Electrical Symbols Chart: Complete Reference Guide

Electrical symbols are the standardized graphical shorthand used in circuit diagrams, wiring diagrams, and schematics. Knowing these symbols is essential for reading and drawing electrical diagrams. This comprehensive reference guide covers symbols for residential wiring, electronics, industrial controls, and power systems, organized by category with IEC and ANSI variations noted.

Symbol Standards: IEC vs ANSI

Two major standards define electrical symbols:

• IEC (International Electrotechnical Commission): Used internationally, especially in Europe, Asia, and Australia. Defined in IEC 60617.
• ANSI/IEEE (American National Standards Institute): Used primarily in North America. Defined in ANSI Y32.2 (IEEE 315).

The differences are mostly cosmetic (for example, the IEC resistor is a rectangle while the ANSI resistor is a zigzag), but the electrical meaning is the same.

Power Source Symbols

Batteries

• Single cell: Two parallel lines -- long line is positive (+), short line is negative (-)
• Multi-cell battery: Multiple alternating long/short lines
• Battery with value: Label shows voltage (e.g., 9V, 12V)

Voltage Sources

• DC voltage source: Circle with + and - signs inside
• AC voltage source: Circle with a sine wave (~) inside
• Controlled voltage source: Diamond shape with + and - signs

Current Sources

• DC current source: Circle with an arrow indicating current direction
• Controlled current source: Diamond shape with an arrow

Ground Symbols

• Earth ground: Three horizontal lines decreasing in width
• Chassis ground: Three diagonal lines from a horizontal line
• Signal ground: Single line with a triangle

Resistor Symbols

• Fixed resistor (ANSI): Zigzag line (typically 4-6 peaks)
• Fixed resistor (IEC): Rectangle
• Variable resistor / Potentiometer: Resistor with an arrow through it (or a third terminal with arrow)
• Thermistor: Resistor with a T through it
• Photoresistor (LDR): Resistor with arrows pointing toward it (light)
• Heater: Resistor with radiating lines

Capacitor Symbols

• Fixed capacitor: Two parallel lines with a gap
• Polarized capacitor (electrolytic): One straight line and one curved line (curved = negative)
• Variable capacitor: Capacitor with an arrow through it
• Trimmer capacitor: Capacitor with a diagonal arrow

Inductor Symbols

• Inductor (ANSI): Series of loops or bumps (4-5 humps)
• Inductor (IEC): Filled rectangle or series of arcs
• Iron core inductor: Inductor with parallel lines alongside (representing the core)
• Variable inductor: Inductor with an arrow through it
• Transformer: Two inductors side by side with parallel core lines between them

Switch Symbols

Manual Switches

• SPST (Single-Pole Single-Throw): One movable contact, one fixed contact
• SPDT (Single-Pole Double-Throw): One movable contact, two fixed contacts (3-way switch)
• DPST (Double-Pole Single-Throw): Two ganged SPST switches
• DPDT (Double-Pole Double-Throw): Two ganged SPDT switches

Push Buttons

• Normally Open (NO): Two terminals with a movable bridge, gap in the middle
• Normally Closed (NC): Two terminals with bridge in contact position

Specialized Switches

• Toggle switch: Standard SPST with a lever indicator
• Rotary switch: Multiple position selector
• Limit switch: Mechanical actuator with switch contacts
• Pressure switch: Switch with pressure actuator symbol
• Float switch: Switch with float symbol
• Key switch: Switch with key symbol

Relay and Contactor Symbols

• Relay coil: Circle with a diagonal line (or rectangle with K designation)
• Relay contact NO: Gap in a line (closes when coil is energized)
• Relay contact NC: Line with a bridge (opens when coil is energized)
• Contactor: Similar to relay but with heavier contacts, K designation
• Contactor with overload: Contactor symbol plus thermal overload element
• Timer relay: Relay with timing function indicator

Semiconductor Symbols

Diodes

• Standard diode: Triangle pointing to a line (current flows in triangle direction)
• Zener diode: Diode with bent line at the cathode end
• Schottky diode: Diode with curved line at cathode
• LED (Light Emitting Diode): Diode with arrows pointing away
• Photodiode: Diode with arrows pointing toward it
• Bridge rectifier: Four diodes in a diamond arrangement

Transistors

• NPN BJT: Circle with three leads; arrow on emitter points outward
• PNP BJT: Circle with three leads; arrow on emitter points inward
• N-channel MOSFET: Gate, source, drain with arrow on source
• P-channel MOSFET: Similar with reversed arrow
• JFET: Gate, source, drain with arrow on gate

Thyristors

• SCR (Silicon Controlled Rectifier): Diode with a gate terminal
• TRIAC: Bidirectional thyristor symbol
• DIAC: Bidirectional trigger device

Integrated Circuit Symbols

• Op-amp: Triangle with + and - inputs and one output
• Logic gates: AND, OR, NOT, NAND, NOR, XOR (distinctive shapes in ANSI; rectangles with function labels in IEC)
• 555 Timer: Rectangle with 8 labeled pins
• Voltage regulator: Rectangle with IN, OUT, GND pins
• General IC: Rectangle with pin numbers and labels

Protection Devices

Fuses

• Fuse (ANSI): Small S-curve or thin rectangle with a line through it
• Fuse (IEC): Rectangle with a line through the middle
• Circuit breaker: Switch symbol with a small rectangle (trip mechanism)
• GFCI breaker: Breaker with test button indicator
• AFCI breaker: Breaker with arc-fault indicator

Surge Protection

• MOV (Metal Oxide Varistor): Variable resistor with voltage indicator
• TVS diode: Zener-style symbol
• Surge protector (SPD): Special symbol with lightning bolt

Motor Symbols

• DC motor: Circle with M inside, two terminals
• AC motor (single-phase): Circle with M inside, two or three terminals
• AC motor (three-phase): Circle with M inside, three terminals
• Stepper motor: Motor symbol with step indicators
• Servo motor: Motor symbol with position feedback

Measurement and Indicator Symbols

• Voltmeter: Circle with V inside
• Ammeter: Circle with A inside
• Wattmeter: Circle with W inside
• Ohmmeter: Circle with omega symbol inside
• Indicator lamp: Circle with X inside (or filled circle)
• Buzzer/alarm: Specific buzzer symbol

Connector Symbols

• Plug: Arrow symbol or specific plug outline
• Socket/receptacle: Concave symbol or specific receptacle outline
• Terminal block: Row of connection points
• Wire junction: Dot where wires connect
• No connection: Crossing wires without dot

Residential Wiring Symbols

These symbols are commonly used on architectural floor plans:

• Duplex outlet: Two parallel lines with a semicircle
• GFCI outlet: Outlet symbol with GFI label
• 240V outlet: Outlet symbol with voltage label
• Single-pole switch: S
• 3-way switch: S3
• 4-way switch: S4
• Dimmer switch: SD
• Ceiling light: Circle with lines radiating outward
• Recessed light: Circle with inner circle
• Fluorescent light: Rectangle with lines
• Ceiling fan: Circle with F
• Smoke detector: Circle with SD
• Doorbell: Bell symbol

Industrial Control Symbols

• Contactor (power contacts): Heavy-duty switch contacts with K designation
• Overload relay: Thermal element with heater and contact
• Timer contact (on-delay): Contact with clock symbol
• Timer contact (off-delay): Contact with inverted clock symbol
• PLC module: Rectangle with I/O labels
• Variable Frequency Drive (VFD): Rectangle with motor and frequency labels
• Safety relay: Relay with safety designation
• E-stop button: Red mushroom head pushbutton symbol

Using This Reference with CircuitDiagramMaker

CircuitDiagramMaker includes over 400 professional symbols across four packs:

• DIY Pack (69 symbols): Residential wiring -- outlets, switches, breakers, lights, panels
• Hobbyist Pack (111 symbols): Electronics -- resistors, capacitors, transistors, Arduino, sensors
• Pro Pack (106 symbols): Professional -- contactors, relays, motor starters, transformers
• Industrial Pack (114 symbols): Industrial controls -- VFDs, PLCs, overloads, terminal blocks, safety devices

Every symbol follows IEC/ANSI standards for instant recognition. Search the symbol library by name, browse by category, or use the AI circuit generator to automatically place the correct symbols for your circuit description.

Downloading a PDF Reference

For a printable reference you can keep at your workbench, create a symbol reference diagram in CircuitDiagramMaker:

1. Create a new diagram
2. Place and label every symbol you use regularly
3. Organize by category (power, passive, semiconductor, switches, etc.)
4. Export as PDF for a high-quality printable reference sheet
5. Pin it above your workbench or file it in your project binder

IEC vs ANSI Symbol Comparison Table

Several of the symbol categories above look noticeably different depending on which standard a drawing follows. This table lines up the most common variants side by side:

If a drawing mixes shapes from both columns, it is either following a mixed house standard or was assembled from parts sourced from different regions -- confirm with a legend before assuming which convention applies.

Worked Example: Identifying Symbols in a Simple Lighting Circuit

Consider a basic switched lighting circuit: a duplex outlet, a single-pole switch, and a ceiling light, all fed from a breaker panel. On the schematic, the panel connection starts at a circuit breaker symbol (a switch symbol with a small rectangle). A wire runs from the breaker to the switch symbol -- shown as an S with a break in the line, the open gap meaning the switch is off in its drawn state. From the switch, the wire continues to the ceiling light symbol (a circle with radiating lines). If a duplex outlet is on the same circuit, it appears as a separate branch, not routed through the switch, so it stays energized whether the switch is on or off. Reading the diagram means tracing the unbroken conductive path: breaker to switch to light is one path, and breaker to outlet is a second, independent path. A dot at any junction means the branches are electrically tied together; no dot means the lines simply cross on the page without connecting.

Common Mistakes When Reading Symbol Charts

Treating similar-looking symbols as identical. A standard diode, Zener diode, Schottky diode, and LED all share the same basic triangle-and-bar shape -- the small marks added to the cathode line (bent ends, curved line, or arrows) change the meaning completely. Always check for these details before assuming a generic diode.

Ignoring polarity marks on capacitors. A polarized (electrolytic) capacitor connected backwards can fail or vent. The curved plate in the symbol marks the negative terminal -- do not assume both leads are interchangeable just because a simple two-line capacitor appears elsewhere in the same diagram.

Overlooking the difference between a switch and a relay contact. Both can look like a simple break in a line. A manually operated switch symbol stands alone; a relay or contactor contact symbol is associated with a coil elsewhere on the diagram and is labeled with the same reference designator (K1, K2) as that coil.

Not checking whether NO or NC is the resting state. Every relay, contactor, push button, and limit switch symbol shows its resting (unpowered, unpressed, unactuated) state. Confirm which state that is before wiring or troubleshooting from the diagram.

Conclusion

Electrical symbols are a universal language that enables clear communication between electricians, engineers, and hobbyists worldwide. Learning the common symbols takes practice, but once you know them, you can read and draw any circuit diagram with confidence.

Use CircuitDiagramMaker to practice with real symbols, and keep this reference guide handy for symbols you encounter less frequently.

Access 400+ professional electrical symbols in CircuitDiagramMaker -- free online circuit diagram maker with IEC/ANSI standard symbols.

Frequently asked questions

How do you tell a capacitor symbol apart from a battery symbol?

Both use two parallel lines, but a capacitor's two lines are usually the same length with a small gap between them, unless polarized, in which case one line is curved. A battery symbol alternates long and short lines -- one pair per cell -- with the long line as positive and the short line as negative.

Is there a specific symbol for a blown fuse?

No. Schematic and chart symbols show the fuse in its normal, intact state -- there is no separate graphical symbol for a blown fuse. You determine whether a fuse has blown by testing continuity with a meter or visually inspecting the physical fuse, not by reading the diagram.

Is there a standard symbol for a wireless or antenna connection?

There is no dedicated Wi-Fi symbol in IEC or ANSI electrical standards. RF and wireless connections are typically shown using the antenna symbol -- a line with two angled ticks near the top -- attached to the relevant component, rather than a symbol representing the wireless link itself.

Does the resistor symbol show its resistance value?

No, the zigzag or rectangle shape only identifies the component as a resistor. The actual resistance value, tolerance, and sometimes power rating are written as a text label next to the symbol, for example '1k' or '220R 5%', separate from the symbol shape itself.

Do electrical symbol charts also cover HVAC or plumbing symbols?

No. Electrical symbol charts cover electrical and electronic components only -- wiring, devices, and control components. HVAC ductwork and equipment use a separate mechanical symbol set, and plumbing uses its own pipe and fixture symbols, even though all three may appear together on a combined building drawing set.

Interactive diagrams for this guide

• Circuit Diagram Symbols Class 10
• Electrical Circuit Diagram
• Electrical Diagram

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