electrical polarity

{{main|Electric current#Conventions}}

• In electrical engineering, electrical polarity defines the direction in which the electrical current would flow once a source is connected;{{sfn|Graf|1999|p=575}} usually used for the direct current sources, where terminals are traditionally labeled with polarity symbols + (positive) and - (negative), with the conventional current chosen to flow from the positive to negative terminal.
• By analogy, when in electronics a signal is observed across two terminals, the measurement of voltage between the terminals yields opposing signs for the positive and negative polarity.{{sfn|Graf|1999|p=575}}
• In physics and chemistry, electric polarity defines the electric charge separation into positive and negative charges{{sfn|Graf|1999|p=575}} within a system or molecule (for example, water molecules have unequal distribution of electrons between the oxygen and hydrogen atoms{{sfn|Plopper|Ivankovic|2020|p=214}}). The quantitative measure of this separation is called an electric dipole moment.
• In biology, electrical polarity refers to the sign of the difference in electric potential between the parts of a living organism. For example, the inner surface of a cell membrane is usually negatively charged with respect to the outer surface (so called resting potential). When this polarity briefly reverses in a nerve, an opposite action potential is communicated over long distances.{{sfn|Michael|Sircar|2011|p=}}

The binary ("polar") nature of electrical phenomena was known for a very long time, its similarities to the magnetic polarity were driving research on electromagnetism, with Ørsted finally succeeding in finding a link between the electricity and magnetism (Oersted's law) in 1820.{{sfn|Whewell|1858|p=372}} The use of plus and minus signs for the opposing electrical charges was introduced by Georg Christoph Lichtenberg in the 18th century. The terms "positive" and "negative" were introduced by Benjamin Franklin in 1747.{{sfn|Jensen|2005|p=988}}

Berzelius, in his early 19th century work on electrochemistry, used the term "electrical polarity" to explain the chemical reactions. Per Berzelius, while all atoms possessed both positive and negative polarities (electrochemical dualism), the balance depended on an element (with, for example, oxygen being negative and potassium positive), and the reactions were caused by the electrical attraction between the atoms.{{sfn|Jacobsen|2003|p=xxviii}}

• Polarized plug, a non-reversible electrical plug

{{reflist}}

• {{cite book |last=Graf |first=Rudolf F. |title=Modern Dictionary of Electronics |publisher=Elsevier |date=1999-08-11 |isbn=978-0-08-051198-6 |chapter-url=https://www.google.com/books/edition/Modern_Dictionary_of_Electronics/AYEKAQAAQBAJ?hl=en&gbpv=1&pg=PA575 |access-date=2025-06-01|chapter=polarity}}
• {{cite book |last=Jacobsen |first=Anja Skaar |title=H.C. Ørsted's Theory of Force: An Unpublished Textbook in Dynamical Chemistry |publisher=Kgl. Danske Videnskabernes Selskab |date=2003 |isbn=978-87-7876-326-6 |chapter-url=https://www.google.com/books/edition/H_C_%25C3%2598rsted_s_Theory_of_Force/qUpAmoyvxbcC?hl=en&gbpv=1&pg=PR28 |access-date=2025-06-01 | chapter=Hans Christian Ørsted's Chemical Philosophy | pages = vii-xxxii

}}

• {{cite journal |last=Jensen |first=William B. |title=The Origins of Positive and Negative in Electricity |journal=Journal of Chemical Education |volume=82 |issue=7 |date=2005 |issn=0021-9584 |doi=10.1021/ed082p988 |pages=988-989 |access-date=2025-06-01|url=https://homepages.uc.edu/~jensenwb/reprints/125.%20Positive%20&%20Negative.pdf}}
• {{cite book |last=Michael |first=Joel |last2=Sircar |first2=Sabyasachi |title=Fundamentals of Medical Physiology |publisher=Thieme |date=2011-01-01 |isbn=978-1-60406-275-5 |chapter-url=https://www.google.com/books/edition/Fundamentals_of_Medical_Physiology/Cp5WVLGpyZoC?hl=en&gbpv=1&pg=PT92 |access-date=2025-06-01|chapter=Resting Membrane Potential}}
• {{cite book |last=Plopper |first=George |last2=Ivankovic |first2=Diana Bebek |title=Principles of Cell Biology |publisher=Jones & Bartlett Learning |date=2020-02-03 |isbn=978-1-284-21051-4 |chapter-url=https://www.google.com/books/edition/Principles_of_Cell_Biology/pKDHDwAAQBAJ?hl=en&gbpv=1&pg=PA214 |access-date=2025-06-01|chapter=Polarity}}
• {{cite book |last=Whewell |first=William |title=History of Scientific Ideas |publisher=Parker |date=1858 |url=https://www.google.com/books/edition/History_of_Scientific_Ideas/d61RAAAAcAAJ?hl=en&gbpv=1&pg=PA372 |access-date=2025-06-01}}

Category:Outlines of technology and applied science

Category:Electricity

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