Electrical energy

Relation between power and energy in permanent mode

A contribution of electrical energy to an electrotechnical system is necessary so that it carries out a work: to move a load, to provide light, to calculate. This work is proportional to the quantity of electricity.

$W=Q\; \backslash \; Delta\; V\; \backslash ,$

W in joules, Q in coulombs and V in Volt S, the potential difference between two points.

With, $Q=I\; \backslash \; cdot\; T\; \backslash ,$ the quantity of electricity:

$W=\; \backslash \; Delta\; V\; \backslash \; cdot\; I\; \backslash \; cdot\; T\; =\; P\; \backslash \; cdot\; T\; \backslash ,$

P the power in Watt S.

Note: Another practical unit is used: $1\; =10^3\; \backslash \; cdot\; 3600\; =\; 3,6\; \backslash \; cdot\; 10^6\; =\; 3,6$ knowing that $1\; =\; 1\; \backslash \; cdot\; 1$

Law of Joule

The Joule effect corresponds to the heat emission of a resistor traversed by a current. For a resistor of resistance $R$ crossed by a current of intensity $i$, $P\; =\; R\; \backslash \; cdot\; i^2\; =\; P\_J$ Thus: $W\; =\; R\; \backslash \; cdot\; i^2\; \backslash \; cdot\; t$ with $W$ in Joules, $R$ in Ohms, $i^2$ in “Amp-square” and $t$ in seconds.

See too

• Energy
• Nuclear energy
• Renewable energy
• Primary energy

Simple: Electrical energy

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