Fundamental units — in SI (International System of Units), which unit is the correct unit of electric charge used throughout electronics and physics?
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Aampere
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Bcoulomb
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Cvolt
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Dohm
Answer
Correct Answer: coulomb
Explanation
Introduction / Context:Clear understanding of SI units is essential in circuit analysis, electromagnetics, and instrumentation. Electric charge is a primary quantity from which current, voltage relationships, and capacitor behavior are derived. This item checks if you can identify the proper SI unit for charge.
Given Data / Assumptions:
- Use of SI base and derived units.
- Standard definitions per the SI Brochure.
- No need to convert between systems; just identify the correct unit.
Concept / Approach:The coulomb (symbol C) is the SI unit of electric charge. One coulomb corresponds to the charge transported by a current of one ampere in one second, so 1 C = 1 A * 1 s. Recognizing this definition also connects charge to capacitor equations such as Q = C_elec * V, where Q is charge (C), C_elec is capacitance (F), and V is voltage (V).
Step-by-Step Solution:
Recall the definition of current: I = dQ/dt.Rearrange to Q: Q = ∫ I dt, giving coulombs when amperes are integrated over seconds.Select the unit “coulomb” as the measure of charge.Verification / Alternative check:Capacitor formula Q = C_elec * V uses coulombs on the left when capacitance is in farads and voltage in volts (since 1 F = 1 C/V).
Why Other Options Are Wrong:
- Ampere: Unit of electric current (charge per second), not charge itself.
- Volt: Unit of electric potential difference.
- Ohm: Unit of resistance.
Common Pitfalls:Confusing charge with current due to their close relationship; remember current is the rate of flow of charge.
Final Answer:coulomb