The abcoulomb (abC or aC) or electromagnetic unit of charge (emu of charge) is the basic physical unit of electric charge in the centimetre gram second system of units. One abcoulomb is equal to ten coulombs.In the electromagnetic cgs system, electrical current is a fundamental quantity defined via Ampère's law and takes the permeability as a dimensionless quantity (relative permeability) whose value in a vacuum is unity. As a consequence, the square of the speed of light appears explicitly in some of the equations interrelating quantities in this system.
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