Question

In a parallel resonance circuit, why does the current lag behind the source
voltage at frequencies below resonance?
(a) because the circuit is predominantly resistive
(b) because the circuit is predominantly inductive
(c) because the circuit is predominantly capacitive
(d) none of the above​

Answer 1

Answer:

(b) because the circuit is predominantly inductive

Explanation:

If the source voltage  $V = V_m\sin(\omega t)$

then the current passing through the inductor will be  $I = I_m\sin(\omega t -\frac{\pi }{2} )$

Now we can see if the inductor in the parallel resonance circuit is dominant i.e. the current through the resistor and capacitor is neglected then always the current(I) lags 90° to the source voltage(V).

Therefore, (b) because the circuit is predominantly inductive.

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Answer 2

Answer:

In a parallel resonance circuit,  the current lag behind the source voltage at frequencies below resonance because the circuit is predominantly inductive.

Explanation:

We know that the source voltage is   $V=V_{m} sin(wt)$

Therefore, the current passing through the inductor will be $I=I_{m}sin(wt -\frac{\pi }{2} )$

Hence, the current (I) always lags 90 degrees behind the source voltage  (V) if the inductor in the parallel resonance circuit is dominant, which means that the current via the resistor and capacitor is neglected.

Thus, the circuit is predominantly inductive.

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