NCERT Class 6 Science Electricity and Circuits

Electricity and Circuits

We use electricity for many purposes to make our tasks easier. For example, we use electricity to operate pumps that lift water from wells or from ground level to the roof top tank. What are other purposes for which  you use electricity? List some of them in your notebook. Does your list include the use of electricity for lighting? Electricity makes it possible to light our homes, roads, offices, markets and factories even after sunset. This helps us to continue working at night. A power stationprovides us with electricity. However, the supply of electricity may fail or it may not be available at some places. In such situations, a torch is sometimes used for providing light. A torch has a bulb that lights up when it is switched on. Where does the torch get electricity from?

12.1. ELECTRIC CELL 

Electricity to the bulb in a torch is provided by the electric cell. Electric cells are also used in alarm clocks, wristwatches, transistor radios, cameras  and many other devices. Have you ever carefully looked at an electric cell? You might have noticed that it has a small metal cap on one side and a metal disc on the other side (Fig. 12.1). Did you notice a positive (+) sign and a negative (–) sign marked on the electric cell? The Fig.12.1 An Electric Cell metal cap is the positive terminal of the electric cell. The metal disc is the negative terminal. All electric cells have two terminals; a positive terminal and a negative terminal.

An electric cell produces electricity from the chemicals stored inside it. When the chemicals in the electric cell are used up, the electric cell stops way that they do not touch each other. The electric bulbs used at home also have a similar design. Thus, both the electric cell and the bulb have two terminals each. Why do they have these two terminals?

12.2. A BULB CONNECTED TO AN ELECTRIC CELL

Let us try to make an electric bulb light up using an electric cell. How do we do that?

Activity 1

Take four lengths of electric wire with differently coloured plastic coverings. Remove a little of the plastic covering from each length of wire at the ends. This would expose the metal wires at the ends of each length. Fix the exposed parts of the wires to the cell and the bulb as shown in Fig 12.3 and Fig. 12.4. Write 'Yes' or 'No' for each arrangement in your notebook. Now, carefully look at the arrangements in which the bulb glows. Compare these with those in which the bulb does not glow. Can you find the reason for the difference? Keep the tip of your pencil on the wire near one terminal of the electric cell for the arrangment in Fig. 12.5 (a). Move the pencil along the wire all the way to the bulb. Now, from the other terminal of the bulb, move along the other wire connected to the cell. Repeat this exercise for all the other arrangements in Fig. 12.5. Did the bulb glow for the arrangements in which you could not move the pencil from one terminal to the other?

Exercises 

1. Fill in the blanks :

(a) A device that is used to break an electric circuit is called _______________.

(b) An electric cell has _______________ terminals.

2. Mark 'True' or 'False' for following statements:

(a) Electric current can flow through metals.

(b) Instead of metal wires, a jute string can be used to make a circuit.

(c) Electric current can pass through a sheet of thermo Col.

3. Explain why the bulb would not glow in the arrangement shown in Fig. 12.13.

4. Complete the drawing shown in Fig 12.14 to indicate where the free ends of the two wires should be joined to make the bulb glow.

5. What is the purpose of using an electric switch? Name some electrical gadgets that have switches built into them.

6. Would the bulb glow after completing the circuit shown in Fig. 12.14 if instead of safety pin we use an eraser?

7. Would the bulb glow in the circuit shown in Fig. 12.15?

8. Using the "conduction tester" on an object it was found that the bulb begins to glow. Is that object a conductor or an insulator? Explain.

9. Why should an electrician use rubber gloves while repairing an electric switch at your home? Explain.

10. The handles of the tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. Can you explain why?

Please refer to attached file for NCERT Class 6 Science Electricity and Circuits