Have you ever seen lightning during a thunderstorm at night It's quite a sight to see! Lightning is a flow of electric charge from clouds to the ground, which is called an electric current. Lightning bolts carry a lot of energy, which is how we first learned about energy being transferred by electric currents.
Electricity is used in our everyday lives and comes from power stations. It travels through substations and into our homes, where it's used to power our appliances. Each appliance has an electric circuit that controls how it operates and uses electrical energy. Engineers and electricians use circuit diagrams to understand how to build or repair these devices. Circuit diagrams are pictures that show the connections between components in the electric circuit. Each electrical component has a symbol to differentiate it from the others, and these symbols are called circuit symbols. Check out the example below to see a simple electric circuit with circuit symbols for different components.
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A circuit needs a source of energy to have an electric current. This energy comes from a power supply, which is often a cell or battery. A cell changes chemical potential energy into electric potential energy, allowing a current to flow through the circuit. The circuit symbol for a cell has two parallel lines. One line is longer than the other, indicating the positive terminal of the cell. The shorter line represents the negative terminal. Check out the figure below to see the circuit symbol for a cell.
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Note that the positive terminal is generally marked by a + symbol, but if it isn't, it is assumed that the person reading the diagram knows that the longer line represents the positive terminal.
A battery consists of two or more cells that are connected in series in a circuit. The combination of cells can provide greater electrical energy than a single one of the cells. The symbol for a battery is simply the symbol for a cell repeated, as shown in the figure below.
A switch is used in an electric circuit to break the wires in a circuit or join them. An open switch does not allow current to flow and when the switch is closed a current can flow again. The symbols for an open switch and closed switch are shown in the figure below.
A lamp, also called a bulb, is a device that emits light when an electric current passes through it. It can be used as a simple test to tell if a current is passing through part of a circuit, or for illumination. The circuit symbol for a lamp is a cross within a circle as provided in the figure below.
A resistor is a device that resists the flow of current. A fixed resistor has a value of resistance (measured in ohms) that does not change and will provide constant resistance to the flow of current. The symbol for a fixed resistor is a rectangle as shown in the following figure.
An ammeter is an instrument used to measure the current in an electric circuit. It is always connected in series with the device through which the current is to be measured. The circuit symbol for an ammeter is represented by the letter A inside a circle, as in the following figure.
A voltmeter is an instrument used to measure the potential difference between two points in an electric circuit. As such, it is always connected in parallel between the two points of interest. The circuit symbol for a voltmeter is the letter V contained within a circle as shown in the figure below.
A variable resistor is a type of resistor whose resistance can be varied. It can therefore be used to vary the current in a circuit. The symbol for a variable resistor is similar to that for a resistor but an arrow passes through the rectangle as is shown in the following figure.
A fuse is a device that will melt when the current passes a certain value. The circuit will then become open and no current can flow through it. Different fuses have different current ratings. They prevent the current from surpassing a value (their rating) that would damage other circuit components. The symbol for a fuse is similar to that for a resistor with a horizontal line passing through the rectangle. The circuit symbol is shown in the figure below.
A diode is a component that only allows current to flow in one direction in a circuit. If the current flows in the opposite direction, it cannot flow past the diode. The diode circuit symbol is an arrow that points in the direction in which current is allowed to flow. This is shown in the figure below.
A light-emitting diode (LED) is a type of diode that allows current to only pass through it in one direction and when a current passes through it, it will emit light. Many LEDs can be used for illumination whereas a single LED can be used to indicate a current passing through an electrical component. The symbol is similar to the diode symbol but with outward-pointing arrows to indicate that light is emitted, as seen in the next figure.
A light-dependent resistor (LDR) is a variable resistor whose resistance varies with the intensity of light that is incident on it. LDRs have a higher resistance in low-intensity light conditions (dim light) and have lower resistance in high-intensity light (bright light). Its symbol is similar to the resistor, but the rectangle is surrounded by a circle and inward-pointing arrows indicate the incoming light, as in the below figure.
A thermistor is another type of variable resistor whose resistance changes with temperature. The most common type of thermistor is the negative temperature coefficient thermistor, whose resistance decreases when the temperature increases and its resistance increases when the temperature decreases. It has a similar symbol to a resistor but with a line through the rectangle as shown in the following figure.
The following example will test your knowledge of the circuit symbols that were discussed in this article.
The correct labels are as follows:A → CellB → Open switchC → DiodeD → AmmeterE → Thermistor
Circuit Symbols - Key takeaways Electric Circuits have corresponding diagrams that depict the flow of current through the various devices/appliances in that circuit. These diagrams are known as circuit diagrams. A circuit diagram contains circuit symbols that identify various circuit components. Each component has a unique circuit symbol. It is important to be able to identify and draw circuit symbols for the following components: Cell Battery Open switch Closed switch Lamp Fixed resistor Ammeter Voltmeter Variable resistor Fuse Diode Light-emitting diode (LED)Light-dependent resistor (LDR)Thermistor
What are the circuit symbols?
They are the symbols given to electrical components in order to differentiate them from each other in a circuit diagram.
What are the most common circuit symbols?
The most common circuit symbols are those used for the cell, battery, switch, resistor, ammeter, voltmeter, lamp, fuse, diode and LED.
What are the 5 parts of a circuit?
The 5 parts of a circuit are the power source, conductor, switch, load and any other component (capacitor, transistor, etc.).
Why do we use circuit symbols?
We use circuit symbols to differentiate circuit components from each other in a circuit diagram.
What is the name of symbols used in wiring circuits?
The name we give to the symbols used to represent circuit components is 'circuit symbols'.
