Topic outline

    • Electricity and Circuits

      Q24. Where dry cells are used?

      Ans. It is the most commonly used cell and used in calculators, torches, toys, flashlights, portable radios, cameras, hearing aids etc.


      Q25. What are terminals?

      Ans. The electrical contacts of an electric cell or a battery or any other electronic device are known as terminals.


      Q26. What is dry cell?

      Ans. Dry cell is an electric cell in which the chemicals are made into a paste so that they cannot easily spill from their container.


      Q27. What is solar cell?

      Ans. A solar cell is an electrical device that converts the solar energy directly into electricity.

      Q28. What is an electric cell?

      Ans. An electric cell is a device that produces electricity from the chemicals stored inside it.


      Q29. What is the difference between a cell and a battery?

      Ans. A cell is a single unit which converts chemical energy into electrical energy whereas a battery is a collection of cells.


      Q30. Name few devices where electric cell are used.

      Ans. Electric cell are used in torch, alarm clocks, wristwatches, transistor radios, cameras and many other devices.


      Q31. Why are rubber and plastics used for covering electrical wires?

      Ans. Rubber and plastics are used for covering electrical wires because they are insulators and do not allow electric current to pass when we touch them.


      Q32. What is an electric circuit diagram?

      Ans. An electric circuit diagram indicates the arrangement of different circuit elements with their conventional symbols.

      Q33. Where insulators are used?

      Ans. Electrical insulators may be used for circuit boards, switches, coating on electric wire and cable, handles of screw driver and tester etc.


      Q34. Air is an insulator. Prove with help of an activity.

      Ans. In an electric circuit keep the terminals unconnected. Since the bulb does not glow when there is only air in the gap, it means that air is also an insulator.


      Q35. What are the different sources of electric current?

      Ans. The different sources of electric current are:

      i.             Primary cells

      ii.            Secondary cells or accumulators

      iii.          Power house


      Q36. What do you understand by an electric circuit?

      Ans. The electric circuit provides a closed path for electricity to pass between the two terminals of the electric cell. The bulb glows only when current flows through the circuit.


      Q37. Electrician uses rubber gloves while repairing electric switches. Give reason.

      Ans. Human body is a good conductor of electricity and may get shock. To prevent themselves from electric shock, electrician wears rubber gloves while repairing electric switches.

      Q38. What does an electric circuit consist of?

      Ans. An electric circuit mainly consists of electric devices (such as computer, light bulb), switching devices, source of electricity (such as battery), etc. that are connected by conducting wires.


      Q39. If an electrician uses a conduction tester on an object, the bulb of the tester glows. Is the object a conductor or insulator?

      Ans. The bulb of tester would glow only if the object conducts electricity. Since, bulb glows when tester touches the object, object must be a conductor.


      Q40. If we use two strip of aluminum foil in place of connecting wire to glow a torch bulb using a cell, will bulb glow? Explain, how?

      Ans. Electricity can flow through conductors but not insulators. In the following activity, we used aluminum foil which is a conductor, hence bulb will glow.


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