# Erg (unit)

Physical unit
Unit name erg
Unit symbol ${\ displaystyle \ mathrm {erg}}$
Physical quantity (s) Energy (e.g. work , internal energy , heat )
Formula symbol ${\ displaystyle E; \, W; \, U; \, Q}$
dimension ${\ displaystyle {\ mathsf {M \; L ^ {2} \; T ^ {- 2}}}}$
system CGS system of units
In SI units ${\ displaystyle \ mathrm {1 \, erg = 0 {,} 1 \; \ mu J}}$
${\ displaystyle \ mathrm {= 1 \ cdot 10 ^ {- 7} \; {\ frac {kg \, m ^ {2}} {s ^ {2}}}}}$
In CGS units ${\ displaystyle \ mathrm {1 \, erg = 1 \; {\ frac {cm ^ {2} \, g} {s ^ {2}}}}}$
Derived from dyn , centimeters

The erg ( unit symbol : erg; from Greek ἔργον , ergon , work ) is a unit of measurement in the CGS system of units for energy . The unit is widely used in astrophysics and sometimes mechanics .

Except for a power of ten, the erg corresponds to the unit joule , which is common in the MBS- based International System of Units (SI) :

{\ displaystyle {\ begin {aligned} 1 \ \ mathrm {erg} & = \ mathrm {0 {,} 1 \ \ mu J = 1 \ cdot 10 ^ {- 7} J} \\\ Leftrightarrow 10 ^ {7 } \ \ mathrm {erg} & = 1 \ \ mathrm {J} \ end {aligned}}}

Considering the dimensions of the energy provides a dimension

 energy = Force x length = Mass · acceleration · length = Mass (length / time) 2

and therefore the unit in the cgs system

{\ displaystyle {\ begin {aligned} 1 \ \ mathrm {erg} & = \ mathrm {1 \ g \ cdot \ left ({\ frac {cm} {s}} \ right) ^ {2}} \\ & = \ mathrm {1 \ dyn \ cdot \ cm} \ end {aligned}}}

with the Dyn .

In Germany, the Erg is no longer a legal unit since January 1, 1978 .