Hello.
Is it possible to dictate text in search bar of google.com 's front page?
Yes. You can select the search box by using tags or click [current text in the search box if there is any]. Then use either “dictate *” or dictation mode. “dictate *” is better suited for this as it keeps you in normal mode and is faster then switching modes.
Then you can say “submit” - the equivalent of pressing enter.