What Does Watt’s Law State? Evaluate the statement: “Watt’s law states the relationships of power to energy.”
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AFalse
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BTrue
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CTrue only for DC power
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DTrue for reactive power only
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ETrue when time is constant
Answer
Correct Answer: False
Explanation
Introduction / Context:Watt’s law is central to circuit analysis. However, it is frequently misquoted. This question checks whether you can distinguish between power relations (instantaneous rate) and energy (accumulated quantity over time).
Given Data / Assumptions:
- Power P, voltage V, current I, resistance R.
- Energy W relates to power via time integration.
- Linear, time-invariant context for basic formulas.
Concept / Approach:
Watt’s law relates power to voltage, current, and resistance: P = V * I = I^2 * R = V^2 / R (under appropriate conditions). It does not define energy; instead, energy is W = ∫ P dt. Thus, tying Watt’s law directly to power–energy relationships is incorrect.
Step-by-Step Solution:
State Watt’s law: P = V * I (general), and with Ohm’s law, P = I^2 * R or P = V^2 / R.Define energy separately: W = ∫ P dt; for constant P, W = P * t.Therefore, Watt’s law does not state relationships of power to energy; it relates power to electrical variables.Any energy relation requires explicit integration over time, not contained in Watt’s law.Verification / Alternative check:
Textbooks categorize Watt’s law under instantaneous power in circuit analysis, while energy calculations appear in work/energy sections using time integrals or kWh billing examples.
Why Other Options Are Wrong:
Conditional “true” options remain incorrect; Watt’s law never equates or directly relates power to energy. It may be used within energy calculations but is not itself an energy law.
Common Pitfalls:
Assuming that because energy is power times time, Watt’s law somehow includes time; it does not. Keep rate (power) and accumulated quantity (energy) distinct.
Final Answer:
False