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

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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**
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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