1 erg is equal to __________ joule.

We know

1 joule $={10}^7\text{erg}$

We get

1 erg $=\frac{1}{{10}^7}$ joule

1 erg 

The erg is a small unit of energy in the centimeter-gram-second (CGS) system, while the joule is the standard unit of energy in the International System of Units (SI).

The erg was commonly used in physics to express small amounts of energy, especially in fields like thermodynamics and electromagnetism. However, due to the widespread adoption of the SI system, the joule has become the preferred unit for energy.

To understand the conversion, consider that 1 erg is a very small amount of energy. It is equal to the energy transferred when a force of 1 dyne (the CGS unit of force) acts over a distance of 1 centimeter. On the other hand, 1 joule is the energy transferred when a force of 1 newton (the SI unit of force) acts over a distance of 1 meter. Since a newton is much larger than a dyne and a meter is much larger than a centimeter, the conversion factor between erg and joule reflects the relative difference in size between these two units.

Thus, when you multiply 1 erg by 10^−7, you get the equivalent energy in joules, which is a much larger and more commonly used unit., you get the equivalent energy in joules, which is a much larger and more commonly used unit.