electricity and circuit, class 6

 

Electricity                   class 6

 

·         Electricity is useful form of energy. it play very important role in our daily life it make our work easy.

·         It is needed for functioning of electric equipments like computer refrigerator air conditioner bulb and etc

Electric cell:  It is a common source of electric energy for many types of equipment it is used in calculators .remote, toy , camera etc

 

Advantage of electric cell

• ·         They are lightweight so they are portable
• ·         they produce a very small amount of electricity so safe for work
• ·         they are not very costly
• ·         they do not contain chemical liquid
• ·         they give study electric current

 

Dry cell: Dry cell is a source of electricity. it convert chemical energy into  electric energy. A dry cell is a very convenient source of electric current

A cell consist of an outer covering made up of zinc at the centre of container a carbon rod with a metallic cap made of brass is placed .this carbon rod  is surrounded by mixture of magnesium dioxide and powder charcoal (carbon), the remaining space inside zinc container is filled with thick paste of ammonium chloride NH₄Cl. the outer side of the zinc container is covered with cardboard and the base of zinc remain uncovered. the metallic cap act as positive terminal (+ve)and base of zinc container act as negative terminal(-ve).

• ·         dry cell is used in electrical clock, toys
• ·         button cell is used in watch.
• ·         Solar panels made up of solar cells are used to light up streets and many homes.

 

Battery : When two or more cells are connected and to and they form battery

 

Bulb: An electric bulb is a device which glows and emits light, when electric current is passed through it. So convert electric energy into light energy.

Bulb contain a thin tiny wire (made up of tungsten) inside the glass cover. This is called filament. It is supported by two thicker wires, as shown in Fig. 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 of the 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.

When an electric current is pass through the filament of bulb the filament become hot and emits light

 

fused bulb: If the filament of the bulb is broken, the circuit is not corhpleted 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.

 

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 form 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.

Electric current: the rate of flow of charge is known as current.

 

Electric switch: Electric switch is a simple device that either breaks the circuit or completes it to stop or start the flow of current.

·         When the switch completes the circuit, it is called closed switch.

·         When the switch breaks the circuit, it is called open switch.

 

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.

 

 Three basic conditions are required for an electric current to flow.

·         A device used to produce an electric current like cell, battery, or a plug point acting as a source.

·         A wire made of a metal like copper, silver, or aluminium, which will allow electric current to flow through easily.

·         An unbroken loop (of the wire) running from one terminal of the source, through various appliances, back to the other terminal of the source.

 

Making a Simple Electric Circuit:
When we connect the terminals of a pencil cell (name given to the cell due to its shape) to a bulb using two wires, the bulb glows. This happens because we provide a path for the current to flow. A path for an electric current to flow is called an electric circuit.

·         

·         In Figure 14.6(a), one wire from the pencil cell is connected to the torch bulb, while the other wire is not. The electric circuit is not complete here. In Figure 14.6(b), both the wires from the cell are connected to the torch bulb. The electric circuit is complete in this case. Electric current flows only if there is an unbroken path or closed circuit starting from one terminal of the source, through the torch bulb, to the other terminal of the source. Thus, the bulb glows in Figure 14.6(b) but not in Figure 14.6(a). The circuit in Figure 14.6(a) is not complete. Hence, current cannot flow through the circuit and the bulb does not glow. Such a circuit is called an open circuit. The circuit in Figure 14.6(b) is complete. Electric current flows through the circuit and, as a result, the bulb glows. Such a circuit is called a closed circuit.

 

 Electric Torch

A schematic diagram of an electric torch is shown in Fig. An electric torch has one or more dry cells inside it, which act as the ‘source’. These cells are connected through a switch to a small bulb. When the switch is pushed to the ‘on’ position, the circuit is complete and the bulb glows. When the switch is pushed to the ‘off’ position, the circuit is incomplete (broken). Now the current cannot flow through the circuit, and the light goes out.

There are 3 metal strips-  metal strip (A part of switch) metal strip B (connected to the metal case) metal strip C (connected to the spring ) meta strip B and C are fixed while metal strip a is pressed and made two slide

when the switch is pushed  to on position the metallic strip A is pushed forward so that it touches B and C  and the circuit is complete which glow the bulb. when the switch is supposed to off the contact between strip a and b broke and the circuit broke do not glow bulb.

 

Conductors

·         Materials through which electric current can flow are called conductors.

·         Most metals are conductors.

·         Our body is also a good conductor.

Insulators

·         Materials, through which the electric current cannot pass, are called insulators. In other words, insulators are the bad conductors of electricity.

·         Rubber and wood are insulators.

Electrical safety:

 

A person may get an electric shock because our body is a good conductor of electricity. some preventive measures to avoid electric shock are as follows:

• 1.    replace the light bulb only when it is switched off and cool
• 2.    never touch electrical switches or gadgets  when your body is wet( water is good conductor of electricity)
• 3.    don't try to repair or install electrical wiring or appliance
• 4.    do not touch electric poles and transformers on the road
• 5.    do not touch hanging wire on the road
• 6.    never fly kites near overhead power line
• 7.    never join the electric wires with bare hands