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An RLC series circuit contains a capacitor of 12 μF, an inductor of 25 mH, and a resistor of 60 Ω. At what angular frequency does the current oscillate (natural/resonant angular frequency)?

1. 1.2 × 10³ rad/s
2. 1.4 × 10³ rad/s
3. 1.8 × 10³ rad/s
4. 2.2 × 10³ rad/s

Correct answer: 1.8 × 10³ rad/s

Solution

The oscillation angular frequency is ω = 1/sqrt(LC). LC = (25×10⁻³)(12×10⁻⁶) = 3×10⁻⁷. sqrt(LC) = sqrt(3×10⁻⁷) = 5.48×10⁻⁴. ω = 1/5.48×10⁻⁴ = 1.83×10³ rad/s ≈ 1.8 × 10³ rad/s.

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