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A choke coil (inductor) and a resistor are connected in series across an ac source supplying 130 V. If the voltage across the resistor is 50 V, what is the potential difference across the choke coil?
- 80 V
- 120 V
- 100 V
- 90 V
Correct answer: 120 V
Solution
Because V_R and V_L are in quadrature, V² = V_R² + V_L². Thus V_L = sqrt(130² - 50²) = sqrt(16900 - 2500) = sqrt(14400) = 120 V.
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