Definition:SI/Energy/Joule

Definition

The joule is the SI unit of energy.

It is defined as being:

the energy transferred to (or work done on) a body when a force of $1$ newton acts on that body in the direction of the force's motion through a distance of $1$ metre

the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second.

Thus:

$1 \, \mathrm J = 1 \, \mathrm N \, \mathrm m$

Conversion Factors

\(\ds \)

\(\)

\(\ds 1\)

joule

\(\ds \)

\(=\)

\(\ds 10^7\)

ergs

Symbol

$\mathrm J$

The symbol for the joule is $\mathrm J$.

Its $\LaTeX$ code is \mathrm J .

Base Units

The SI base units of the joule are:

$\mathrm J := \mathrm {kg} \, \mathrm m^2 \mathrm s^{-2}$

where:

$\mathrm {kg}$ denotes kilograms

$\mathrm m$ denotes metres

$\mathrm s$ denotes seconds (of time).

Source of Name

This entry was named for James Prescott Joule.

Sources

• 1969: J.C. Anderson, D.M. Hum, B.G. Neal and J.H. Whitelaw: Data and Formulae for Engineering Students (2nd ed.) ... (previous) ... (next): $1.$ Units and Abbreviations: $1.2$ SI units $(2)$ Derived units
• 1976: Ralph J. Smith: Circuits, Devices and Systems (3rd ed.) ... (previous) ... (next): Chapter $1$: Electrical Quantities: Definitions and Laws: Definitions: Table $1$-$2$: Important Derived Quantities
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): energy
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): joule
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): energy
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): joule
• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): joule
• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): kinetic energy