Electrical symbols information: A Primer

“Do-It-Yourselfers” sometimes find themselves scratching their heads when electrical symbols information suddenly pop up on an instruction sheet or on a blueprint or chart. Yes, a legend is supplied – hopefully. But the terms used on that legend are likely not familiar to the average homeowner. Enrolling in an electricians class is usually not an option, so what is the best way forward? Let’s start at the beginning; familiarize yourself with the basic vocabulary you are sure to encounter but may need to brush up on. Terms are grouped by kind and in alphabetical order.


Transducer and Amplifiers

Transducer:  A transducer is used to change energy from one form to another.  A solar panel is a transducer; it changes solar energy to electricity.

Piezo transducer: A specific transducer that converts energy to sound; think of a doorbell.

Amplifier: An amplifier is used to increases the voltage, current, or power of a signal.



Capacitor: A capacitor stores an electric charge –like a battery. Though a capacitor does not produce new electrons, like batteries do.

Polarized Capacitor: A polarized capacitor has a positive terminal and a negative terminal.

Variable Capacitor: A variable capacitor is used in a radio tuner.

Trimmer Capacitor: A trimmer capacitor is a special kind of variable capacitor; it is permanently configured when created.



Diode: A diode controls the direction of the flow of electric energy.

LED (Light Emitted Diode): A semi-conductor diode that creates light.

Zener diode: A semi-conductor diode that has a special use; to regulate currents.

Photodiode: Simply a diode that is sensitive to light.


Meter: A meter simply measures something.

Voltmeter: A voltmeter measures voltage.

Anmeter: An ammeter measures currents.

Galvanometer: A galvanometer measures small currents.

Oscilloscope: An oscilloscope displays the shape of electrical signals and it can be used to measure their voltage.


Output Devices

Inductor: A coil of wire that creates a magnetic field when current passes through it.

Motor: A transducer that changes electrical energy into kinetic energy (motion).

Buzzer: A transducer that changes electrical energy into sound.



DC: DC stands for “direct current”. A direct current is always flowing in one direction.

AC: AC stands for alternating current. An alternating current always changes direction.

Transformer: A transformer refers to two wire coils that are connected by an iron core. Transformers are used to increase and step decrease AC voltages.

Ground: In electronics, a “ground” is an actual connection to the earth


Resistor: A resistor constrains the flow of current, for example to limit the current passing through an LED.

Variable Resistor: This type of variable resistor is usually used to control currents. They are used, for example, to control the brightness of a lamp.



Transistor: A transistor makes currents stronger. It can be used with other components to make an amplifier or switching circuit.

Phototransistor: A phototransistor is a light-sensitive transistor.


To Wrap Up

Review these terms before attempting to decipher the electrical symbol  information scattered all over your electrical diagram – you will know your diodes from your capacitors.