An ampere hour or amp hour (symbol: A⋅h or A h; often simplified as Ah) is a
unit
Unit may refer to:
Arts and entertainment
* UNIT, a fictional military organization in the science fiction television series ''Doctor Who''
* Unit of action, a discrete piece of action (or beat) in a theatrical presentation
Music
* ''Unit'' (a ...
of
electric charge
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...
, having
dimensions
In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coordin ...
of
electric current multiplied by time, equal to the charge transferred by a steady current of one
ampere flowing for one hour, or 3,600
coulombs.
The commonly seen milliampere hour (symbol: mA⋅h, mA h, simplified as mAh) is one-thousandth of an ampere hour (3.6 coulombs).
Use
The ampere hour is frequently used in measurements of
electrochemical
Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outc ...
systems such as
electroplating and for
battery capacity where the commonly known
nominal voltage
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...
is dropped.
A ''milliampere second'' (mA⋅s) is a unit of measurement used in
X-ray imaging
Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...
, diagnostic imaging, and
radiation therapy
Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radi ...
. It is equivalent to a ''millicoulomb''. This quantity is proportional to the total X-ray energy produced by a given X-ray tube operated at a particular voltage. The same total dose can be delivered in different time periods depending on the X-ray tube current.
To help express
energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...
, computation over charge values in ampere hour requires precise data of voltage: 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. Generally, the battery voltage varies during discharge; an average value or nominal value may be used to approximate the integration of power.
Other measures of electric charge
The
Faraday constant
In physical chemistry, the Faraday constant, denoted by the symbol and sometimes stylized as ℱ, is the electric charge per mole of elementary charges. It is named after the English scientist Michael Faraday. Since the 2019 redefinition of ...
is the charge on one
mole
Mole (or Molé) may refer to:
Animals
* Mole (animal) or "true mole", mammals in the family Talpidae, found in Eurasia and North America
* Golden moles, southern African mammals in the family Chrysochloridae, similar to but unrelated to Talpida ...
of electrons, approximately equal to 26.8 ampere hours. It is also used in electrochemical calculations.
Examples
*An
AA size dry cell has a capacity of about 2,000 to 3,000 milliampere hours.
*An average smartphone battery usually has between 2,500 and 4,000 milliampere hours of electric capacity.
*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.
See also
*
Electrochemical equivalent
The Electrochemical equivalent, sometimes abbreviated Eq or Z, of a chemical element is the mass of that element (in grams) transported by 1 coulomb of electric charge. The electrochemical equivalent of an element is measured with a voltameter
...
*
Kilowatt hour (kWh)
References
Units of electrical charge
Non-SI metric units
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