A circuit when connected to an AC source of 12 V gives a current of 0.2 A. The same circuit when connected to a DC source of 12 V, gives a current of 0.4 A. The circuit is [2019]

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Solution

Q.
A circuit when connected to an AC source of 12 V gives a current of 0.2 A. The same circuit when connected to a DC source of 12 V, gives a current of 0.4 A. The circuit is [2019]

1 series LR

2 series RC

3 series LC

4 series LCR

Ans.
(1)

When the circuit is connected to an AC source of 12 V, it gives a current of 0.2 A.

$∴$ $Impedance, Z = \frac{12}{0.2} = 60$ $Ω$

When the same circuit is connected to a DC source of 12 V, it gives a current of 0.4 A.

$∴$ $Resistance, R = \frac{12}{0.4} = 30$ $Ω$

As, power factor, $cosϕ = \frac{R}{Z} = \frac{30}{60} = \frac{1}{2} = \cos 60 °$

$\Rightarrow ϕ = 60 °, i.e., current lags behind the emf.$

So, we can conclude that the circuit is a series $L R$ .

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