On a polarized North American two-blade AC plug, the wider blade is neutral and the narrower blade is hot (line). Neither is properly called positive or negative: those terms usually describe DC polarity, while household AC alternates. This blade convention does not apply to every plug type or region.
How to identify the blades on a polarized North American plug
- Wide blade: neutral.
- Narrow blade: hot, also called line.
The unequal blades are meant to fit a matching receptacle in only one orientation, preserving which appliance conductor connects to hot and which to neutral. If both blades are the same width, appearance alone does not identify hot and neutral.
Why “positive” and “negative” are the wrong terms for household AC
Household alternating current (AC) changes direction periodically, so an ordinary AC plug does not have fixed positive and negative prongs. Use hot and neutral for the conductors in a polarized AC plug.
A DC adapter is different: its output may have a positive and negative terminal, but the blade shape on its AC input does not tell you the DC output polarity. Check the adapter’s polarity marking and the device’s requirements; do not infer them from the plug shape.
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- CLEAR LCD READOUT: GFCI Receptacle Tester features a large backlit LCD readout for easy voltage reading and clear indication of wiring conditions
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Why preserving polarization matters
Polarization helps keep an appliance’s switch and internal wiring on the intended side of the circuit. The U.S. Department of Housing and Urban Development’s rehabilitation guide explains that reversed polarity in a lamp with an Edison screw-shell lampholder can leave the exposed socket energized even when the switch is off. Do not bend, file, or remove a polarized blade to make a plug fit.
Neutral is not ground
Neutral and ground are different conductors and serve different purposes. A grounding terminal or grounding-type device must be reserved for grounding; it is not another name for neutral. On a common NEMA 5-15 receptacle, Schneider Electric identifies green as ground, white as neutral, and black or red as common hot-wire colors, while noting that hot-wire color can vary with the building’s electrical scheme.
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- CLEAR LIGHT SEQUENCE: Outlet tester's light sequence indicates correct/incorrect wiring, ensuring easy identification of wiring issues
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Plug conventions vary by region and connector
The wide-neutral, narrow-hot convention is not universal. ASME notes that Type A plugs are used in North America, Central America, and Japan, but Japanese Type A plugs typically have two narrow blades; the North American version commonly has a wider neutral blade. A similar plug designation does not by itself guarantee compatibility.
The IEC 60884-1:2022 standard covers household AC plugs and socket-outlets within broad rated-voltage and current scope limits, and its catalogue records a corrected version dated July 2026. That standard scope does not establish one blade orientation for every national plug system.
Rank #3
- EFFECTIVE GFCI WIRING PROBLEM DETECTION: GFCI Tester detects common wiring problems in standard and GFCI receptacles, ensuring electrical safety
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- DURABLE AND TOUGH: Built to withstand a 6.6-foot (2m) drop, ensuring durability and reliability in various working conditions
- WIDE OPERATING TEMPERATURE RANGE: Can be used in temperatures ranging from 32-Degree to 140-Degree Fahrenheit (0-Degree to 40-Degree Celsius), offering versatility
- VERSATILE VOLTAGE SUPPORT: Designed for use with 110/125V AC at 50/60Hz in 3-wire outlets, meeting common voltage requirements
When a plug or receptacle does not look right
- Do not force a plug into a receptacle or alter its blades. Use equipment designed for that receptacle and location.
- If you cannot identify the connector or its intended supply, check the appliance documentation or consult a qualified electrician rather than guessing from blade shape.
- If the receptacle’s wiring or condition is in doubt, a plug-in receptacle tester may help with basic checks, but it does not replace professional evaluation of a suspected wiring fault.
For context, Schneider Electric describes a NEMA 5-15 receptacle as a two-pole, three-wire grounding type rated for a maximum of 15 A and 125 V. Those ratings refer to that receptacle type in U.S./Canadian context, not to every plug system.
Quick Recap
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- Multi-functional socket tester with multiple functions, the socket tester's light sequences show different wiring problems to ensure you can easily identify wiring problems
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