Which unit is commonly used to specify the size of a given charge?

The unit commonly used to specify the size of a given electric charge is the coulomb. The coulomb quantifies electric charge and is defined as the amount of electric charge transported by a constant current of one ampere in one second. This measure is foundational in electrical engineering because it helps in understanding and calculating electric phenomena related to current flow, voltage, and capacitance.

In contrast, other units listed serve different purposes in the field of electricity. The volt measures the electric potential difference or electromotive force, indicating how much work is needed to move a charge between two points. The watt is a unit of power that represents the rate of energy transfer; it is calculated as voltage multiplied by current. The ampere, often shortened to amp, measures the flow of electric charge and indicates how much charge passes through a conductor over time. Each of these units plays an important role in understanding electrical systems but does not specifically designate the amount of charge itself.