Polarised capacitor symbol

A capacitor with one curved plate and a plus mark.

Also known as: Electrolytic capacitor symbol, Polarized capacitor

Engineering & technicalStandard profile

Meanings

An electrolytic capacitor has a right way round, marked by one curved plate or a filled bar and usually a plus sign. Fitting one backwards can make it vent or burst, which is why the polarity marking is drawn rather than left to the part number.

Officially standardisedVerified fact
Denotes a capacitor that must be connected the correct way round, one plate being marked as positive.
Contexts: Technical drawing, Electrical equipment
Officially standardisedVerified fact
Is drawn with one straight plate and one curved plate, the curved plate being the negative side, or with a filled bar in the North American convention.
Contexts: Technical drawing, Electrical equipment
Common modern usageVerified fact
Marks a real hazard rather than a preference: a reversed electrolytic capacitor can vent or rupture in service.
Contexts: Technical drawing, Electrical equipment

Visual description

Two parallel plates, one straight and one curved away from it, with a small plus sign beside the straight plate.

Symmetry: none
Orientation: upright

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

ANSI Y32.2 / IEEE 315, Graphic Symbols for Electrical and Electronics Diagrams
IEEE / American National Standards Institute · retrieved 2026-08-22
Paywalled and NOT READ in full. Registered so the zig-zag resistor familiar from American schematics can be attributed to the standard that defines it, rather than described as the 'old' or 'wrong' form. See docs/paywalled-standards.md.
Electronic symbol
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.
IEC 60617, Graphical symbols for diagrams
International Electrotechnical Commission · retrieved 2026-08-22
Maintained as an online database and NOT READ in full. Registered so a circuit-diagram record can say which body defines its symbol, and so the divergence between the IEC form and the older American form can be recorded as a real standards difference rather than a drawing preference. See docs/paywalled-standards.md.
Circuit diagram
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.

Last reviewed 2026-08-23

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Meanings

Officially standardisedVerified fact

Denotes a capacitor that must be connected the correct way round, one plate being marked as positive.

Contexts: Technical drawing, Electrical equipment

Officially standardisedVerified fact

Is drawn with one straight plate and one curved plate, the curved plate being the negative side, or with a filled bar in the North American convention.

Contexts: Technical drawing, Electrical equipment

Common modern usageVerified fact

Marks a real hazard rather than a preference: a reversed electrolytic capacitor can vent or rupture in service.

Contexts: Technical drawing, Electrical equipment

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

ANSI Y32.2 / IEEE 315, Graphic Symbols for Electrical and Electronics Diagrams
IEEE / American National Standards Institute · retrieved 2026-08-22
Paywalled and NOT READ in full. Registered so the zig-zag resistor familiar from American schematics can be attributed to the standard that defines it, rather than described as the 'old' or 'wrong' form. See docs/paywalled-standards.md.
Electronic symbol
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.
IEC 60617, Graphical symbols for diagrams
International Electrotechnical Commission · retrieved 2026-08-22
Maintained as an online database and NOT READ in full. Registered so a circuit-diagram record can say which body defines its symbol, and so the divergence between the IEC form and the older American form can be recorded as a real standards difference rather than a drawing preference. See docs/paywalled-standards.md.
Circuit diagram
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.

Last reviewed 2026-08-23