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Question
Which of the following statements about a series LCR circuit connected to an ac source is correct?
Options
If the frequency of the source is increased, the impedance of the circuit first decreases and then increases.
If the net reactance (XL - XC) of the circuit becomes equal to its resistance, then the current leads the voltage by 45°.
At resonance, the voltage drop across the inductor is more than that across the capacitor.
At resonance, the voltage drop across the capacitor is more than that across the inductor.
Solution
If the net reactance (XL - XC) of the circuit becomes equal to its resistance, then the current leads the voltage by 45°.
Explanation:
For an LCR circuit,
`tanphi = (X_L - X_C)/R`
If XL - XC = R
`tanphi = R/R`
`tanphi = 1 ⇒ phi = 45^circ`
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