Energy–power linkage — unit equivalence: The number of joules used in 1 second is always equal to the number of _______. (Hint: energy per unit time.)

Introduction / Context:
Power quantifies the rate at which energy is transferred or converted. In SI, one watt is defined as one joule per second. Recognizing this equivalence helps in quickly converting between energy and power in specifications and calculations.

Given Data / Assumptions:

• Energy is measured in joules (J).
• Time interval is 1 second (s).
• We want the unit that equals J/s.

Concept / Approach:
Power P is defined as P = energy / time. Therefore, when 1 joule is used each second, the rate is 1 watt. The other listed units measure different quantities: siemens (conductance), coulombs (charge), amperes (current).

Step-by-Step Solution:

Verification / Alternative check:
Check dimensional consistency: 1 W = 1 N·m/s = 1 kg·m^2/s^3, aligning with joule-per-second identity.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing power with energy (watt-hours vs watts); mixing up ampere (A) with watt (W).

Final Answer:
watts