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This is the definition declared in the modern International System of Units in 1960. [13] The definition of the joule as J = kg⋅m 2 ⋅s −2 has remained unchanged since 1946, but the joule as a derived unit has inherited changes in the definitions of the second (in 1960 and 1967), the metre (in 1983) and the kilogram . [14]
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: A = C/s = W/V A J electric current density: ampere per square metre A/m 2: A⋅m −2: U, ΔV; Δϕ; E, ξ potential difference; voltage; electromotive force: volt: V = J/C kg⋅m 2 ⋅s −3 ⋅A ...
A unit of electrical energy, particularly for utility bills, is the kilowatt-hour (kWh); [3] one kilowatt-hour is equivalent to 3.6 megajoules. Electricity usage is often given in units of kilowatt-hours per year or other periods. [4] This is a measurement of average power consumption, meaning the average rate at which energy is transferred ...
It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540 × 10 12 Hz, K cd, to be 683 when expressed in the unit lm W −1, which is equal to cd sr W −1, or cd sr kg −1 m −2 s 3, where the kilogram, metre and second are defined in terms of h, c and ∆ν Cs."
Yearly electricity production in the U.S. as of 2009 [204] [205] 5×10 19 J: Energy released in 1 day by an average hurricane in producing rain (400 times greater than the wind energy) [179] 6.4×10 19 J: Yearly electricity consumption of the world as of 2008 [206] [207] 6.8×10 19 J: Yearly electricity generation of the world as of 2008 [206 ...
Many compound units for various kinds of rates explicitly mention units of time to indicate a change over time. For example: miles per hour, kilometres per hour, dollars per hour. Power units, such as kW, already measure the rate of energy per unit time (kW=kJ/s). Kilowatt-hours are a product of power and time, not a rate of change of power ...
Energy; system unit code (alternative) symbol or abbrev. notes sample default conversion combinations SI: yottajoule: YJ YJ 1.0 YJ (2.8 × 10 17 kWh) zettajoule: ZJ ZJ 1.0 ZJ (2.8 × 10 14 kWh)
The term temporal frequency is used to emphasise that the frequency is characterised by the number of occurrences of a repeating event per unit time. The SI unit of frequency is the hertz (Hz), [4] named after the German physicist Heinrich Hertz by the International Electrotechnical Commission in 1930.