question_answer

Assertion             :       An inductance and a resistance are connected in series with an ac circuit. In this circuit the current and the potential difference across the resistance lag behind potential difference across the inductance by an angle p/2. Reason                 :   In LR circuit voltage leads the current by phase angle which depends on the value of inductance and resistance both.

A)             If both assertion and reason are true and the reason is the correct explanation of the assertion.

B)             If both assertion and reason are true but reason is not the correct explanation of the assertion.

C)             If assertion is true but reason is false.

D)             If the assertion and reason both are false.

E)             If assertion is false but reason is true.

Correct Answer: B

Solution :

                   As both the inductance and resistance are joined in series, hence current through both will be same. But in case of resistance, both the current and potential vary simultaneously, hence they are in same phase.  In case of an inductance when current is zero, potential difference across it is maximum and when current reaches maximum (at w t = p/2), potential difference across it becomes zero i.e. potential difference leads the current by p/2 or current lags behind the potential difference by p/2, Phase angle in case of LR circuit is given as \[\varphi ={{\tan }^{-1}}\left( \frac{\omega L}{R} \right)\].