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Since power is defined as the product of current and voltage, the ampere can alternatively be expressed in terms of the other units using the relationship I = P/V, and thus 1 A = 1 W/V. Current can be measured by a multimeter, a device that can measure electrical voltage, current, and resistance.
An ammeter (abbreviation of ampere meter) is an instrument used to measure the current in a circuit. Electric currents are measured in amperes (A), hence the name. For direct measurement, the ammeter is connected in series with the circuit in which the current is to be measured.
Ampacity is a portmanteau for ampere capacity, defined by United States National Electrical Codes.Ampacity is defined as the maximum current, in amperes, that a ...
where is the current, measured in amperes; is the potential difference, measured in volts; and is the resistance, measured in ohms. For alternating currents , especially at higher frequencies, skin effect causes the current to spread unevenly across the conductor cross-section, with higher density near the surface, thus increasing the apparent ...
Range of currents associated with single ion channels [calcium (1 pA), sodium (10-14 pA), potassium (6 pA)] as measured by patch-clamp studies of biological membranes 10 −5: 10 μA Minimum current necessary to cause death (by ventricular fibrillation when applied directly across the human heart) [1] 10 −4: 700 μA
Symbol [1] Name of quantity Unit name Symbol Base units E energy: joule: J = C⋅V = W⋅s kg⋅m 2 ⋅s −2: Q electric charge: coulomb: C A⋅s I electric current: ampere
SI base units Name Symbol Measure Post-2019 formal definition [1] Historical origin / justification Dimension symbol; second: s time "The second, symbol s, is the SI unit of time.
An electrical meter with integral AC current clamp is known as a clamp meter, clamp-on ammeter, tong tester, or colloquially as an amp clamp. A clamp meter measures the vector sum of the currents flowing in all the conductors passing through the probe, which depends on the phase relationship of the currents. Only one conductor is normally ...