Electricity: Circuits and Their Components – Very Short Answer Type Questions

Q1. What is electricity?

Ans. Electricity is a form of energy produced by the flow of electric charges (current) through a conductor.

Q2. What is an electric circuit?

Ans. An electric circuit is a closed path along which electric current can flow from one terminal of a cell to the other.

Q3. What condition is necessary for current to flow in a circuit?

Ans. The circuit must be closed (complete) without any break in the path.

Q4. What is a closed circuit?

Ans. A closed circuit is one in which the path of current is complete and the current can flow.

Q5. What is an open circuit?

Ans. An open circuit is one in which the path of current is broken, so electric current cannot flow.

Q6. In which direction do we show conventional current in a circuit?

Ans. Conventional current is shown flowing from the positive terminal of the cell to the negative terminal.

Q7. Name any two devices that work on electricity in your home.

Ans. Examples: Electric bulb, fan, television, mixer, refrigerator (any two).

Q8. Why does a bulb not glow in an open circuit?

Ans. Because the path for current is broken, so no current flows through the bulb.

Q9. What do we call materials through which current can easily flow?

Ans. They are called conductors.

Q10. What do we call materials through which current cannot flow?

Ans. They are called insulators.

Q11. What is an electric cell?

Ans. An electric cell is a device that converts chemical energy into electrical energy.

Q12. Name the two terminals of a cell.

Ans. Positive terminal and negative terminal.

Q13. How is the positive terminal of a cell usually shown?

Ans. It is usually shown as a raised metal cap and marked with a plus (+) sign.

Q14. How is the negative terminal of a cell usually shown?

Ans. It is usually the flat metal base and is marked with a minus (–) sign.

Q15. What is a battery?

Ans. A battery is a combination of two or more cells connected together.

Q16. How are cells connected in a battery?

Ans. The positive terminal of one cell is connected to the negative terminal of the next cell.

Q17. Why do we sometimes use a battery instead of a single cell?

Ans. A battery provides more electrical energy and can run devices for longer or make them work better.

Q18. Name any two devices that commonly use batteries.

Ans. Torch, TV remote, toys, wall clock, mobile phone (any two).

Q19. In a circuit diagram, how is a cell represented?

Ans. By two parallel lines – the longer line for the positive terminal and the shorter line for the negative terminal.

Q20. What happens to a cell after long use?

Ans. The chemicals inside get used up and the cell is said to be “discharged” or “dead”.

Q21. What is an electric bulb?

Ans. An electric bulb is a device that produces light when electric current passes through its filament.

Q22. What is the filament of a bulb?

Ans. The filament is a very thin wire inside the bulb that gets heated and glows when current flows through it.

Q23. Name the material commonly used for bulb filaments.

Ans. Tungsten is commonly used for bulb filaments.

Q24. Why is the filament of a bulb enclosed in a glass cover?

Ans. To protect the filament from air so that it does not burn out quickly.

Q25. What is a fused bulb?

Ans. A fused bulb is one whose filament is broken, so it does not glow even if the circuit is complete.

Q26. Will a fused bulb glow in a closed circuit? Give reason.

Ans. No, because the filament is broken and current cannot pass through the bulb.

Q27. Why does a bulb glow when connected correctly in a closed circuit?

Ans. Because current flows through the filament, heating it so that it glows.

Q28. Why should we not touch a glowing bulb?

Ans. Because the filament and the bulb become very hot and can burn our skin.

Q29. Define a conductor.

Ans. A conductor is a material that allows electric current to pass through it easily.

Q30. Give two examples of conductors.

Ans. Copper, aluminium, iron (any two metals).

Q31. Define an insulator.

Ans. An insulator is a material that does not allow electric current to pass through it easily.

Q32. Give two examples of insulators.

Ans. Rubber, plastic, glass, dry wood (any two).

Q33. Why are electric wires usually covered with plastic?

Ans. Because plastic is an insulator and protects us from electric shocks.

Q34. Is human body a conductor or an insulator?

Ans. The human body is a conductor of electricity.

Q35. Is distilled water a good conductor of electricity?

Ans. No, pure distilled water is a poor conductor of electricity.

Q36. How does adding salt to water change its conductivity?

Ans. Adding salt makes water a better conductor of electricity.

Q37. What is a switch (or key)?

Ans. A switch is a device used to open or close an electric circuit.

Q38. What happens to the circuit when the switch is ON?

Ans. The circuit becomes closed and current flows.

Q39. What happens to the circuit when the switch is OFF?

Ans. The circuit becomes open and current does not flow.

Q40. What is a circuit diagram?

Ans. A circuit diagram is a simple drawing of a circuit using standard symbols for different components.

Q41. Why do we use symbols in circuit diagrams?

Ans. Symbols make circuit diagrams easy to draw, read and understand.

Q42. In a circuit diagram, how is a connecting wire shown?

Ans. A connecting wire is shown by a straight line.

Q43. In which direction is current shown in a circuit diagram?

Ans. From the positive terminal of the battery to the negative terminal.

Q44. What is the heating effect of electric current?

Ans. When current flows through a conductor, it produces heat; this is called the heating effect of electric current.

Q45. Name two devices that work on the heating effect of electric current.

Ans. Electric iron, electric heater, electric kettle (any two).

Q46. What is an electric fuse?

Ans. A fuse is a safety device with a thin wire that melts and breaks the circuit if too much current flows.

Q47. Why is a fuse connected in series in a circuit?

Ans. So that when the fuse wire melts, it can break the entire circuit and stop the current.

Q48. Name the modern device used in homes instead of traditional fuses.

Ans. MCB – Miniature Circuit Breaker.

Q49. Why should we not touch electrical switches with wet hands?

Ans. Because water conducts electricity and can cause an electric shock.

Q50. Why should we not overload a plug point with too many appliances?

Ans. Overloading can cause excessive current, leading to heating of wires, fire or damage to appliances.