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An ampere-hour or amp-hour (symbol: A⋅h or A h; often simplified as Ah) is a unit of electric charge, having dimensions 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.
An iron cored neon-sign transformer, with a 9-volt battery for scale. A neon-sign transformer (NST) is a transformer made for the purpose of powering a neon sign.They convert mains voltage in the range 120-347 V up to high voltages, in the range of 2 to 15 kV.
The ampere is named for French physicist and mathematician André-Marie Ampère (1775–1836), who studied electromagnetism and laid the foundation of electrodynamics.In recognition of Ampère's contributions to the creation of modern electrical science, an international convention, signed at the 1881 International Exposition of Electricity, established the ampere as a standard unit of ...
It is simple to measure very high currents (hundreds of amperes) with the appropriate current transformer. Accurate measurement of low currents (a few milliamperes) with a current transformer clamp is more difficult. The range of any given meter can be extended by passing the conductor through the jaw multiple times.
Ordinary Weston-type meter movements can measure only milliamperes at most, because the springs and practical coils can carry only limited currents. To measure larger currents, a resistor called a shunt is placed in parallel with the meter. The resistances of shunts is in the integer to fractional milliohm range.
A domestic power supply voltage (110 or 230 V), 50 or 60 Hz alternating current (AC) through the chest for a duration longer than one second may induce ventricular fibrillation at currents as low as 30 milliamperes (mA). [12] [13] With direct current (DC), 90 to 130 mA are required at the same duration. [14]
Mach number (Ma), a measure of speed compared to the speed of sound; Megaampere (MA), a multiple of the SI unit of electric current, the ampere; Megaannum (Ma), one million years; Milliampere (mA), a multiple of the SI unit of electric current, the ampere; Myr, Mya, or Ma, meaning "million years ago"; (NB: broadly equivalent to "Megaannum (Ma ...
For a typical current of 10 mA, g m ≈ 385 mS. The input impedance is the current gain (β) divided by the transconductance. The output (collector) conductance is determined by the Early voltage and is proportional to the collector current. For most transistors in linear operation it is well below 100 μS.