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The 2019 revision of the SI defined the ampere by taking the fixed numerical value of the elementary charge e to be 1.602 176 634 × 10 −19 when expressed in the unit C, which is equal to A⋅s, where the second is defined in terms of ∆ν Cs, the unperturbed ground state hyperfine transition frequency of the caesium-133 atom.
In direct current (DC) circuits, this product is equal to the real power, measured in watts. [3] The volt-ampere is dimensionally equivalent to the watt: in SI units, 1 V⋅A = 1 W. VA rating is most used for generators and transformers, and other power handling equipment, where loads may be reactive (inductive or capacitive).
A simple voltage dropper can be used to reduce the voltage for low-power devices; if more than 12V is required, or for high-powered devices, a switched-mode power supply is used. The output will usually be DC in the range 1.5–24 V. Power supplies that output either 100–120 V AC or 210–240 V AC are available; they are called inverters ...
High-speed train overhead power lines: 25 kV at 50 Hz, but see the List of railway electrification systems and 25 kV at 60 Hz for exceptions. High-voltage electric power transmission lines: 110 kV and up (1.15 MV is the record; the highest active voltage is 1.10 MV [9]) Lightning: a maximum of around 150 MV. [10]
Aircraft often use 400 Hz power internally, so 50 Hz or 60 Hz to 400 Hz frequency conversion is needed for use in the ground power unit used to power the airplane while it is on the ground. Conversely, internal 400 Hz internal power may be converted to 50 Hz or 60 Hz for convenience power outlets available to passengers during flight.
1.2 × 10 2: tech: electric power output of 1 m 2 solar panel in full sunlight (approx. 12% efficiency), at sea level 1.3 × 10 2: tech: peak power consumption of a Pentium 4 CPU 2 × 10 2: tech: stationary bicycle average power output [17] [18] 2.76 × 10 2: astro: fusion power output of 1 cubic meter of volume of the Sun's core. [19] 2.9 × 10 2
The henry (symbol: H) is the unit of electrical inductance in the International System of Units (SI). [1] If a current of 1 ampere flowing through a coil produces flux linkage of 1 weber turn, that coil has a self-inductance of 1 henry. The unit is named after Joseph Henry (1797–1878), the American scientist who discovered electromagnetic induction independently of and at about the same ...
Power output = energy / time 1 terawatt hour per year = 1 × 10 12 W·h / (365 days × 24 hours per day) ≈ 114 million watts, equivalent to approximately 114 megawatts of constant power output. The watt-second is a unit of energy, equal to the joule. One kilowatt hour is 3,600,000 watt seconds.