Circuit symbols are used in circuit diagrams to show how a circuit is connected. The actual layout of the components is usually quite different from the circuit diagram. To build a circuit, you need a different diagram showing the layout of the parts on a breadboard (for temporary circuits), stripboard, or printed circuit board.
Understanding Circuit Symbols is essential for every electronics student. With structured lessons, interactive examples, and expert guidance, students can master circuit diagrams step by step through a modern online learning experience designed to make complex topics simple and practical.
Wire and Connection
Wire
In a circuit diagram, a Wire is the most basic component, representing a conductive path (usually copper) that allows electricity to flow between components. It is represented by a simple solid straight line.
Wires joined
A 'blob' should be drawn where wires are connected (joined), but it is sometimes omitted. Wires connected at 'crossroads' should be staggered slightly to form two T-junctions, as shown on the right. wires crossing but not joined symbol
Wires not joined
In complex diagrams, it is often necessary to draw wires crossing even though they are not connected. The simple crossing on the left is correct, but may be misread as a join where the 'blob' has been forgotten. The bridge symbol on the right leaves no doubt!
Power Supply Symbols
Cell
Supplies electrical energy. The larger line is positive (+). A single cell is often called a battery, but strictly speaking, a battery is two or more cells joined together.
Battery
A Battery is a power source consisting of two or more electrochemical cells connected to provide electrical energy. Its circuit symbol is composed of multiple pairs of parallel lines (long and short) to represent the combined cells.
Solar Cell
A Solar Cell (also known as a Photovoltaic Cell) is a device that converts light energy directly into electrical energy. Its circuit symbol is similar to a battery cell but is enclosed in a circle with arrows pointing toward it to represent incoming sunlight.
DC supply
A DC Supply (Direct Current) is a power source that provides a constant voltage in one direction. In circuit diagrams, it can be represented by two parallel lines of unequal length (the symbol for a single cell) or a circle with “+” and “–” signs.
AC supply
An AC Supply (Alternating Current) is a power source where the flow of charge periodically reverses direction. In a circuit diagram, it is represented by a circle containing a sine wave (∼), which symbolizes the oscillating nature of the voltage.
Fuse
A Fuse is a safety device designed to protect an electrical circuit from excessive current. Its circuit symbol is a rectangle with a single wire passing through the centre.
Transformer
Two coils of wire linked by an iron core. Transformers are used to step up (increase) and step down (decrease) AC voltages. Energy is transferred between the coils by the magnetic field in the core; there is no electrical connection between the coils.
Earth (Ground)
A connection to earth. For some electronic circuits, this symbol is used for the 0V (zero volts) of the power supply, but for mains electricity and some radio circuits, it really means the earth. It is also known as ground.
Output Device Symbols
Lamp (lighting)
A transducer which converts electrical energy to light. This symbol is used for a lamp providing illumination, for example, a car headlamp or torch bulb.
Lamp (Indicator)
A transducer which converts electrical energy to light. This symbol is used for a lamp which is an indicator, for example, a warning light on a car dashboard.
Heater
A Heater (or heating element) is a passive component that converts electrical energy into heat through the process of Joule heating. In a circuit diagram, it is typically represented by a rectangular box with a zigzag line inside or simply a long, narrow rectangle.
Motor
A DC Motor is a device that converts electrical energy into mechanical energy (rotation). In a circuit diagram, its symbol is a circle with the letter “M” inside.
Bell
An Electric Bell is a device that converts electrical energy into sound using an electromagnet. Its circuit symbol resembles a bell or a “mushroom” shape on its side.
Buzzer
A transducer which converts electrical energy to sound.
Inductor, Coil, Solenoid
A coil of wire which creates a magnetic field when current passes through it. There may be an iron core inside the coil. It can be used as a transducer converting electrical energy to mechanical energy by pulling on something magnetically.
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Switch Symbols
push-to-make switch symbol
Push-to-make Switch
A Push-to-make switch (also known as a Normally Open or NO momentary switch) is designed to stay disconnected until the button is physically pressed. When the button is pushed, it closes the circuit and allows current to flow.
Push-to-break Switch
A Push-to-break switch (also known as a Normally Closed or NC momentary switch) is designed to stay connected until it is pressed. When you push the button, the internal contact is broken, and the circuit opens. This type of push switch is normally closed = on, it is open = off only when the button is pressed.
SPST, On-Off Switch
SPST = Single Pole, Single Throw. Current flows only when the switch is in the closed =on position.
SPDT, 2-way Switch
SPDT = Single Pole, Double Throw. A 2-way changeover switch directs the flow of current to one of two routes according to its position. Some SPDT switches have a central off position and are described as 'on-off-on'.
DPST Switch
DPST = Double Pole, Single Throw. A dual on-off switch, which is often used to switch mains electricity, because it can isolate both the live and neutral connections.
DPDT Switch
DPDT = Double Pole, Double Throw
A Double Pole Double Throw (DPDT) switch is essentially two separate switches (poles) that are controlled by a single mechanism. Each pole can be connected to one of two different terminals (throws).
Relay
An electrically operated switch, for example, a 9V battery circuit connected to the coil, can switch an AC mains circuit. The rectangle represents the coil.
NO = Normally Open, COM = Common, NC = Normally Closed.
Resistor Symbols
Resistor
A resistor restricts the flow of charge. Uses include limiting the current passing through an LED and slowly charging a capacitor in a timing circuit. Some publications use the old resistor symbol: the old zig-zag resistor symbol.
Rheostat Variable Resistor
A rheostat has 2 contacts and is usually used to control current. Uses include controlling lamp brightness or motor speed and changing the rate of flow of charge into a capacitor in a timing circuit.
Potentiometer Variable Resistor
A potentiometer has 3 contacts and is usually used to control voltage. It can be used like this as a transducer converting position (angle of the control spindle) to an electrical signal.
Preset Variable Resistor
A preset is operated with a small screwdriver or similar tool. It is designed to be set when the circuit is made and then left without further adjustment. Presets are cheaper than standard variable resistors, so they are sometimes used in projects to reduce the cost.
Capacitor Symbols
Understanding capacitor and semiconductor symbols is essential for mastering circuit diagrams. With structured online lessons, expert tutors, and step-by-step guidance, students can easily learn GCSE physics how these components work in real circuits and exams.
Capacitor & Unpolarised
A capacitor stores electric charge. It can be used with a resistor in a timing circuit, for smoothing a supply (it provides a reservoir of charge) and can be used as a filter (blocking DC signals but passing AC signals). Unpolarised capacitors usually have small values, less than 1µF.
Capacitor & Polarised
A capacitor stores electric charge. Polarised capacitors must be connected the correct way round. They usually have larger values, 1µF and greater. See above for uses.
Variable Capacitor
A variable capacitor is used in a radio tuner.
Trimmer Variable Capacitor
A Trimmer Variable Capacitor (also known as a "Trimmer") is a specialized variable capacitor used for initial calibration or occasional tuning of a circuit. Unlike a standard variable capacitor with a knob, a trimmer is typically adjusted with a small screwdriver and is intended to be set and left in place.
Diode Symbols
Diode
A Diode is a two-terminal electronic component that primarily conducts current in one direction. Its symbol is a triangle pointing toward a vertical line, representing the direction of conventional current flow.
Light Emitting Diode
A Light Emitting Diode (LED) is a semiconductor light source that emits light when current flows through it. Its circuit symbol is a standard diode with two arrows pointing away from the device, representing the emission of light.
Zener Diode
A Zener Diode is a special type of diode designed to reliably allow current to flow “backwards” when a certain set reverse voltage, known as the Zener voltage, is reached. Its circuit symbol is similar to a standard diode but with "bent" ends on the cathode bar, resembling the letter 'Z'.
Photodiode
A Photodiode is a semiconductor device that converts light into electrical current. Its circuit symbol consists of a standard diode symbol with two arrows pointing toward the device to indicate incoming light.
Transistor NPN
A transistor amplifies current and can be used with other components to make an amplifier or switching circuit. This symbol is for a bipolar junction transistor (BJT), the type you are most likely to use at first.
Transistor PNP
A transistor amplifies current and can be used with other components to make an amplifier or switching circuit. This symbol is for a bipolar junction transistor (BJT), the type you are most likely to use at first.
Phototransistor
A Phototransistor is a light-sensitive transistor. It functions similarly to a standard transistor but uses light instead of (or in addition to) base current to control the flow of electricity between the collector and emitter.
Audio and Radio Symbols
In audio and radio electronics, symbols represent components that either convert electrical signals into sound (or vice versa) or handle high-frequency electromagnetic waves.
Microphone
A Microphone is a transducer that converts sound waves (acoustic energy) into electrical signals. In a circuit diagram, it is typically represented by a circle with a small internal line or “diaphragm” and two connecting leads.
Earphone
An Earphone (or headphone) is a small transducer designed to be held close to the ear. Its symbol looks like a simplified version of a head-mounted speaker.
Loudspeaker
A Loudspeaker converts electrical signals into audible sound waves for a larger area. The symbol mimics the physical cone and magnet structure of a speaker.
Piezo Transducer
A Piezo Transducer (often used as a high-frequency “tweeter” or a simple beeper) uses the piezoelectric effect to create sound. Its symbol features a crystal-like structure inside a circle.
Amplifier (General Symbol)
An Amplifier increases the amplitude (power/voltage) of an input signal. It is universally represented by a triangle pointing in the direction of the signal flow.
Aerial (Antenna)
An Aerial or Antenna is a transducer that converts radio frequency (RF) electric current into electromagnetic waves (and vice versa).
Meters and Oscilloscope
In electrical schematics, meters are used to measure specific properties of a circuit, while an oscilloscope is used to visualize how those properties (usually voltage) change over time. Most meter symbols follow a standard format: a circle with a letter inside representing the unit of measurement.
Voltmeter
Measures voltage. The proper name for voltage is 'potential difference', but voltage is more widely used.
Ammeter
An Ammeter is an instrument used to measure the flow of electrical current in a circuit. In a schematic diagram, it is represented by a circle with a capital “A” inside.
Galvanometer
A Galvanometer is a highly sensitive instrument used to detect and measure very small amounts of electrical current. Unlike a standard ammeter, which is designed for higher current loads, a galvanometer is often used to determine the presence and direction of a tiny current in a circuit.
Ohmmeter
An Ohmmeter is an instrument used to measure electrical resistance (R), which is the opposition to current flow in a material. In a circuit diagram, it is represented by a circle with the Greek letter Omega (Ω) inside.
Oscilloscope
An oscilloscope is used to display the 'shape' of electrical signals - showing how they vary with time. It can be used to measure voltage and time periods.
Sensors (input devices)
Sensors are the “eyes and ears” of a circuit, reacting to environmental changes by altering their electrical properties. Both the LDR and the Thermistor are passive components whose resistance changes based on external stimuli.
LDR
A transducer which converts brightness (light) to resistance (an electrical property). LDR = Light Dependent Resistor
Thermistor
A Thermistor is a type of resistor whose resistance is strongly dependent on temperature. The name is a portmanteau of “thermal” and “resistor.”
Logic Gate Symbols
Logic gates process signals which represent true (1, high, +Vs, on) or false (0, low, 0V, off). For more information, please see the page on logic gates. The symbols shown here are the traditional ones for logic gates, as these are the most widely used symbols.
NOT
A NOT gate can only have one input. The “o” on the output means 'not'. The output of a NOT gate is the inverse (opposite) of its input, so the output is true when the input is false. A NOT gate is also called an inverter.
Buffer
A Buffer Gate (also known as a "YES Gate") is a logic gate that passes its input to its output without inversion. If the input is 1, the output is 1. If the input is 0, the output is 0.
AND
An AND gate can have two or more inputs. The output of an AND gate is true when all its inputs are true.
NAND
A NAND gate can have two or more inputs. The 'o' on the output means 'not', showing that it is a NOT AND gate. The output of a NAND gate is true unless all its inputs are true.
OR
An OR gate can have two or more inputs. The output of an OR gate is true when at least one of its inputs is true.
NOR
A NOR gate can have two or more inputs. The “o” on the output means 'not', showing that it is a NOT OR gate. The output of a NOR gate is true when none of its inputs is true.
EX-OR
An EX-OR gate can only have two inputs. The output of an EX-OR gate is true when its inputs are different (one true, one false).
EX-NOR
An EX-NOR gate can only have two inputs. The “o” on the output means “NOL”, showing that it is a NOT EX-OR gate. The output of an EX-NOR gate is true when its inputs are the same (both true or both false).
In the End
Mastering circuit symbols is the first step toward confidently designing, building, and troubleshooting electronic circuits. From basic components like resistors and capacitors to advanced devices such as transistors and logic gates, understanding their symbols allows students to read schematics accurately and turn ideas into real, working projects.
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FAQs
Why are circuit symbols important in electronics?
Circuit symbols provide a universal language for engineers and students. They make it possible to understand, design, and troubleshoot circuits without seeing the physical components.
How can online tutoring help me understand circuit symbols better?
Online tutoring provides structured lessons, one-to-one guidance, and practical problem-solving support. With expert help, students can clarify doubts quickly, practice real exam-style questions, and build confidence in reading and drawing circuit diagrams accurately.
Are circuit symbols the same worldwide?
Most circuit symbols follow international standards, but slight variations may exist between American and European notation. However, their functions remain the same.
How can beginners start learning circuit diagrams?
Beginners should start by memorising basic symbols (resistor, battery, switch, diode) and then practice reading simple schematic diagrams before moving to complex circuits.
What is the difference between a schematic diagram and a wiring diagram?
A schematic diagram shows how components are electrically connected using symbols, while a wiring diagram shows the physical layout and actual wire connections.
Do I need to memorise all circuit symbols?
No, but you should understand commonly used symbols. With regular practice, recognising them becomes natural.
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