What are the effects of rhetorical question?

Answer 1

Rhetorical questions encourage the listener to think about what the (often obvious) answer to the question must be. :)

AND

Rhetorical questions make the audience think about an answer to the question but no response is needed. This makes the reader think of all the possible answers, which then becomes memorable to them.

Answer 2

Rhetorical questions can engage the audience, stimulate critical thinking, emphasize a point, and encourage reflection. They are often used to make a strong statement or to draw attention to a particular idea without expecting a direct response.