Electrical symbols

Electrical symbols By Muhammad Ahtsham

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Muhammad Ahtsham

Electrical Symbols


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1890 and 1910, knob and tube wire was all the rage in home building.

History of electrical wiring


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In the 1920's to 1940's, electrical took a turn to a more protective wiring scheme, flexible armored cable used to use. It is also known as Greenfield. It was a welcomed addition to home wiring.



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In the 1940's, finally came the age of metal conduit. This invention allowed to pull many wires in the same enclosure.


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The newest addition to wiring was introduced in the 1960's around 1965. It was an update to NM cable that incorporated the use of a third wire, a bare ground wire run with a hot and neutral wire.


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Underground feeder wire(UF) was invented to be buried directly under the ground without having to be placed in conduit.


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A wire is a single flexible strand or rod of metal. Wires are used to pass current very easily from one part of the circuit to another.

Wire

Wire Junction

Wire Not connected


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It supplies electrical energy. The larger terminal (on the left) is positive (+) while the smaller (on the right) is negative (-). A single cell is often called a battery, but strictly the battery is two or more cell joined together.

Cell


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It converts light energy into electrical energy.

Solar Cell


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A battery supplies electrical energy to the circuit. It is like cell but the difference is that cell is considered as one but the battery is considered more than one cell.

Battery

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It provides the light when electric current passes through it. A light bulb produces light with a filament wire heated to a high temperature by an electric current passing through it until it glows.

Bulb


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Fuse

A fuse is a special kind of resistor that acts as short circuit (0 resistances) unless the current exceeds the rated value. If the current exceeds a rated value the fuse blows and acts as an open circuit (an infinite resistance).


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The circuit breaker is a The circuit breaker is a mechanical switching device capable of protecting the circuit wiring, capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as short circuit.

Circuit Breaker



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(a).It is the lighting lamp transducer which converts electrical energy to light. This symbol is used for a lamp providing illumination.

e.g. A car head lamp or torch bulb.

b. It is the indicating transducer that converts electrical energy to light. This symbol is used for a lamp which is an indicator.

e.g. A warning light on cars dashboard

Lamp


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A device which is only allows current to flow in one direction.

It has low (ideally zero) resistance to current flow in one direction, and high (ideally infinite) resistance in the opposite direction.

Diodes


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It is a light sensitive diode.

Photodiode allows current flow when exposed to light.

A photodiode is capable of converting light into

either current or voltage, depending upon the mode of operation

Photo diode


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(1). Fixed power source: The free DC output is fixed to a constant voltage level by using a voltage controller. If it is used to produce DC, a rectifier is used to convert alternating voltage to direct voltage.

(2). Variable power source: An AC power supply typically takes the voltage from mains supply and lowers it to the desired voltage

Power source

FIXED

Variable


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Resistor

Fixed Resistor: This type of resistor resists the flow of current.

Variable Resistor: This type of resistor is used to control the current known as rheostat.

Variable Resistor Potentiometer: This type of resistor consist of 3 contacts. It is used to control the voltage.

Variable resistor Preset: Preset resistors are used in circuits when it is necessary to alter the resistance.

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3

4


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AC CURRENT SOURCE:

AC is the form in which electric power is delivered to businesses and residences. In alternating current the flow of electric charge continually changes the direction.


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DC CURRENT SOURCE:

Direct current (DC) is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries, thermocouples, solar cells.

Direct current is used to charge batteries, and in nearly all electronic systems, as the power supply.


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LED

LED stands for (light emitting diode). It is a semi-conductor light source. LED’s are used in general lightning, traffic signals and are used in advance communication technology.


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LDR stands for (light dependent resistor) made up of semi conductor, they are useful in light/dark sensor circuits. Normally the resistance of an LDR is very high, sometimes as high as

1000000 ohms, but when they are illuminated with light resistance drops dramatically.

LDR


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An electric heater is an electrical appliance that converts electrical energy into heat. The heating element inside every electric heater is simply an electrical resistor, and works on the principle of Joule heating.

HEATER


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An electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric current to flow through an external circuit. The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine.

GENERATOR


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An electric motor is an electric machine that converts electrical energy into mechanical energy.

In normal motoring mode, most electric motors operate through the interaction between an electric motor's magnetic field and winding currents to generate force within the motor.

MOTOR


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A transformer is a static electrical device that transfers energy by inductive coupling between its winding circuits. A varying current in the primary coil creates a varying magnetic flux in the transformer's core and thus a varying magnetic flux through the secondary coil.

This varying magnetic flux induces a varying electromotive force (emf) in the secondary coil. Transformers can be used to vary the relative voltage of circuits or isolate them, or both.

Transformer


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RCD

A residual - current device (RCD) is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor.


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Light tubes are physical structures used for transporting or distributing natural or artificial light for the purpose of illumination. In their application to day lighting, they are also often called tubular day lighting devices, sun pipes, sun scopes, or daylight pipes.

TUBE LIGHT


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Electronic sirens are basically high-performance electronic amplifiers like in home sound systems. These sirens work with substantially higher outputs and specific demands are placed on them in terms of desired extreme reliability and different methods of their control.

SIREN or HORN


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A solder bridge is an electrical connection between two conductors by means of a small blob of solder. Solder mask is not always used for hand soldered assemblies but is essential for mass produced boards that are soldered automatically using reflow or solder bath techniques.

SOLDER BRIDGE


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A thermocouple is a temperature-measuring device consisting of two dissimilar conductors that contact each other at one or more spots.

It produces a voltage when the temperature of one of the spots differs from the reference temperature at other parts of the circuit. Thermocouples are a widely used type of temperature sensor for measurement and control.

THERMO COUPLE


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Ground or earth can refer to the reference point in an electrical circuit from which voltages are measure. A common return path for electric current or a direct physical connection to the Earth.

GROUND

SIGNAL GROUND

Chess ground


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A loudspeaker is an electro acoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems but electronic amplification by vacuum tube made loudspeakers more generally useful.

LOUD SPEAKER


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An electric bell is a mechanical bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing or clanging sound. Electric bells have been widely used at railroad crossings, in telephones, fire and burglar alarms, as school bells, door bells, and alarms in industrial plants.

BELL


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Switches1. Push switch: A push switch allows

current to flow only when the button is pressed like switch in door bell.

2. Push to break switch: This type of switch is normally closed i.e. on. It is open only when button is pressed.

3. SPST: Single Pole, single Throw: An on—off switch allows current to flow only when it is closed.


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Switches

4. SPDT: Single Pole, Double Throw: They are described as on off on switch.

5. DPST: Double Pole, single Throw: A dual on off switch often used to switch main electricity.

6. DPDT: Double Pole, Double Throw: They are used in motors.


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Electrical symbols

Engineering

Transcript of Electrical symbols