# Electric circuit and circuit diagram

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## 03 Electricity

#### ELECTRIC CIRCUIT

A continuous conducting path consisting of wires and other resistances (like electric bulb, etc.) and a switch, between the two terminals of a cell or a battery along which an electric current flows, is called a circuit.

It is a continuous and closed loop or path of electric current. The path consists of conductors or wires and battery or source. The direction of electric current is taken as opposite to the direction of the flow of electrons, which are negative charges.

Electricity could be lethal if not handled carefully and can cause deaths. Faulty wires or electric circuits can cause fire that should not be extinguished by water. Such fires require special extinguishers. So, electric live wires, sockets, electric poles, transformers and some electrical equipments need proper insulation. Although the voltage of a small bettry is of the order of volts, a transformer may be upto 11000 V and such equipments are often marked with danger signs and are kept out of reach of children.

The two terminals of an electric battery should not be connected together without a load or bulb, because the chemicals inside the battery react very quickly and can generate an immense amount of energy. This can even cause the battery to burst.

A continuous conducting path consisting of wires or copper conductors and other resistances (like electric bulb, etc.) and a switch, between the two terminals of a cell or a battery is called a circuit. The battery or cell is the power source. One end of the conductor is connected to one terminal of the power source and the other end to the other terminal of the power source through the load. The switch can be used to open or close a circuit.

#### SYMBOLS FOR ELECTRICAL COMPONENTS (OR CIRCUIT SYMBOLS)

1. A cell:It provides the source of current. In its symbol, the larger terminal is positive, whereas the smaller one is the negative terminal.
2. A battery:It is a combination of cells and its utility is same as the cell.
3. Wire joint:One device may be connected to the other using wires. This is shown by drawing ‘blobs’ at their point of connectivity.
4. Wires crossing without joining:The wires that do not touch each other are drawn without blobs. The following figure shows how the unjoined wires are represented.
5. Switch:It is a plug key used to allow or stop the flow of current upon being pressed. It may be an open or a closed switch.
6. Electric bulb:The electrical device which uses electricity to glow.
7. Resistor (R):It is used to restrict the amount of current flow in the circuit.
8. Variable resistance:Also known as the rheostat, it is used to regulate the amount of current flow by increasing or decreasing the resistance to the current flow.
9. Ammeter:It is used to measure the current passing at a particular point.
10. Voltmeter:It is used to measure the voltage between two points in a circuit.
11. Galvanometer: Galvanometer: It is a device to detect current in an electric circuit.

#### CIRCUIT DIAGRAM

• A circuit diagram is a simplified representation of the components of an electrical circuit.
• The various components are represented using standard symbols or images of the distinct parts.
• The connections of the various elements and their relative positions are indicated in a circuit diagram.
• A typical circuit diagram consists of:
• A voltage source or battery
• A load for example, light bulb or resistor which requires electricity from source
• A conductor which allows movement of charge through it like a copper wire.
• In addition there may be other components as per requirements.