Extra Questions for Chapter 3 Electricity: Circuits and their Components Class 7 Science Curiosity
Class 7 Science Electricity: Circuits and their Components Extra Questions
Very Short Answer Questions
Question 1. Draw the symbol for an electric bulb in an electric circuit.
Answer
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| Symbol of an Electric bulb |
Question 2. A Longer line in the symbol for a cell represents its ____ terminal.
Answer
positive
Question 3. What is an electric circuit?
Answer
An Electric Circuit is a closed path in which electric current flows.
Question 4. What type of electricity is used in homes and industries?
Answer
Alternating Current (AC).
Question 5. What is a torchlight?
Answer
A torchlight is a portable device that produces light, commonly used to see in the dark.
Question 6. What happens if the filament in an incandescent lamp breaks?
Answer
The lamp stops glowing because the circuit is broken.
Question 7. How does a torchlight produce light?
Answer
By passing current through a lamp powered by electric cells.
Question 8. Why do we use copper wires in electrical circuits?
Answer
Copper is a good conductor of electricity, which allows the current to flow easily through the wires.
Question 9. What happens when the current is switched ‘on’ in a room heater?
Answer
It becomes red hot and gives out heat.
Question 10. What is filament?
In the bulb there is a thin wire, called the filament, which glows when an electric current passes through it.
Question 11. 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.
Question 12. What is a cell holder?
Answer
A compartment that holds two or more cells together to form a battery is called a cell holder.
Question 13. Would any of the bulbs glow when the switch is in the ‘OFF’ position in a circuit?
Answer
No, the bulb will not glow when the switch is "OFF" because there is no closed circuit for current to flow.
Question 14. What is the purpose of using insulators in circuits?
Answer
To prevent electric shocks and ensure safety.
Short Answer Questions
Question 1. Name any two effects of electric current.
Answer
The two effects of electric current are:
- Heating effect of electric current
- Magnetic effect of the electric current
Question 2. What are the uses of heating effect of electric current?
Answer
The heating effect of electric current is utilised in various electrical appliances, including:
- Immersion heaters
- Hotplates
- Irons
- Geysers
- Electric kettles
- Hair dryers
Question 3. What is electric current and its unit?
Answer
Electric current is the flow of electrons through a conductor, such as a wire. It is measured in amperes.
Question 4. Explain the symbol of electric cell.
Answer
In the symbol of an electric cell, the representation consists of:
- The longer line indicates the positive terminal.
- The thicker, shorter line represents the negative terminal.
Question 5. Write some uses of battery.
Answer
Usage of Battery:
- Torches for lighting
- Transistors for amplifying signals
- Toys for operation
- TV remote controls for convenience
Question 6. Why a fused bulb does not glow?
Answer
A fused bulb does not glow due to a break in its filament. This break interrupts the flow of current between the bulb's terminals. As a result,
- The circuit becomes incomplete.
- No current passes through the filament.
- Thus, the bulb remains unlit.
Question 7. Sometimes the cells are placed side by side. Then how are the terminals of the cells connected?
Answer
Cells are typically connected using:
- A thick wire or a metal strip that links the positive terminal of one cell to the negative terminal of the next.
- This connection allows the cells to work together as a battery.
Question 8. What is a switch, and how does it control an electric circuit?
Answer
A switch is a device that either completes (ON) or breaks (OFF) a circuit. When the switch is ON, the circuit is closed, and current flows, making the device work. When OFF, the circuit opens, stopping the current. Switches can be placed anywhere in the circuit and are essential for safe control of electricity.
Question 9. Explain the importance of circuit diagrams and list three symbols used.
Answer
Circuit diagrams help represent electric circuits using symbols, making them easy to understand and communicate. They are important in designing, testing, and explaining circuits. Common symbols include:
Question 10. Describe the difference between an incandescent lamp and an LED.
Answer
An incandescent lamp has a filament that glows when current passes through it and can work in either direction of connection. An LED does not have a filament; it only glows when connected correctly, with the longer wire to the positive terminal and the shorter wire to the negative. LEDs are energy-efficient and long-lasting.
Question 11. What are conductors and insulators? Give examples and their uses.
Answer
Conductors are materials that allow electricity to pass easily, like copper and aluminium, used in wires and plugs. Insulators block current and include rubber, plastic, and glass. They are used to cover wires, make switches, and ensure electrical safety by preventing shocks.
Question 12. Define electric circuit.
Answer
A closed path formed by connecting electrical components allows electric current to flow. This arrangement is known as an electric circuit.
Question 13. What is a battery?
Answer
A combination of two or more cells connected together is called a battery. It is formed by connecting the positive terminal of one cell to the negative terminal of another.
Question 14. What is a circuit diagram?
Answer
A circuit diagram is a simplified representation of an electrical circuit using symbols to depict various components.
Question 15. What direction does current flow in a circuit?
Answer
From the positive terminal of the cell to the negative terminal.
Question 16. 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.
Question 17. 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.
Question 18. 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.
Question 19. 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.
Question 20. 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.
Question 21. What is an incandescent lamp?
Answer
An incandescent lamp has a filament inside that glows when electric current passes through it, producing light.
Question 22. What is a circuit diagram?
Answer
A circuit diagram is a drawing that uses standard symbols to represent the components of an electrical circuit.
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| Circuit Diagram |
Question 23. 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.
Question 24. What is an electric circuit, and why is it important?
Answer
An electric circuit is a closed path that allows electric current to flow from a power source through a device and back. It is important because it enables devices like lamps to work by providing a complete path for current flow.
Question 25. Explain the difference between a conductor and an insulator.
Answer
Conductors are materials, like metals (e.g., copper), that allow electric current to flow easily due to their ability to conduct electricity. Insulators, such as plastic, rubber, or glass, do not allow electric current to pass through, preventing the flow of electricity. Conductors are used in wires, while insulators are used to cover wires to ensure safety.
Question 26. How does an LED lamp differ from an incandescent lamp in a torchlight?
Answer
An LED lamp has no filament, glows only when correctly connected (positive to positive terminal), and is more efficient, while an incandescent lamp has a filament that glows regardless of terminal connections but is less efficient.
Question 27. What is the purpose of a switch in an electrical circuit?
Answer
A switch completes or breaks an electrical circuit to control the flow of current.
For example, in a torchlight, sliding the switch to the “ON” position completes the circuit, making the lamp glow, while moving it to “OFF” breaks the circuit, turning the lamp off.
Question 28. Why is it important to connect cells in a specific order in a battery?
Answer
Cells in a battery must be connected with the positive terminal of one cell to the negative terminal of the next to ensure proper current flow. This arrangement forms a complete circuit, providing sufficient energy to power a device. Incorrect connections may prevent the device, like a torch, from functioning.
Question 29. How does an incandescent lamp produce light?
Answer
An incandescent lamp produces light when electric current passes through its filament, a thin wire inside the bulb. The filament gets hot and glows, emitting light. The filament is supported by two thicker wires connected to the lamp’s terminals.
Question 30. What is an electrical circuit, and why is it necessary for a lamp to glow?
Answer
An electrical circuit is a complete path that allows electric current to flow from the positive to the negative terminal of a power source, like a cell. It is necessary for a lamp to glow because the current must pass through the lamp’s filament or LED to produce light, which only happens when the circuit is complete.
Question 31. Why are electrical wires covered with plastic or rubber?
Answer
Electrical wires are covered with plastic or rubber because these materials are insulators, preventing unwanted flow of electric current. This covering protects users from electric shocks and prevents short circuits by ensuring current flows only through the conductive metal inside the wire.
Question 32. Define conductors and insulators, and give one example of each.
Answer
Conductors allow electric current to flow easily. Example: copper.
Insulators block current flow. Example: plastic.
Question 33. What is the role of a cell holder in a circuit?
Answer
A cell holder securely places the electric cell in a circuit, ensuring proper connection of the cell’s terminals to wires for current flow.
Question 34. Why is a circuit diagram useful?
Answer
A circuit diagram uses standard symbols to represent components, making it easy to understand, draw, and build electrical circuits accurately.
Question 35. Draw a neat circuit diagram of a torchlight, labelling the electric cell, lamp, switch, and wires.
Answer
Long Answer Questions
Question 1. What is an electric circuit and how it works?
An electric circuit is a closed path that allows electricity to flow between the two terminals of an electric cell. Key points include:
- The circuit must be closed for current to flow.
- A bulb will only glow when the current is flowing through the circuit.
- If the circuit is open (e.g., when a switch is off), no current flows.
In the bulb, a thin wire called the filament glows when electric current passes through it. If the filament is broken, the circuit becomes incomplete, and the bulb will not glow.
Question 2. Explain how a battery is formed and its advantage over a single cell.
Answer
- A battery is formed by connecting two or more electric cells in a specific order, with the positive terminal of one cell connected to the negative terminal of the next.
- This arrangement ensures a continuous flow of current.
- The advantage of a battery over a single cell is that it provides more electrical energy, allowing devices to operate for a longer time or with greater power.
- For example, a torch with a battery of two cells can produce brighter light or function longer than one with a single cell, as the combined cells deliver more energy to the circuit.
Question 3. Explain how an electric cell works in providing energy to a device.
Answer
An electric cell is a source of electrical energy.
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| Electric Cell |
- It has two terminals: a positive (+) terminal and a negative (-) terminal. 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.
Question 4. 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.
Question 5. What are the roles of conductors and insulators in electrical circuits?
Answer
In an electrical circuit, conductors and insulators play important roles:
- Conductors are materials that allow electricity to flow through them easily. Metals like copper, silver, and aluminium 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.
Question 6. Describe the differences between conductors and insulators, and their uses in electrical circuits, with examples.
Answer
Conductors and insulators differ in their ability to handle electric current:
- Conductors: Materials like copper, silver, and aluminium allow current to flow easily due to their structure. They are used in wires (e.g., copper wires in circuits), switches, and plugs to carry current efficiently. Copper is preferred for its conductivity, cost, and availability.
- Insulators: Materials like plastic, rubber, and glass block current flow, preventing unwanted electrical movement. They are used to cover wires (e.g., plastic insulation), make plug tops, and switches to protect users from shocks. Rubber gloves are another example used for safety.
In circuits, conductors ensure current reaches devices like lamps, while insulators prevent shocks and short circuits. For example, in a torchlight, copper wires (conductors) connect the cell to the lamp, and a plastic body (insulator) encases the circuit, ensuring safe operation, highlighting their complementary roles in electrical safety and functionality.
Question 7. 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.
Question 8. 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.
Question 9. How do electric cells or batteries make the use of electrical devices more convenient, and what are some examples of their different forms and uses?
Answer
- Electric cells or batteries are compact portable sources of electrical energy that make the use of some electrical devices more convenient.
- These cells and batteries come in various shapes and sizes for different purposes.
- For Example in cylindrical batteries for torchlights, clocks, remotes, toys; button cells for watches, hearing aids; rechargeable batteries for mobile phones, laptops, and electric vehicles.
Question 10. Explain how a torchlight works, describing the role of its main components.
Answer
A torchlight produces light using a simple electrical circuit with key components:
- Electric Cells: Provide electrical energy through a chemical reaction, with a positive (+) and negative (-) terminal.
- Lamp: An incandescent lamp or LED that glows when current flows through it. Incandescent lamps have a filament that heats up, while LEDs require correct terminal alignment.
- Switch: Controls current flow by closing (ON) or opening (OFF) the circuit. When ON, it connects the cells to the lamp, allowing current to flow; when OFF, it breaks the circuit, stopping the light.
- Wires: Connect the components, allowing current to flow from the negative terminal of the cell, through the lamp, and back to the positive terminal.
When the switch is ON, the circuit is complete, and current flows from the cells through the lamp, making it glow. This portable design makes torchlights useful for seeing in the dark, as explored by Nihal’s class.
Question 11. Discuss the importance of circuit diagrams and the role of switches in controlling electrical circuits, with examples.
Answer
Circuit diagrams and switches are crucial in electrical circuits:
Circuit Diagrams:
- These are drawings using standard symbols (set by organizations like IEC) to represent components like cells, lamps, and wires.
- They simplify complex circuits, making them easy to understand, design, and build globally.
- For example, a diagram for a torchlight shows a cell (long/short lines), lamp (circle with loop), and switch (break in line), guiding Nihal’s class to visualize how current flows.
Switches:
- A switch controls current by closing (ON) or opening (OFF) the circuit.
- When ON, it completes the path, allowing current to flow (e.g., turning on a torchlight’s lamp).
- When OFF, it breaks the path, stopping current (e.g., turning off the lamp).
- Switches can be placed anywhere in the circuit, as seen in home light switches or torch sliders.
Together, circuit diagrams help plan circuits accurately, while switches provide practical control, ensuring devices work only when needed, enhancing safety and efficiency in applications like Nihal’s torchlight or household lighting.