An AC sine wave has an instantaneous value of current of 11.917A at 37°. What is the RMS value of current? A. 14A В. 13А С. 12A D. 11A
An AC sine wave has an instantaneous value of current of 11.917A at 37°. What is the RMS value of current? A. 14A В. 13А С. 12A D. 11A
Introductory Circuit Analysis (13th Edition)
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ISBN:9780133923605
Author:Robert L. Boylestad
Publisher:Robert L. Boylestad
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![### AC Sine Wave RMS Value Calculation
**Question:**
An AC sine wave has an instantaneous value of current of 11.917A at 37°. What is the RMS value of current?
**Options:**
A. 14A
B. 13A
C. 12A
D. 11A
---
**Explanation:**
To solve this problem, we need to understand the relationship between the instantaneous value, peak value, and RMS (Root Mean Square) value of a sine wave.
For a pure sine wave, the relationship between the instantaneous value (I), peak value (I_peak), and RMS value (I_RMS) is given by:
\[ I = I_{\text{peak}} \cdot \sin(\theta) \]
where:
- \( I \) is the instantaneous current,
- \( I_{\text{peak}} \) is the peak current,
- \( \theta \) is the phase angle.
In this case:
- \( I = 11.917 \text{A} \),
- \( \theta = 37^\circ \).
So,
\[ 11.917 = I_{\text{peak}} \cdot \sin(37^\circ) \]
The sine of 37 degrees (sin 37°) is approximately 0.6018.
\[ 11.917 = I_{\text{peak}} \cdot 0.6018 \]
Solving for \( I_{\text{peak}} \),
\[ I_{\text{peak}} = \frac{11.917}{0.6018} \]
\[ I_{\text{peak}} \approx 19.80 \text{A} \]
The RMS value of the current for a sine wave is:
\[ I_{\text{RMS}} = \frac{I_{\text{peak}}}{\sqrt{2}} \]
Substituting \( I_{\text{peak}} \approx 19.80 \text{A} \),
\[ I_{\text{RMS}} = \frac{19.80}{\sqrt{2}} \]
\[ I_{\text{RMS}} \approx 14 \text{A} \]
Therefore, the correct answer is:
#### **A. 14A**](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F02026046-f334-4297-9417-2971e130f16a%2Fe0a3c8b9-9b22-442d-ba78-c79b16b5b9d7%2F3xbiugg_processed.jpeg&w=3840&q=75)
Transcribed Image Text:### AC Sine Wave RMS Value Calculation
**Question:**
An AC sine wave has an instantaneous value of current of 11.917A at 37°. What is the RMS value of current?
**Options:**
A. 14A
B. 13A
C. 12A
D. 11A
---
**Explanation:**
To solve this problem, we need to understand the relationship between the instantaneous value, peak value, and RMS (Root Mean Square) value of a sine wave.
For a pure sine wave, the relationship between the instantaneous value (I), peak value (I_peak), and RMS value (I_RMS) is given by:
\[ I = I_{\text{peak}} \cdot \sin(\theta) \]
where:
- \( I \) is the instantaneous current,
- \( I_{\text{peak}} \) is the peak current,
- \( \theta \) is the phase angle.
In this case:
- \( I = 11.917 \text{A} \),
- \( \theta = 37^\circ \).
So,
\[ 11.917 = I_{\text{peak}} \cdot \sin(37^\circ) \]
The sine of 37 degrees (sin 37°) is approximately 0.6018.
\[ 11.917 = I_{\text{peak}} \cdot 0.6018 \]
Solving for \( I_{\text{peak}} \),
\[ I_{\text{peak}} = \frac{11.917}{0.6018} \]
\[ I_{\text{peak}} \approx 19.80 \text{A} \]
The RMS value of the current for a sine wave is:
\[ I_{\text{RMS}} = \frac{I_{\text{peak}}}{\sqrt{2}} \]
Substituting \( I_{\text{peak}} \approx 19.80 \text{A} \),
\[ I_{\text{RMS}} = \frac{19.80}{\sqrt{2}} \]
\[ I_{\text{RMS}} \approx 14 \text{A} \]
Therefore, the correct answer is:
#### **A. 14A**
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