The power factor of an ac circuit having resistance (R) and inductance (L) connected in series and an angular velocity $\mathrm{\omega }$  is 

• A

  $\mathrm{R}/\mathrm{\omega L}$

• B

  $\mathrm{R}/{({\mathrm{R}}^2+{\mathrm{\omega }}^2{\mathrm{L}}^2)}^{1/2}$

• C

  $\mathrm{\omega L}/\mathrm{R}$

• D

  $\mathrm{R}/{({\mathrm{R}}^2-{\mathrm{\omega }}^2{\mathrm{L}}^2)}^{1/2}$