Half-wave rectifier (ideal diode): Given an input of v(t) = 20 sin(ωt) volts, determine the average (DC) value and the root-mean-square (rms) value of the output voltage.
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AV_avg ≈ 6.37 V and V_rms = 10 V
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BV_avg ≈ 6.37 V and V_rms = 5 V
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CV_avg ≈ 10 V and V_rms = 10 V
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DV_avg ≈ 5 V and V_rms = 5 V
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EV_avg ≈ 8 V and V_rms = 14.14 V
Answer
Correct Answer: V_avg ≈ 6.37 V and V_rms = 10 V
Explanation
Introduction / Context:Half-wave rectifiers pass only one half-cycle of a sinusoid. For an ideal diode, the negative half is completely blocked, leading to standard formulae for the average (DC) and rms output values. This problem reinforces those results for a specific amplitude.
Given Data / Assumptions:
- Input: v(t) = V_m sin(ωt) with V_m = 20 V.
- Ideal diode (no drop), pure half-wave rectification.
- Output taken across the load directly.
Concept / Approach:
For an ideal half-wave rectifier: V_avg = V_m/π and V_rms = V_m/2. These come from integrating the rectified waveform over a full period, remembering that the second half of the cycle is zero.
Step-by-Step Solution:
V_avg = V_m / π = 20 / π ≈ 6.366 V → ≈ 6.37 V.V_rms = V_m / 2 = 20 / 2 = 10 V.Verification / Alternative check:
Compute rms from definition: V_rms^2 = (1/2π) ∫0→π (V_m sinθ)^2 dθ = V_m^2/4 → V_rms = V_m/2, confirming 10 V.
Why Other Options Are Wrong:
- Options listing 5 V for average or rms contradict standard half-wave results.
- Average of 10 V implies full-wave or different amplitude.
- Values like 14.14 V correspond to V_m/√2 of an unrectified sine, not a half-wave output.
Common Pitfalls:
- Forgetting the average is over the full period, not just the conducting half.
- Confusing full-wave with half-wave formulae.
Final Answer:
V_avg ≈ 6.37 V and V_rms = 10 V