make sure that the current stays inside the wires and does not harm us or cause short circuits.

In simple terms, conductors let electricity flow, while insulators keep electricity safely contained within the circuit.

Q5: Discuss the importance of switches in electrical circuits.

Answer: 

• A switch is an important device in electrical circuits because it helps control the flow of electricity.
• The switch acts like a gate for the electric current.
• When the switch is in the “on” position, it closes the circuit, allowing electricity to flow through and power the connected device, such as a lamp, fan, or television.
• This makes the device work.
• When the switch is in the “off” position, it opens the circuit, which stops the flow of electricity.
• As a result, the device is turned off.
• Switches are essential for turning electrical devices on and off safely and efficiently.
• Without switches, you would have to disconnect wires every time you want to turn something off, which would be impractical and unsafe.
• Therefore, switches make electrical circuits safer and easier to use, as they give us control over the devices that run on electricity.