Electricity: Circuits and Their Components – Short Answer Type Questions

Q1. What is electricity? State one use of electricity in our daily life.

Ans. Electricity is a form of energy produced by the flow of electric charges (current) through a conductor. It is used for many purposes, for example, to light bulbs and tube lights in our homes.

Q2. Define an electric circuit.

Ans. An electric circuit is a closed and continuous path along which electric current flows. It usually consists of a cell or battery, connecting wires, a switch and an appliance such as a bulb.

Q3. Differentiate between an open circuit and a closed circuit.

Ans. In a closed circuit, the path of current is complete and current can flow, so the bulb glows. In an open circuit, the path is broken (for example, a switch is off or a wire is disconnected) and current cannot flow, so the bulb does not glow.

Q4. Why does a bulb not glow if the connecting wires are not properly attached to its terminals?

Ans. If the wires are not properly attached, the circuit is incomplete or loose. Since the circuit is not truly closed, electric current cannot pass through the bulb’s filament and the bulb will not glow.

Q5. What is meant by “conventional direction of current” in a circuit?

Ans. Conventional direction of current is the direction from the positive terminal of a cell or battery to the negative terminal through the external circuit. We follow this direction while drawing circuit diagrams.

Q6. Why is it dangerous to touch a live electric wire with bare hands?

Ans. Our body is a good conductor of electricity. If we touch a live wire, a large current can pass through our body to the earth and give a severe electric shock, which can be fatal.

Q7. State two conditions required for the bulb to glow in a simple electric circuit.

Ans. (i) The circuit must be closed from one terminal of the cell back to the other.
(ii) The bulb must be in working condition, i.e., its filament should not be broken (not fused).

Q8. Why does the bulb stop glowing when the switch in a circuit is turned off?

Ans. Turning the switch off opens the circuit and creates a gap in the path of current. As the closed path for current is broken, no current flows through the bulb’s filament, so the bulb stops glowing.

Q9. Mention any two uses of electricity in modern life.

Ans. (i) Electricity is used for lighting homes, streets and offices using bulbs and tube lights.
(ii) It is used to run electrical appliances like fans, televisions, refrigerators, computers and many more devices.

Q10. Why is it important to understand simple electric circuits at school level?

Ans. Understanding simple circuits helps us know how electrical devices in our surroundings work. It also develops scientific thinking, makes us aware of safety rules and prepares us for further studies in science and technology.

Q11. What is an electric cell? How does it provide energy?

Ans. An electric cell is a small device that converts chemical energy stored inside it into electrical energy. A chemical reaction inside the cell produces a potential difference between its terminals, which pushes current through a circuit.

Q12. Describe the appearance of the two terminals of a dry cell.

Ans. In a dry cell, the positive terminal is the small, raised metal cap on one end and is marked with a plus (+) sign. The negative terminal is the flat metal base on the opposite end, marked with a minus (–) sign.

Q13. Why should the two terminals of a cell never be connected directly with a wire?

Ans. Connecting the terminals directly can cause a short circuit. Very large current will flow, which may heat the cell and wire, damage the cell quickly and can be dangerous.

Q14. What is a battery? Give one example of its use.

Ans. A battery is a combination of two or more cells connected together. For example, a torch usually uses two or three cells arranged in a row to form a battery, which provides enough energy to light the bulb.

Q15. How are cells connected to make a battery in a torch?

Ans. The cells are arranged so that the positive terminal of one cell touches the negative terminal of the next cell. The free negative terminal of the first cell and the free positive terminal of the last cell act as the battery terminals.

Q16. Why is a battery more useful than a single cell for some devices?

Ans. Some devices require more energy or a higher potential difference than a single cell can provide. A battery formed by several cells can supply more energy and operate such devices more effectively and for a longer time.

Q17. What do we mean when we say a cell is “discharged” or “dead”?

Ans. A discharged or dead cell is one in which most of the chemical energy has been used up. It can no longer provide enough potential difference to push current, so devices connected to it do not work properly.

Q18. Drawbacks of using too many cells in a battery are sometimes mentioned. State one such drawback.

Ans. Using many cells increases the size and weight of the battery, making the device bulky and hard to handle. Also, if one cell goes weak, the performance of the whole battery may reduce.

Q19. Explain briefly how an electric bulb produces light.

Ans. When electric current passes through the thin filament of the bulb, the filament gets heated to a high temperature. At this high temperature it starts glowing and gives out light, along with some heat.

Q20. What is meant by the term “filament” of a bulb?

Ans. The filament is the thin wire inside the glass bulb that actually glows when current flows through it. It offers resistance to the current and gets heated up, which makes it emit light.

Q21. Why is tungsten used as filament material in bulbs?

Ans. Tungsten has a very high melting point and can become very hot without melting. This allows it to glow brightly for a long time without getting damaged, so it is used as filament material.

Q22. What is a fused bulb? How can you test if a bulb is fused?

Ans. A fused bulb is a bulb whose filament has broken. You can test it by connecting it in a proper circuit with a working cell; if the circuit is closed but the bulb does not glow while another bulb does, the bulb is fused.

Q23. Can a fused bulb complete a circuit? Give reason.

Ans. No, a fused bulb cannot complete a circuit because its filament is broken. The break in filament behaves like an open circuit, so electric current cannot pass through the bulb.

Q24. Why does a bulb often become hot when it is glowing?

Ans. When current passes through the filament, it faces resistance and electrical energy is converted to heat. This heating effect raises the temperature of the filament and bulb, making it hot when glowing.

Q25. Why is the filament of a bulb enclosed in a glass cover filled with special gas or vacuum?

Ans. If the red-hot filament were in contact with air, it would burn out quickly. The glass cover and special gas or vacuum protect the filament from air and increase the life of the bulb.

Q26. A student connects a bulb to a cell with wires, but the bulb does not glow. List any two possible reasons.

Ans. (i) The bulb may be fused or damaged.
(ii) The circuit may not be closed due to loose connections, wrong connections of terminals or a broken wire.

Q27. Define a conductor with one example.

Ans. A conductor is a material through which electric current can pass easily. Metals such as copper are good conductors and are used for making electric wires.

Q28. Define an insulator with one example.

Ans. An insulator is a material that does not allow electric current to pass through it easily. Rubber is an insulator and is used to cover wires and handles of tools.

Q29. Why are cooking pans often made of metal but provided with plastic or wooden handles?

Ans. Metals conduct heat and allow pans to heat quickly, but they also become hot. Plastic or wood handles do not conduct heat or electricity easily, so they protect our hands from burns and shocks.

Q30. How can you experimentally show that a metal wire is a conductor?

Ans. Connect a cell, a bulb and the metal wire in a circuit. If the bulb glows when the metal wire is used, it shows that current is passing through the wire and hence it is a conductor.

Q31. Why is it unsafe to touch electrical appliances with wet hands?

Ans. Water contains dissolved salts and becomes a conductor of electricity. Wet hands allow current to pass through the body more easily, increasing the risk of electric shock when touching appliances.

Q32. Distilled water is a poor conductor, but tap water conducts electricity. Why?

Ans. Distilled water is almost pure and contains no salts, so it does not conduct electricity well. Tap water has dissolved salts and impurities which provide ions, so it can conduct electricity.

Q33. Give one reason why birds do not get an electric shock when they sit on a naked high-voltage wire.

Ans. The bird’s body and the wire are at almost the same electric potential, and the bird is not touching the ground or another wire. So there is no potential difference across its body and almost no current passes through it.

Q34. Why are screwdrivers and pliers used by electricians provided with plastic covers on their handles?

Ans. Plastic is an insulator, so plastic covers prevent electric current from passing through the handles into the electrician’s body. This protects the electrician from electric shocks while working.

Q35. What is an electric switch? What is its main function in a circuit?

Ans. An electric switch is a device used to open or close an electric circuit. Its main function is to control the flow of current, allowing us to switch appliances on or off safely and easily.

Q36. Why is it better to use a switch instead of connecting and disconnecting wires by hand?

Ans. Using a switch is safer, quicker and more convenient. It avoids loose connections and direct contact with wires, reducing the risk of electric shock and damage to the circuit.

Q37. What is a circuit diagram? Why is it useful?

Ans. A circuit diagram is a simplified drawing of an electric circuit using standard symbols for components. It is useful because it is neat, easy to understand, and helps in planning, analysing and explaining electrical connections clearly.

Q38. Name the standard symbol used to represent (i) a cell and (ii) a switch in a circuit diagram.

Ans. (i) A cell is represented by two parallel lines, a longer one for the positive terminal and a shorter one for the negative terminal. (ii) A switch is shown as a small break in the line with a movable part that either connects or disconnects the line.

Q39. How is a battery represented in a circuit diagram?

Ans. A battery is shown as a series of cell symbols placed side by side. The long and short lines alternate, representing the positive and negative terminals of each cell connected together.

Q40. What will happen to the circuit if the switch is mistakenly connected in parallel with the bulb instead of in series?

Ans. If the switch is in parallel with the bulb, closing it will provide an easier path for current without passing through the bulb. The circuit may complete but the bulb will not glow because most of the current will bypass it.

Q41. In a circuit diagram, why do we draw wires as straight lines and not as curved shapes matching real wires?

Ans. Straight lines make the diagram neat and easier to read. The actual shape of the wire in the device does not matter for understanding the connections; only which components are joined is important.

Q42. How can you show the direction of current in a circuit diagram and why is this important?

Ans. We draw arrows along the wires from the positive terminal of the cell to the negative terminal. Showing direction is important for understanding how current flows and for explaining the working of components correctly.

Q43. Explain the heating effect of electric current with one example.

Ans. When electric current passes through a conductor, some electrical energy changes into heat energy. For example, in an electric iron, current heats up a metal coil inside, and this heat is used to press clothes.

Q44. What is an electric fuse and how does it protect the circuit?

Ans. An electric fuse is a small safety device made of a thin wire that melts when too much current flows. When it melts, it breaks the circuit and stops the flow of current, thus preventing damage to wires and appliances and reducing fire risk.

Q45. Why should the fuse wire have a low melting point?

Ans. The fuse wire must melt quickly when the current becomes too high. A low melting point ensures that it breaks the circuit before the rest of the wiring or appliances become very hot and get damaged.

Q46. State any three safety rules you should follow while using electricity at home.

Ans. (i) Never touch switches, plugs or wires with wet hands.
(ii) Do not insert fingers or metal objects into plug points.
(iii) Do not overload a socket with many gadgets and always call an electrician for major repairs.

Q47. What is a series connection? What is its disadvantage in household wiring?

Ans. In a series connection, components are connected one after another in a single path. Its disadvantage is that if one component (like a bulb) fails or is removed, the entire circuit breaks and all devices stop working, which is not suitable for houses.

Q48. What is a parallel connection and why is it preferred in home wiring?

Ans. In a parallel connection, components are connected across the same two points in separate branches. It is preferred at home because each appliance gets the same voltage and can work independently; if one fails, others still work.

Q49. A student wants to connect two bulbs so that if one bulb fuses, the other still glows. Should the bulbs be connected in series or in parallel? Explain.

Ans. The bulbs should be connected in parallel. In a parallel circuit, each bulb has its own branch connected to the cell. If one bulb fuses, current can still flow through the other branch, so the other bulb keeps glowing.

Q50. Why should we never try to repair high-voltage electrical lines or appliances ourselves?

Ans. High-voltage lines and appliances carry large currents that can cause severe shocks or even death. Repairing them needs special training, tools and safety equipment, so only qualified electricians should handle them.