Units MOC

SI units and derived units. Use this as the quick map for dimensional-analysis sanity checks: every equation should reduce to the same base dimensions on both sides.

Core idea

• SI units define the seven base units by exact constants.
• Derived units are just compact names for base-unit combinations.
• In mechanics, track Kilogram, Metre, and Second first; in electromagnetism, add Ampere and Coulomb.

Base units here

• Second — time, set by caesium transition frequency.
• Metre — length, set by light speed and the second.
• Kilogram — mass, set through Planck’s constant.
• Ampere — electric current, charge flow per second.

Derived units here

• Coulomb — electric charge: ampere-second.
• Newton — force: kilogram metre per second squared.
• Newton-Second — impulse / momentum unit.
• Joule — energy / work: newton metre.
• Watt — power: joule per second.
• Volt — electric potential difference: joule per coulomb.