Question

The SI and CGS units of energy are joule and erg respectively. How many ergs are equal to one joule ?

Concept of Physics - 1 , HC VERMA , Chapter "Introduction to Physics"

Answer 1

Hello Dear.

Given ⇒ 
S.I. Unit of the Energy = joule [J]
C.G.S. Unit of the Energy = erg.


∵ Work(or Energy) = Force × Displacement

⇒ 1 J = 1 N × 1 m.
⇒ 1 J = 10⁵ Dyne × 1 m.
[∵ 1 N = 10⁵ Dyne]

⇒ 1 J = 10⁵ Dyne × 100 cm.
⇒ 1 J = 10⁷ Dyne cm.
⇒ 1 J = 10⁷ erg.
   [∵ 1 Dyne cm = 1 erg]


Thus, 1 Joule is equals to 10⁷ erg.


Hope it helps.

Answer 2

Hey there!

SI unit of energy = Joule
CGS unit of energy = erg

We know that, Energy = Work * displacement


1 Joule = 1N * 1m
1 Joule = 10^5 dyne * 100 cm
1 Joule = 10^7 dyne * cm
1 Joule = 10^7 erg.

Hope helped!