See also: Joule (homonymy)

The joule (symbol: J ) is the unit of energy international Système (IF).

Since energy appears in several forms (Chaleur, Lumière, movement, etc) one finds this unit in several fields such as the Chimie, the Physique and the electronic .

The unit owes its name to the English physicist James Prescott Joule.

One defines this unit as being:

• the work produced by a force of a newton whose point of application moves of a Mètre in the direction of the force:

$1\; J\; =\; 1\; NR\; \backslash \; cdot\; m\; =\; 1\; kg\; \backslash \; cdot\; m^2\; \backslash \; cdot\; s^\; \{-\; 2\}$

• provided work when a running of a amp crosses a resistance of a Ohm during a second:

$1\; J\; =\; 1\; \backslash \; Omega\; \backslash \; cdot\; A^2\; \backslash \; cdot\; S\; =\; 1\; kg\; \backslash \; cdot\; m^2\; \backslash \; cdot\; s^\; \{-\; 2\}\; \backslash ,$

One can think it roughly as necessary work to raise an object such as an apple a one meter height (the apple must then weigh approximately 102 grams):

W = P × H

P = m × γ

W = m . G . H

where:

• W is necessary work in joules (J);
• P is the Poids in newtons (NR);
• m is the mass in kilograms (kg);
• H is the height of rise in meters (m);
• γ or G (gamma) is the Accélération of the Pesanteur, presumedly constant, measures some a second square (m.s^-2).

On the surface of the ground, in France the value of G is 9,81 m/s ², therefore near to 10 m/s ². Another image, less precise numerically would consist in saying than an energy of 1 joule is stored when one goes up a bar of chocolate of 1 m height, if the shelf has well a mass of 100 G.

The force is of 1 NR when the mass is of 1/9,81 kg, that is to say approximately 102 grams.

Conversions

• One a:

1 Calorie = 4,1855 joules. N.B: the calorie is an obsolete unit which one should not any more employ like unit of energy, as well as megacal.

• One notes that the Watt is the unit of power (energy according to time) of the international system, one has then:

1 J = 1 W.s, then

1 kWh = 3.600.000 J (= 3.600.000 W.s)

See too

joule|joule

• James Prescott Joule
• Unit derived from the international system
• Watt
• Kilowatt-hour
• Electric-hour
• Calorie
• Kilowatt-volt

External bonds

• Conversion of joule towards other units of energy
• Conversions into line of joules

Simple: Joule

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