Duty cycle statement check: In a pulse waveform, the duty factor is defined as the ratio T/d (period over pulse width). Is this statement correct?
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ATrue
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BFalse
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CTrue only for symmetric pulses
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DFalse unless pulses are aperiodic
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EDepends on rise time
Answer
Correct Answer: False
Explanation
Introduction / Context:The duty factor (also called duty cycle) is a basic descriptor of periodic pulse trains, widely used in sampling, switching power converters, digital logic timing, and pulse-width modulation. Knowing its correct definition avoids design and interpretation errors.
Given Data / Assumptions:
- A periodic pulse train with period T and on-time (pulse width) d.
- Duty factor commonly expressed as a fraction or percentage.
- Rise/fall times are not part of the ideal definition.
Concept / Approach:
By definition, duty factor D = (pulse width) / (period) = d / T. When expressed in percent, Duty % = 100 × (d/T). The inverse T/d is not the duty factor; it is simply the reciprocal and has different engineering meaning (average switching cycles per on-duration).
Step-by-Step Solution:
Identify variables: period T; on-time d.Definition: Duty factor D = d / T (0 ≤ D ≤ 1).Given statement claims D = T / d, which is the reciprocal and therefore incorrect.Hence, the correct evaluation of the statement is False.Verification / Alternative check:
Check extreme cases: If the signal is always on (d = T), D = 1 (100%). The reciprocal T/d would give 1 also here, but for small on-times (e.g., d = T/10), D = 0.1 (10%) while T/d = 10, clearly not a proper duty factor.
Why Other Options Are Wrong:
- True or conditional statements (symmetric pulses, aperiodic) do not change the definition.
- Dependence on rise time: ideal duty factor definition does not include edge slopes.
Common Pitfalls:
- Confusing duty cycle with its reciprocal, particularly when computing average values in PWM converters.
- Mixing up frequency f = 1/T with duty factor d/T.
Final Answer:
False