Electrical fundamentals — confirm the unit of power Is the watt (W) the SI unit used to express power in electric circuits and systems?

Introduction / Context:
The term power appears everywhere in electrical engineering, from household appliances to industrial drives. This question checks whether you recognize the correct SI unit for power and understand how it relates to voltage and current in direct current and alternating current contexts.

Given Data / Assumptions:

• We use standard SI units throughout.
• Power in electrical systems is the rate of energy transfer per unit time.
• Real power, reactive power, and apparent power are distinguished by their units and definitions.

Concept / Approach:
In SI, power is measured in watts (symbol W). One watt equals one joule per second. In electric circuits, instantaneous power p(t) equals v(t) * i(t). For resistive direct current circuits, P = V * I = I^2 * R = V^2 / R. In alternating current with sinusoidal steady state, average (real) power is P = V_rms * I_rms * cos(phi), where phi is the phase angle between current and voltage. Despite added concepts such as reactive and apparent power, the unit “watt” specifically refers to real power only.

Step-by-Step Solution:

Verification / Alternative check:
Check equipment nameplates: heaters and lamps list ratings in W or kW for real power; transformers list kVA for apparent power, underlining that “watt” is the specific unit for real power delivery.

Why Other Options Are Wrong:

• “False” would imply another unit (e.g., VA or var) is the unit of power. VA and var are related but represent apparent and reactive power, not real power.

Common Pitfalls:
Confusing watts (real power) with volt-amperes (apparent). Always match the unit to the physical quantity: W for P, var for Q, VA for S.

Final Answer:
True