Fundamental units in electricity: What is the SI unit of electric charge used in circuit calculations and component specifications?

Introduction / Context:
Correct units are essential when applying equations in electronics. The SI unit of electric charge appears in capacitor sizing, current calculations, and timing circuits. Confusing units leads to errors in design and interpretation of datasheets and measurements.

Given Data / Assumptions:

• The question asks for the fundamental SI unit of charge.

Concept / Approach:
The coulomb (C) is the SI unit of electric charge. One coulomb is the quantity of electricity transported in one second by a current of one ampere, linking directly to Q = I * t. Other units listed measure different quantities: volt (potential), ampere (current), and joule (energy).

Step-by-Step Reasoning:

Verification / Alternative check:
Capacitance definition C_cap = Q / V shows Q in coulombs for a given voltage, reinforcing the standard unit usage in component ratings (e.g., microcoulombs, millicoulombs in pulse circuits).

Why Other Options Are Wrong:

• Volt: unit of electric potential difference.
• Ampere: unit of electric current (rate of charge flow).
• Joule: unit of energy or work.

Common Pitfalls:

• Mixing up current (A) with charge (C); remember current is charge per unit time.

Final Answer:
coulomb