In a series RL circuit, 12 V rms is measured across the resistor and 14 V rms is measured across the inductor. The peak value of the source voltage is

$$\eqalign{ & {{\text{E}}_{{\text{rms}}}} = \sqrt {{\text{V}}_{\text{L}}^2} + {\text{V}}_{\text{R}}^2 \cr & \Rightarrow {{\text{E}}_{{\text{rms}}}} = \sqrt {{{12}^2}} + {14^2} = \sqrt {340{\text{V}}} \cr & {{\text{E}}_{{\text{max}}}} = {{\text{E}}_{{\text{rms}}}}\sqrt 2 \cr & {{\text{E}}_{{\text{max}}}} = \sqrt {680{\text{V}}} \cr & \Rightarrow {{\text{E}}_{{\text{max}}}} = 26.0\,{\text{V}} \cr} $$