An ac voltage is applied to a resistance R and inductor L in series. If Rand the inductive reactance are both equal to 3 $\mathrm{\Omega }$, the phase difference between the applied voltage and the current in the circuit is :

• A

  $\frac{\mathrm{\pi }}{6}$

• B

  $\frac{\mathrm{\pi }}{4}$

• C

  $\frac{\mathrm{\pi }}{2}$

• D

  Zero