A circuit diagram is a graphical representation of an electrical circuit. A schematic diagram shows the components and interconnections of the circuit using standardized symbolic representations while a pictorial circuit diagram uses simple images of components. Unlike a block diagram or layout diagram, a circuit diagram shows the actual electrical connections.
Before talking about a circuit diagram, let us recall circuits. An electrical circuit is a device which provides the complete path for current to flow. A circuit consists of three basic things to function:
- A source of voltage
- A conductive path which facilitates the movement of charges
- A resistor (say, a light bulb) which requires electricity to do work
Apart from the basic requirements, a circuit consists of a number of components which provide different functionalities.
What is a Circuit Diagram?
A circuit diagram is a simplified representation of the components of an electrical circuit using either the images of the distinct parts or standard symbols. It shows the relative positions of all the elements and their connections to one another. It is often used to provide a visual representation of the circuit to an electrician. The following figure shows a simple circuit diagram.
Components of Circuit Diagram
Let us learn about some of the important components of circuits and their symbols in a circuit diagram.
- An electric cell: It provides the source of current. In its symbol, the larger terminal is positive, whereas the smaller one is the negative terminal.
- A battery: It is a combination of cells and its utility is the same as the cell.
- 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.
- Wire joint: One device may be connected to the other using wires. This is shown by drawing ‘blobs’ at their point of connectivity.
- 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.
- Electric bulb: The electrical device which uses electricity to glow.
- Resistor (R): It is used to restrict the amount of current flow in the circuit.
- 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.
- Ammeter: It is used to measure the current passing at a particular point.
- Voltmeter: It is used to measure the voltage between two points in a circuit.
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