A graph of the 230 volt 50 Hz electrical mains voltage as a function of time; the root-mean-square voltage is 230 V, but the peak value is sqrt(2) times larger.
<a href="//commons.wikimedia.org/wiki/User:Pieter_Kuiper" title="User:Pieter Kuiper">Pieter Kuiper</a>
<span class="int-own-work" lang="en">Own work</span>