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NCERT Textbook: Electricity: Circuits and their Components
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Page 1 Electricity: Circuits and their Components 3 Nihal and his classmates were excited for their school trip to the Bhakra Nangal Dam. There they would visit the hydroelectric power house where the force of falling water was used to generate electricity. They also looked forward to the free 13 kilometre- train ride from Nangal in Punjab to Bhakra in Himachal Pradesh, along the beautiful Sutlej river and through the Shivalik hills. Prior to the trip, Nihal and his classmates were given a group assignment to prepare a presentation on the uses of electricity. They began by looking around their houses, then their school, followed by their neighbourhood, their city, and ?? nally they searched the internet. To their astonishment, their list kept growing. They decided to organise the uses under di?? erent headings. Entertainment Television, radio, _______________ Communication Mobile phone, Internet, _______________ Others Water pump, crane, computer , _______________ Lighting Homes, o?? ces, streets, markets, factories, _______________ Cooking Electric kettle, mixer grinder, toaster , oven, microwave, _______________ Transportation Train, bus, car, scooter , lift, escalator , _______________ Heating and Cooling Fan, room heater , immersion rod, geyser , refrigerator , air conditioner , _____ Chapter 3.indd 23 Chapter 3.indd 23 4/3/2025 4:51:22 PM 4/3/2025 4:51:22 PM Reprint 2026-27 Page 2 Electricity: Circuits and their Components 3 Nihal and his classmates were excited for their school trip to the Bhakra Nangal Dam. There they would visit the hydroelectric power house where the force of falling water was used to generate electricity. They also looked forward to the free 13 kilometre- train ride from Nangal in Punjab to Bhakra in Himachal Pradesh, along the beautiful Sutlej river and through the Shivalik hills. Prior to the trip, Nihal and his classmates were given a group assignment to prepare a presentation on the uses of electricity. They began by looking around their houses, then their school, followed by their neighbourhood, their city, and ?? nally they searched the internet. To their astonishment, their list kept growing. They decided to organise the uses under di?? erent headings. Entertainment Television, radio, _______________ Communication Mobile phone, Internet, _______________ Others Water pump, crane, computer , _______________ Lighting Homes, o?? ces, streets, markets, factories, _______________ Cooking Electric kettle, mixer grinder, toaster , oven, microwave, _______________ Transportation Train, bus, car, scooter , lift, escalator , _______________ Heating and Cooling Fan, room heater , immersion rod, geyser , refrigerator , air conditioner , _____ Chapter 3.indd 23 Chapter 3.indd 23 4/3/2025 4:51:22 PM 4/3/2025 4:51:22 PM Reprint 2026-27 Curiosity | Textbook of Science | Grade 7 24 Can you help Nihal by adding some more uses to his lists? Also, suggest some other ways of grouping the uses of electricity. We use electricity all the time, so let us learn something more about electricity. You have learnt earlier that electricity is generated in multiple ways?—?by windmills, by using wind energy, by solar panels capturing the Sun’s energy, by falling water and by using natural gas or coal (in the chapter ‘Nature’s Treasures’ in the Grade 6 Science textbook Curiosity). The electric supply from these sources reaches our homes and factories via wires. For example, at home we plug in various devices to the electrical sockets in the wall. However, to learn about electricity, we will focus on a portable source of electricity that most of us may have used. Let us start with its use in a common device like a torchlight. Caution —?The danger signs on electric poles and other appliances warn people that electricity can be dangerous if not carefully handled. Never ever perform experiments with power supply at your home or school. Even electricity from portable generators can be dangerous. Use only batteries or cells, like those in torchlights, wall clocks, radios, or remotes, for experiments with electricity. 3.1 A Torchlight You might have used a torchlight, also called a torch or a ??ashlight. Activity 3.1: Let us explore ?? Take a torchlight similar to the one shown in Fig. 3.1. ?? Observe it carefully. Do you notice a lamp? And a switch? ?? Slide its switch and observe. Does the torch lamp glow? ?? Now slide the switch back to its original position and observe the torch lamp. You might have noticed that in one position of the switch, the torch lamp glows and in the other position the lamp does not glow. ?? Now, open the torchlight. What do you ??nd inside? Inside the torchlight, you may ??nd two or more electric cells. Why does the torch lamp glow in one position of its switch? Fig. 3.1: A torchlight Chapter 3.indd 24 Chapter 3.indd 24 09-09-2025 11.29.52 AM 09-09-2025 11.29.52 AM Reprint 2026-27 Page 3 Electricity: Circuits and their Components 3 Nihal and his classmates were excited for their school trip to the Bhakra Nangal Dam. There they would visit the hydroelectric power house where the force of falling water was used to generate electricity. They also looked forward to the free 13 kilometre- train ride from Nangal in Punjab to Bhakra in Himachal Pradesh, along the beautiful Sutlej river and through the Shivalik hills. Prior to the trip, Nihal and his classmates were given a group assignment to prepare a presentation on the uses of electricity. They began by looking around their houses, then their school, followed by their neighbourhood, their city, and ?? nally they searched the internet. To their astonishment, their list kept growing. They decided to organise the uses under di?? erent headings. Entertainment Television, radio, _______________ Communication Mobile phone, Internet, _______________ Others Water pump, crane, computer , _______________ Lighting Homes, o?? ces, streets, markets, factories, _______________ Cooking Electric kettle, mixer grinder, toaster , oven, microwave, _______________ Transportation Train, bus, car, scooter , lift, escalator , _______________ Heating and Cooling Fan, room heater , immersion rod, geyser , refrigerator , air conditioner , _____ Chapter 3.indd 23 Chapter 3.indd 23 4/3/2025 4:51:22 PM 4/3/2025 4:51:22 PM Reprint 2026-27 Curiosity | Textbook of Science | Grade 7 24 Can you help Nihal by adding some more uses to his lists? Also, suggest some other ways of grouping the uses of electricity. We use electricity all the time, so let us learn something more about electricity. You have learnt earlier that electricity is generated in multiple ways?—?by windmills, by using wind energy, by solar panels capturing the Sun’s energy, by falling water and by using natural gas or coal (in the chapter ‘Nature’s Treasures’ in the Grade 6 Science textbook Curiosity). The electric supply from these sources reaches our homes and factories via wires. For example, at home we plug in various devices to the electrical sockets in the wall. However, to learn about electricity, we will focus on a portable source of electricity that most of us may have used. Let us start with its use in a common device like a torchlight. Caution —?The danger signs on electric poles and other appliances warn people that electricity can be dangerous if not carefully handled. Never ever perform experiments with power supply at your home or school. Even electricity from portable generators can be dangerous. Use only batteries or cells, like those in torchlights, wall clocks, radios, or remotes, for experiments with electricity. 3.1 A Torchlight You might have used a torchlight, also called a torch or a ??ashlight. Activity 3.1: Let us explore ?? Take a torchlight similar to the one shown in Fig. 3.1. ?? Observe it carefully. Do you notice a lamp? And a switch? ?? Slide its switch and observe. Does the torch lamp glow? ?? Now slide the switch back to its original position and observe the torch lamp. You might have noticed that in one position of the switch, the torch lamp glows and in the other position the lamp does not glow. ?? Now, open the torchlight. What do you ??nd inside? Inside the torchlight, you may ??nd two or more electric cells. Why does the torch lamp glow in one position of its switch? Fig. 3.1: A torchlight Chapter 3.indd 24 Chapter 3.indd 24 09-09-2025 11.29.52 AM 09-09-2025 11.29.52 AM Reprint 2026-27 Electricity: Circuits and their Components 25 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit To understand how a torch works, let us ?? rst ?? nd out about its components. 3.2.1 Electric cell Activity 3.2: Let us observe ?? Take an electric cell, turn it around and look at it carefully (Fig. 3.2). Do you notice a positive (+) sign and a negative (–) sign marked on the electric cell? Do you also notice that it has a small protruding metal cap on one side and a ?? at metal disc on the other side? All electric cells have two terminals; one is called positive (+?ve) while the other is negative (–?ve). The metal cap is the positive terminal of the electric cell and the metal disc is the negative terminal. The electric cell is a portable source of electrical energy . 3.2.2 Battery Activity 3.3: Let us experiment ?? Take a torch which uses two cells. Open its cell compartment and take out the cells. ?? Put the cells back in a di?? erent order. Also, try reversing the direction of one cell. Then, slide the switch and check whether the lamp glows in each case. ?? Check the order in which the cells were placed in the torch when the lamp glows. The lamp glows when the cells are placed in the order as shown in Fig. 3.3. Notice how the terminals of the two cells are connected. The positive terminal of one cell is connected to the negative terminal of the next cell. Such a combination of two or more cells is called a battery. (a) (b) Fig. 3.3: A battery made up of (a) two cells (b) four cells Fig. 3.2: An electric cell Positive terminal Negative terminal In a torch, we generally use more than one cell. Are those placed in any particular order? Chapter 3.indd 25 Chapter 3.indd 25 4/3/2025 4:51:26 PM 4/3/2025 4:51:26 PM Reprint 2026-27 Page 4 Electricity: Circuits and their Components 3 Nihal and his classmates were excited for their school trip to the Bhakra Nangal Dam. There they would visit the hydroelectric power house where the force of falling water was used to generate electricity. They also looked forward to the free 13 kilometre- train ride from Nangal in Punjab to Bhakra in Himachal Pradesh, along the beautiful Sutlej river and through the Shivalik hills. Prior to the trip, Nihal and his classmates were given a group assignment to prepare a presentation on the uses of electricity. They began by looking around their houses, then their school, followed by their neighbourhood, their city, and ?? nally they searched the internet. To their astonishment, their list kept growing. They decided to organise the uses under di?? erent headings. Entertainment Television, radio, _______________ Communication Mobile phone, Internet, _______________ Others Water pump, crane, computer , _______________ Lighting Homes, o?? ces, streets, markets, factories, _______________ Cooking Electric kettle, mixer grinder, toaster , oven, microwave, _______________ Transportation Train, bus, car, scooter , lift, escalator , _______________ Heating and Cooling Fan, room heater , immersion rod, geyser , refrigerator , air conditioner , _____ Chapter 3.indd 23 Chapter 3.indd 23 4/3/2025 4:51:22 PM 4/3/2025 4:51:22 PM Reprint 2026-27 Curiosity | Textbook of Science | Grade 7 24 Can you help Nihal by adding some more uses to his lists? Also, suggest some other ways of grouping the uses of electricity. We use electricity all the time, so let us learn something more about electricity. You have learnt earlier that electricity is generated in multiple ways?—?by windmills, by using wind energy, by solar panels capturing the Sun’s energy, by falling water and by using natural gas or coal (in the chapter ‘Nature’s Treasures’ in the Grade 6 Science textbook Curiosity). The electric supply from these sources reaches our homes and factories via wires. For example, at home we plug in various devices to the electrical sockets in the wall. However, to learn about electricity, we will focus on a portable source of electricity that most of us may have used. Let us start with its use in a common device like a torchlight. Caution —?The danger signs on electric poles and other appliances warn people that electricity can be dangerous if not carefully handled. Never ever perform experiments with power supply at your home or school. Even electricity from portable generators can be dangerous. Use only batteries or cells, like those in torchlights, wall clocks, radios, or remotes, for experiments with electricity. 3.1 A Torchlight You might have used a torchlight, also called a torch or a ??ashlight. Activity 3.1: Let us explore ?? Take a torchlight similar to the one shown in Fig. 3.1. ?? Observe it carefully. Do you notice a lamp? And a switch? ?? Slide its switch and observe. Does the torch lamp glow? ?? Now slide the switch back to its original position and observe the torch lamp. You might have noticed that in one position of the switch, the torch lamp glows and in the other position the lamp does not glow. ?? Now, open the torchlight. What do you ??nd inside? Inside the torchlight, you may ??nd two or more electric cells. Why does the torch lamp glow in one position of its switch? Fig. 3.1: A torchlight Chapter 3.indd 24 Chapter 3.indd 24 09-09-2025 11.29.52 AM 09-09-2025 11.29.52 AM Reprint 2026-27 Electricity: Circuits and their Components 25 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit To understand how a torch works, let us ?? rst ?? nd out about its components. 3.2.1 Electric cell Activity 3.2: Let us observe ?? Take an electric cell, turn it around and look at it carefully (Fig. 3.2). Do you notice a positive (+) sign and a negative (–) sign marked on the electric cell? Do you also notice that it has a small protruding metal cap on one side and a ?? at metal disc on the other side? All electric cells have two terminals; one is called positive (+?ve) while the other is negative (–?ve). The metal cap is the positive terminal of the electric cell and the metal disc is the negative terminal. The electric cell is a portable source of electrical energy . 3.2.2 Battery Activity 3.3: Let us experiment ?? Take a torch which uses two cells. Open its cell compartment and take out the cells. ?? Put the cells back in a di?? erent order. Also, try reversing the direction of one cell. Then, slide the switch and check whether the lamp glows in each case. ?? Check the order in which the cells were placed in the torch when the lamp glows. The lamp glows when the cells are placed in the order as shown in Fig. 3.3. Notice how the terminals of the two cells are connected. The positive terminal of one cell is connected to the negative terminal of the next cell. Such a combination of two or more cells is called a battery. (a) (b) Fig. 3.3: A battery made up of (a) two cells (b) four cells Fig. 3.2: An electric cell Positive terminal Negative terminal In a torch, we generally use more than one cell. Are those placed in any particular order? Chapter 3.indd 25 Chapter 3.indd 25 4/3/2025 4:51:26 PM 4/3/2025 4:51:26 PM Reprint 2026-27 Curiosity | Textbook of Science | Grade 7 26 Fig. 3.4: (a) A small incandescent lamp used in a torch (b) its simpli?? ed drawing showing the connection of wires to the terminals However, my torch has a di?? erent kind of lamp. In fact, it cannot be taken out of the torch as it is ?? xed in it. (b) For many devices, we may need more than one cell. So, we connect two or more cells together as shown in Fig. 3.3. Connecting more than one cell provides energy to the circuit for a longer time and/or more energy. FASCINATING FACTS The term battery is also used for a single cell. We use the term battery even for the single cell that powers our mobile phones. 3.2.3 Electric lamp Incandescent Lamp Activity 3.4: Let us observe (a) Glass bulb Thick wire Insulator (support) Insulator Filament Thick wire Metal case (other terminal) Metal tip (one terminal) Metal case Metal case terminal) terminal) For this activity, you will require a torchlight with an incandescent lamp (or light bulb). Many old torchlights still use such lamps. With your teacher’s help, con?? rm that your torchlight uses an incandescent lamp. ?? Take the torch and examine its lamp. What do you see? Do you notice a thin wire ?? xed in the middle of the glass bulb? ?? Now, switch on the torch. Which part of the lamp glows? The thin wire inside the glass bulb of the lamp glows. The glowing thin wire is called the ?? lament of the lamp. ?? Take out the lamp with the help of your teacher and inspect it from all sides. How is the ?? lament ?? xed? The ?? lament is attached to two thicker wires that support it, as shown in Fig. 3.4a. One thick wire connects to the metal case at the lamp’s base, while the other connects to the metal tip at the centre of the base (Fig. 3.4b). These form the two terminals of the lamp, and are ?? xed in a way that they do not touch each other. In such incandescent lamps, the ?? lament gets hot and glows to produce light. Chapter 3.indd 26 Chapter 3.indd 26 4/3/2025 4:51:27 PM 4/3/2025 4:51:27 PM Reprint 2026-27 Page 5 Electricity: Circuits and their Components 3 Nihal and his classmates were excited for their school trip to the Bhakra Nangal Dam. There they would visit the hydroelectric power house where the force of falling water was used to generate electricity. They also looked forward to the free 13 kilometre- train ride from Nangal in Punjab to Bhakra in Himachal Pradesh, along the beautiful Sutlej river and through the Shivalik hills. Prior to the trip, Nihal and his classmates were given a group assignment to prepare a presentation on the uses of electricity. They began by looking around their houses, then their school, followed by their neighbourhood, their city, and ?? nally they searched the internet. To their astonishment, their list kept growing. They decided to organise the uses under di?? erent headings. Entertainment Television, radio, _______________ Communication Mobile phone, Internet, _______________ Others Water pump, crane, computer , _______________ Lighting Homes, o?? ces, streets, markets, factories, _______________ Cooking Electric kettle, mixer grinder, toaster , oven, microwave, _______________ Transportation Train, bus, car, scooter , lift, escalator , _______________ Heating and Cooling Fan, room heater , immersion rod, geyser , refrigerator , air conditioner , _____ Chapter 3.indd 23 Chapter 3.indd 23 4/3/2025 4:51:22 PM 4/3/2025 4:51:22 PM Reprint 2026-27 Curiosity | Textbook of Science | Grade 7 24 Can you help Nihal by adding some more uses to his lists? Also, suggest some other ways of grouping the uses of electricity. We use electricity all the time, so let us learn something more about electricity. You have learnt earlier that electricity is generated in multiple ways?—?by windmills, by using wind energy, by solar panels capturing the Sun’s energy, by falling water and by using natural gas or coal (in the chapter ‘Nature’s Treasures’ in the Grade 6 Science textbook Curiosity). The electric supply from these sources reaches our homes and factories via wires. For example, at home we plug in various devices to the electrical sockets in the wall. However, to learn about electricity, we will focus on a portable source of electricity that most of us may have used. Let us start with its use in a common device like a torchlight. Caution —?The danger signs on electric poles and other appliances warn people that electricity can be dangerous if not carefully handled. Never ever perform experiments with power supply at your home or school. Even electricity from portable generators can be dangerous. Use only batteries or cells, like those in torchlights, wall clocks, radios, or remotes, for experiments with electricity. 3.1 A Torchlight You might have used a torchlight, also called a torch or a ??ashlight. Activity 3.1: Let us explore ?? Take a torchlight similar to the one shown in Fig. 3.1. ?? Observe it carefully. Do you notice a lamp? And a switch? ?? Slide its switch and observe. Does the torch lamp glow? ?? Now slide the switch back to its original position and observe the torch lamp. You might have noticed that in one position of the switch, the torch lamp glows and in the other position the lamp does not glow. ?? Now, open the torchlight. What do you ??nd inside? Inside the torchlight, you may ??nd two or more electric cells. Why does the torch lamp glow in one position of its switch? Fig. 3.1: A torchlight Chapter 3.indd 24 Chapter 3.indd 24 09-09-2025 11.29.52 AM 09-09-2025 11.29.52 AM Reprint 2026-27 Electricity: Circuits and their Components 25 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit 3.2 A Simple Electrical Circuit To understand how a torch works, let us ?? rst ?? nd out about its components. 3.2.1 Electric cell Activity 3.2: Let us observe ?? Take an electric cell, turn it around and look at it carefully (Fig. 3.2). Do you notice a positive (+) sign and a negative (–) sign marked on the electric cell? Do you also notice that it has a small protruding metal cap on one side and a ?? at metal disc on the other side? All electric cells have two terminals; one is called positive (+?ve) while the other is negative (–?ve). The metal cap is the positive terminal of the electric cell and the metal disc is the negative terminal. The electric cell is a portable source of electrical energy . 3.2.2 Battery Activity 3.3: Let us experiment ?? Take a torch which uses two cells. Open its cell compartment and take out the cells. ?? Put the cells back in a di?? erent order. Also, try reversing the direction of one cell. Then, slide the switch and check whether the lamp glows in each case. ?? Check the order in which the cells were placed in the torch when the lamp glows. The lamp glows when the cells are placed in the order as shown in Fig. 3.3. Notice how the terminals of the two cells are connected. The positive terminal of one cell is connected to the negative terminal of the next cell. Such a combination of two or more cells is called a battery. (a) (b) Fig. 3.3: A battery made up of (a) two cells (b) four cells Fig. 3.2: An electric cell Positive terminal Negative terminal In a torch, we generally use more than one cell. Are those placed in any particular order? Chapter 3.indd 25 Chapter 3.indd 25 4/3/2025 4:51:26 PM 4/3/2025 4:51:26 PM Reprint 2026-27 Curiosity | Textbook of Science | Grade 7 26 Fig. 3.4: (a) A small incandescent lamp used in a torch (b) its simpli?? ed drawing showing the connection of wires to the terminals However, my torch has a di?? erent kind of lamp. In fact, it cannot be taken out of the torch as it is ?? xed in it. (b) For many devices, we may need more than one cell. So, we connect two or more cells together as shown in Fig. 3.3. Connecting more than one cell provides energy to the circuit for a longer time and/or more energy. FASCINATING FACTS The term battery is also used for a single cell. We use the term battery even for the single cell that powers our mobile phones. 3.2.3 Electric lamp Incandescent Lamp Activity 3.4: Let us observe (a) Glass bulb Thick wire Insulator (support) Insulator Filament Thick wire Metal case (other terminal) Metal tip (one terminal) Metal case Metal case terminal) terminal) For this activity, you will require a torchlight with an incandescent lamp (or light bulb). Many old torchlights still use such lamps. With your teacher’s help, con?? rm that your torchlight uses an incandescent lamp. ?? Take the torch and examine its lamp. What do you see? Do you notice a thin wire ?? xed in the middle of the glass bulb? ?? Now, switch on the torch. Which part of the lamp glows? The thin wire inside the glass bulb of the lamp glows. The glowing thin wire is called the ?? lament of the lamp. ?? Take out the lamp with the help of your teacher and inspect it from all sides. How is the ?? lament ?? xed? The ?? lament is attached to two thicker wires that support it, as shown in Fig. 3.4a. One thick wire connects to the metal case at the lamp’s base, while the other connects to the metal tip at the centre of the base (Fig. 3.4b). These form the two terminals of the lamp, and are ?? xed in a way that they do not touch each other. In such incandescent lamps, the ?? lament gets hot and glows to produce light. Chapter 3.indd 26 Chapter 3.indd 26 4/3/2025 4:51:27 PM 4/3/2025 4:51:27 PM Reprint 2026-27 Electricity: Circuits and their Components 27 Fig. 3.6: LEDs of different colours + - + + + + - - - - LED Lamp Many torches in use today have a Light Emitting Diode (LED) lamp, instead of an incandescent lamp, as shown in Fig. 3.5. Fig. 3.5: An LED lamp for torch LED lamp Fig. 3.5: An LED lamp for torch Fig. 3.5: An LED lamp for torch Activity 3.5: Let us observe ?? Take an LED of any colour (Fig. 3.6) and observe. Do you see any ?? lament inside it? ?? Notice the length of two wires attached to the LED. Do you ?? nd one of those longer than the other? Unlike incandescent lamps, LEDs do not have ?? laments (Fig. 3.6). They also have two terminals, but one is positive (attached to a longer wire) and the other is negative (the shorter wire). A torch may use one or more LEDs, sometimes of di?? erent shapes, in its lamp. After having learnt about the electric cell, battery, and electric lamps, we are now ready to make the torch lamp glow using an electric cell or battery. 3.2.4 Making an electric lamp glow using an electric cell or battery Activity 3.6: Let us construct ?? Take an electric cell, an incandescent lamp used in a torch, a cell holder , a lamp holder, and four lengths of electric wire. ?? Remove about 1 cm of the plastic covering from both ends of each wire to expose the metal. ?? Attach two wires to the two ends of the cell holder as shown in Fig. 3.7a. Chapter 3.indd 27 Chapter 3.indd 27 4/3/2025 4:51:28 PM 4/3/2025 4:51:28 PM Reprint 2026-27Read More
FAQs on NCERT Textbook: Electricity: Circuits and their Components
| 1. What are the main components of an electric circuit and what does each one do? |  |
Ans. An electric circuit contains four essential components: a power source (battery or cell) that provides energy, conducting wires that allow current flow, a load (bulb or resistor) that uses energy, and a switch that controls the circuit. Each component plays a specific role in completing the circuit path and allowing electricity to flow safely and effectively.
| 2. Why does my bulb not light up even when the battery is connected in a circuit? | |
Ans. A bulb fails to light when the circuit is incomplete or broken. Common reasons include loose wire connections, a faulty switch in the open position, a dead battery with no voltage, or a broken filament inside the bulb itself. Students should check all connections and ensure the switch is closed to allow current to flow continuously through the circuit.
| 3. What's the difference between series circuits and parallel circuits in Class 7 science? | |
Ans. In a series circuit, components connect in a single loop, so current flows through each part sequentially-if one breaks, all stop working. In a parallel circuit, components connect on separate branches, allowing current to take multiple paths. If one branch fails, others continue functioning, making parallel circuits more practical for home electrical systems.
| 4. How does a switch actually control the flow of electricity through a circuit? | |
Ans. A switch interrupts or completes the circuit path by opening and closing a gap in the conducting wire. When closed, it allows electrons to flow continuously from the battery through all components. When open, it breaks the path, stopping current flow instantly. This simple mechanism controls whether devices receive power or remain off.
| 5. What materials can conduct electricity and why should I know this for my CBSE exams? | |
Ans. Conductors like copper, aluminum, and silver allow electricity to flow easily because they have free electrons that move readily. Insulators like rubber, plastic, and wood resist current flow, protecting users from shocks. Understanding conductor and insulator properties is crucial for circuit safety and appears frequently in CBSE Class 7 electricity questions about material selection in real-world applications.
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