Ampere hour

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Rechargeable batteries
Top: AA battery (2500 mA·h)
Bottom: AAA battery (1000 mA·h)

An ampere hour or amp hour (symbol Ah; also denoted A·h or A h) is a unit of electric charge, having dimensions of electric current times time, equal to the charge transferred by a steady current of one ampere flowing for one hour, or 3600 coulombs.[1] The commonly seen milliampere hour (mAh or mA·h) is one-thousandth of an ampere hour (3.6 coulombs).

Use[edit]

The ampere hour is frequently used in measurements of electrochemical systems such as electroplating and for battery capacity where the commonly known nominal voltage is dropped.

A milliampere second (mA·s) is a unit of measure used in X-ray imaging, diagnostic imaging, and radiation therapy. This quantity is proportional to the total X-ray energy produced by a given X-ray tube operated at a particular voltage.[2] The same total dose can be delivered in different time periods depending on the X-ray tube current.

An ampere hour is not a unit of energy. In a battery system, for example, accurate calculation of the energy delivered requires integration of the power delivered (product of instantaneous voltage and instantaneous current) over the discharge interval.[3] Generally, the battery voltage varies during discharge; an average value or nominal value may be used to approximate the integration of power.[4]

Other measures of electric charge[edit]

The Faraday constant is the charge on one mole of electrons, approximately equal to 26.8 ampere hours. It is used in electrochemical calculations.

Examples[edit]

  • An AA size dry cell has a capacity of about 2 to 3 ampere hours.
  • Automotive car batteries vary in capacity but a large automobile propelled by an internal combustion engine would have about a 50 ampere hour battery capacity.
  • Since one ampere hour can produce 0.336 grams of aluminium from molten aluminium chloride, producing a ton of aluminium requires transfer of at least 2.98 million ampere hours. [5]

See also[edit]

References[edit]

  1. ^ "Full Conversion Table (sorted by Category)" Allmeasures.com, 2013, webpage: AM-Conversion-table.
  2. ^ X-ray Safety Handbook, 9.0 Terms and Definitions, VirginiaTech Environmental, Health and Safety Services Archived July 23, 2007, at the Wayback Machine.
  3. ^ Efty Abir, Najrul Islam (2016). "How to Calculate Amp Hours – Learn of Convert Watts to Amps". Leo Evans. Retrieved 8 December 2016. 
  4. ^ National Research Council (U.S.) (2004). Meeting the energy needs of future warriors. National Academies Press. p. 27. ISBN 0-309-09261-2. 
  5. ^ T. L. Brown, H. E. Lemay Jr, "Chemistry the Central Science", Prentice-Hall, 1977 ISBN 0-13-128769-9 page 562