What is the main tension in Prospero and Ariel's relationship in Act I, Scene 2 of The Tempest and how does Shakespeare create this tension?
The primary tension between Prospero and Ariel comes from the power dynamic between them, and between Ariel's desire for freedom. That is to say, Ariel wants to be free, but is bound to serve Prospero, and does not believe he'll keep his promises and release her (it?) from service.
As far as a quotation regarding this, look at the speech including the statement "Remember I have done thee worthy service" (and the lines before and after).