jquery - Set select option 'selected', by value

I have a select field with some options in it. Now I need to select one of those options with jQuery. But how can I do that when I only know the value of the option that must be selected?

I have the following HTML:

  
    Val 1

    Val 2
    Val 3
  

I need to select the option with value val2. How can this be done?

Here's a demo page:
http://jsfiddle.net/9Stxb/

Answer

There's an easier way that doesn't require you to go into the options tag:

$("div.id_100 select").val("val2");

Check out the this jQuery method.