Assertion (A): A backward wave oscillator (BWO) has an internal positive feedback mechanism. Reason (R): Positive feedback is necessary for sustained oscillations. Which of the following is correct?
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ABoth A and R are correct, and R is the correct explanation of A
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BBoth A and R are correct, but R is not the correct explanation of A
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CA is correct but R is wrong
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DA is wrong but R is correct
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EBoth A and R are wrong
Answer
Correct Answer: Both A and R are correct, and R is the correct explanation of A
Explanation
Introduction / Context:A backward wave oscillator (BWO) is a type of vacuum tube oscillator that uses an electron beam interacting with a slow-wave structure. It is important to understand the role of feedback in generating oscillations.
Given Data / Assumptions:
- BWO principle: beam-wave interaction with backward wave propagation.
- Oscillations require feedback to reinforce the signal.
Concept / Approach:
In a BWO, internal positive feedback arises because the backward-traveling wave couples energy back to the electron beam. This feedback sustains oscillations. The reason statement correctly explains why oscillations persist: positive feedback is a fundamental requirement in all oscillators.
Step-by-Step Solution:
Assertion: BWO has internal positive feedback → true.Reason: Positive feedback necessary for oscillations → true.Link: The positive feedback in BWO explains its oscillation mechanism.Verification / Alternative check:
Microwave device theory confirms BWOs operate on backward wave interaction providing feedback for self-oscillation.
Why Other Options Are Wrong:
- Option B: The explanation is indeed correct.
- Option C or D: deny correct parts.
- Option E: both statements are not wrong.
Common Pitfalls:
Confusing feedback in BWO with external cavity feedback in klystrons.
Final Answer:
Both A and R are correct, and R is the correct explanation of A