Let Us Recapitulate

1. Power station: Electricity that we uSe at homes, in our factories, is supplied from a power station.

2. Electric cell: Electric cell is a source of electricity.

3. Production of electricity in a cell: An electric cell produces a small amount of electricity from chemicals stored inside it. When the chemicals in the electric cells are used up, the electric cells stop I, producing electricity.

4. Terminal: All types of electric cells have two terminals, a positive terminal and a negative terminal. In a dry cell used in our homes, the central carbon rod is the positive (+) terminal and the zinc contained is the negative (–) terminal.

5. Battery: When two or more cells are joined together, the combination is called a battery.

6. Bulb: We get light from a thin tiny wire inside the glass cover. This is called filament. It is supported by two thicker wires. One of these thick wires is connected to the metal casing around the base of the bulb. The other is connected to the metal tip of the base. The base of the bulb and the metal tip ofthe base are the two terminals of the bulb. These two terminals are fixed in such a way that they do not touch each other.
The inside portion of the bulb is filled up with inert gases, like argon.

7. Circuit: The complete path, from one terminal of the electric cell through the bulb and back to the other terminal of the electric cell, is called a circuit.  Open circuit: If there is any gap in the path of a circuit, the bulb does not light up. Such a circuit is called an open circuit.
Closed circuit: The bulb lights up only when a bulb and wire fonn a complete path, which starts at one terminal of electric cell and ends at the other terminal. Such a circuit is called a closed circuit.

8. Flow of current in a circuit: As soon as the path from one terminal of electric cell to the other is completed, an electric current starts flowing through the circuit and the bulb lights up. The electric current flows from the positive terminal of the electric cell to its negative terminal.

9. In the bulb, current enters through one of its terminals, flows through the filament. InsIde the bulb and comes out through the other terminal of the bulb. When the current flows through the filament, it starts glowing.

10. Fused bulb: Ifthe filament of the bulb is broken, the circuit is not completed and hence the current cannot flow. The bulb with broken filament is called a fused bulb. When a bulb gets fused, it does not light up.

11.    Electric switch: Electric switch is a simple device that either breaks the circuit or completes it to stop or start the flow of current.
(i)    When the switch completes the circuit, it is called closed switch.
(ii)    When the switch breaks the circuit, it is called open switch.

12.    Conductors
(i) Materials through which electric current can flow are called conductors.
(ii) Most metals are conductors.
(iii) Our body is also a good conductor.

13.    Insulators
(i) Materials, through which the electric current cannot pass, are called insulators. In other words, insulators are-the bad conductors of electricity.
(ii) Rubber and wood are insulators.

14.    Conduction tester: It is a simple device to test whether a material is a conductor or insulator.

15.    Filament: The thin wire that gives off light is called the filament of the bulb.

16.    Dry cell: Dry cell is a source of electricity. It generates direct current (DC) due to chemical reaction that takes place inside it.

Keywords

1.    Bulb: An electric bulb is a device which glows and emits light, when electric current is passed through it.
2.    Conductors: Materials that allow electric current to pass through them are called conductors.
3.    Electric cell: Electric cell is a source of electricity.
4.    Electric circuit: The complete path from one terminal of the electric cell through the bulb and back to other terminal of the electric cell is called an electric circuit.
5.    Filament: In electric bulb, there is a thin tiny wire inside the glass cover. This is called filament.
6.    Insulator: Materials that do not allow electric current to .pass through them are called insulators.
7.    Switch: Electric switch is a simple device that either breaks the circuit or completes it to stop or start the flow of current.
8.   Terminal: All types of electric cells have two terminals, a positive terminal and a negative terminal.