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If in an A.C. L-C series circuit X_L<X_C, then the current _____ in phase.

Asked in GSEB Board March 2020 (old course) · Phase relationships and phasors

• (1) leads the voltage by π/2
• (2) lags behind the voltage by π/2
• (3) leads the voltage by π
• (4) lags behind the voltage by π

Step-by-step solution

Why the other options are wrong

• (2) That is the inductive case, X_L>X_C. Here the capacitor's reactance is the larger one, so the circuit behaves like a capacitor and the current leads.
• (3) The voltages across L and C are each 90° from the current, so their difference is also 90° from it. A phase difference of π cannot arise from L and C alone.
• (4) The same problem. A lag of π would put the voltage exactly opposite the current, but the net voltage of L and C is always at 90° to it.

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