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QPages 330-331: Q4: HC Verma: Concepts of Physics - Volume 2 Alternating Current Pages 330-331: Q4 Solution: An electric bulb is designed to operate at 12 volts DC. If this …

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often mistakenly equate the DC voltage directly to the peak AC voltage, ignoring that brightness depends on power dissipation. Remember that for normal brightness, the RMS voltage must match the DC rating, requiring the peak voltage to be $\sqrt{2}$ times higher.

An electric bulb is designed to operate at 12 volts DC. If this bulb is connected to an AC source and gives normal brightness, what would be the peak voltage of the source?

Step-by-Step Verified Solution

**Answer:**

E_0 \approx 17 \, \text{V}

. **Step-by-Step Explanation:** For normal brightness, the rms voltage of the AC source must equal the DC voltage:

E_{rms} = 12 \, \text{V}

. Thus,

E_0 = \sqrt{2} \times 12 \approx 16.97 \, \text{V}

[citation:6].

All Questions in this Chapter

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