At the end of the quarter, should I write a thank you note to a TA (that taught the class) that has helped me?

A TA wants the students to be genuinely touched by the teaching and retain the material in a deep way, at the expense of any thanks. Because of this, I'd strongly suggest sending it in a paper card - or even note. Email, along with some other sent stuff, seems too off the cuff. Plus he/she can't save it.